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Program and abstracts of the workshop

Regulation of soil organic matter and nutrient turnover in agriculture

Workshop on 11th and 12th of November 2015 in Witzenhausen,

Germany

Room: Zeichensaal (Steinstraße 19 / Convent Building)

The Workshop was granted by the Deutsche Forschungsgemeinschaft (GRK 1397)

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Background

The regulation of the budget of soil organic matter (SOM) and nutrients by management is a

central focus in agriculture, especially in organic agriculture. The budgets of SOM and nutrients

determine soil fertility, i.e. the long-term productivity of soils. However, the underlying processes

of soil fertility in organic agriculture are not well understood. Therefore, the interdisciplinary

research project deals within the scope of 11 PhD theses with the possibilities to regulate soil

organic matter and nutrient budgets by soil management, crop rotation and by feeding

strategies, via the quality of the manure. The results of the third phase of the Research Training

Group 1397 and investigations of other scientists will be presented and discussed within the

conference workshop.

Topics of the workshop and speakers

Session I Soil organic matter and nutrient dynamics in agriculture Dr. Cornelia Rumpel, French National Centre for Scientific Research, Biogeochemistry and

Ecology on the Earth Surface

Prof. Dr. Yakov Kuzyakov, Georg-August-University Göttingen, Department of Soil Science of

Temperate Ecosystems, Department of Agricultural Soil Science

Session II

Organic amendments in agriculture

Prof. Dr. Bruno Glaser, Martin-Luther-University Halle-Wittenberg, Department of Soil Science

of Temperate Ecosystems

Session III

Methods in soil organic matter research

Prof. Dr. Michael Vohland, University of Leipzig, Geoinformatics and Remote Sensing

Prof. Dr. Hans-Peter Piepho,University of Hohenheim, Institute of Biostatistics and Institute of

Cropscience

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List of Contents

Time Schedule ............................................................................................................................................... 6

Wednesday, 11th November 2015 ............................................................................................................. 6

Thursday, 12th November 2015 ................................................................................................................. 7

Session I: Soil organic matter and nutrient dynamics in agriculture ............................................................. 9

Keynote lecture:

Rumpel, C.: “Land-management effects on soil organic matter composition and nutrient forms” ....... 10

Macdonald, A.; Powlson, D.; Poulton, P.; Glendining, M.; Whitmore, A.; Watts, C. and Goulding, K.:

“The value of soil organic matter in arable cropping systems – insights from the Rothamsted Long-

term Experiments” .................................................................................................................................. 11

Heitkamp, F. & Wendland, M.: “The Rothamsted carbon model fails to simulate carbon stock dynamics

in high input treatments of the long-term trial at Puch, Germany” ....................................................... 12

Strücker, J. & Joergensen, R.G.:“Biotic and abiotic factors controlling carbon dynamics in subsoil” ..... 13

Fiener, P.: “Mitigating infield soil organic carbon erosion – a landscape scale source or sink of CO2?” 14

Brock, C. & Naseem, A.: “Quantitative evidence for soil organic matter services” ................................ 15

Kaiser, M.; Piegholdt, C.; Andruschkewitsch, R.; Linsler, D.; Koch, H-J. and Ludwig, B.: “Influence of

tillage intensity on C and N pools of different turnover kinetics in surface and subsurface soils” ........ 16

Faust, S.; Koch, H.-J. and Joergensen, R.G.: “Effects of tillage intensity on the interaction of soil

moisture, temperature and microbial turnover” .................................................................................... 17

Nüsse, A.M.; Linsler, D.; Reinsch, T.; Loges, R.; Taube, F. and Ludwig, B.: “Impact of cutting and

fertilization regimes on SOC and Nt storage in a temperate grassland soil” ........................................... 18

Ebeling, D.; Tonn, B. and Isselstein, J: “Efficiency of pasture utilization - Gross and net pasture

productivity of heterogeneous swards under different grazing intensities” .......................................... 19

Keynote lecture:

Kuzyakov, Y: “Effects of elevated CO2 on soil C and N turnover” ........................................................... 20

Buchen, C.; Benke, M; Flessa, H.; Gensior, A.; Helfrich, M.; Kayser, M. and Well, R.: “Greenhouse gas

fluxes and mineral N dynamics following grassland renewal or conversion to arable land” ................. 21

Wichern, F., in ‘t Zandt, D.; Arico, A.; Lehnert, D.; Cleven, M.; Kanders, M.J.; Berendonk, C. and Fritz, C.:

“Cover crop effects on soil fertility and nitrogen dynamics” .................................................................. 22

Tendler, L.: “Cover cropping as a mean to close nutrient cycles in German intensively manged farming

systems” .................................................................................................................................................. 23

Anisimova, M.; Heinze, S.; Chen, Y.; Tarchitzky, J. and Marschner, B.: “Priming effects in Israeli soils:

impacts of treated wastewater and freshwater irrigation.” ................................................................... 24

Postersession ............................................................................................................................................... 25

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P1 Inger Struck: “No-till maize as an alternative sowing practice to conventional ploughing. Effects on

GHG-emissions“ ....................................................................................................................................... 26

P2 Amanda Araujo de França: “Interaction of soil and organic fertilizer enriched with 15 N an

overview“ ................................................................................................................................................ 27

P3 Friederike Gnädinger: “Challenges in phenotyping maize: How to detect nitrogen use efficiency of

different maize cultivars“ ........................................................................................................................ 28

P4 Muhammad Shahbaz: “High rate of residue addition decreases C stabilization efficiency due to

priming and low physical protection“ ..................................................................................................... 29

P5 Thorsten Scheile: “Influence of excreta patches on biomass growth and selectivity of grazing

animals in low-input pastures“ ............................................................................................................... 30

P6 Dora Neina: “Estimating mineralizable N of organic materials in tantalite mine soils“..................... 31

P7 Alberto Andrino de la Fuente: “Solanum lycoperisicum L. carbon investment on Rizophagus

irregularis under different accessible P sources“ .................................................................................... 32

P8 Paulo Trazzi: “Different particle sizes and amounts of pinus chip biochar in Pinus teada L. initial

growth“ .................................................................................................................................................... 33

P9 M. Hossininia: “Response of saline calcareous soil to gypsum and sulfuric acid application“ .......... 34

P10 Callum Benfield: “Determination of microbial community structure in subsoil biopores of different

genesis by PLFA and amino sugar analyses“ ........................................................................................... 35

P11 Marina Anisimova: “Enzymatic activity in urban soils affected by anthropogenic influences on the

example of Rostov agglomeration“ ......................................................................................................... 36

P12 Ulf Schneidewind: “Indicators for carbon cycling in organic or conventionally managed cocoa

production systems in Alto Beni, Bolivia“ ............................................................................................... 37

P13 Wiebke Niether: “Organic cocoa production: a sustainable alternative?“ ...................................... 38

Session II: Organic amendments in agriculture ........................................................................................... 39

Keynote lecture:

Glaser, B.: “Biochar Actions in the Environment” ................................................................................... 40

Gronwald, M.; Vos, C.; Don, A. and Helfrich, M.: “Biochar stability in agricultural soils during a 19-

month field incubation in Northern Germany, using natural 13C-abundance” ....................................... 42

Grunwald, D.; Kaiser, M.; Bamminger, C.; Poll, C; Marhan, S. and Ludwig, B.: “Influences of elevated

soil temperature and biochar application on different carbon pools of a loess soil” ............................. 43

Ramadhan, M. R.; Joergensen, R.G and Schlecht, E.: “Effects of water restriction on microbial biomass

in goat faeces” ......................................................................................................................................... 44

Khanal, G. & Bürkert, A.: “Effect of irrigation and fertilization on biomass yield of cabbage (Brassica

oleracea L. var. capitata) and basil (Ocimum basilicum) in Oman” ........................................................ 45

Meyer, S.; Sundrum, A.; Joergensen, R.G. and Karlovsky, P.: “The emission of nitrous oxide from soil

mixed with cow faeces of different feeding groups” .............................................................................. 46

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Don, A.: “Impact of agricultural industrialization on soil organic carbon stocks in Germany” ............... 47

Session III: Methods in soil organic matter research .................................................................................. 48

Keynote lecture:

Vohland, M.: “VIS-NIR and MIR spectroscopy for soil analysis – possible steps for being more

operational” ............................................................................................................................................ 49

Vormstein, S.; Kaiser, M. and Ludwig, B.: “An incubation experiment to investigate the C-turnover of

beech fine roots of various sizes distributed homogenously or in hot spots in top- and subsoil” ......... 50

Safari, H.; Fricke, T. and Wachendorf, M.: “Sensor data fusion to predict biomass of heterogeneous

pastures” ................................................................................................................................................. 51

Paulus, A.; Hierold, W. and Blasch, G.: “Methods for Predicting Spatial Patterns of Soil Organic Carbon

on Landscape Scale” ................................................................................................................................ 52

Well, R.; Buchen, C.; Lewicka-Szczebak, D.; Giesemann, A. and Flessa, H.: “Using stable isotope

approaches to study nitrogen turnover processes following grassland renewal or conversion to arable

land” ........................................................................................................................................................ 53

Keynote lecture:

Piepho, H.-P.: “Formulating linear mixed models for randomized experiments” .................................. 54

List of Participants ........................................................................................... Error! Bookmark not defined.

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Time Schedule

Wednesday, 11th November 2015

From 9 a.m. Registration

11:00-11:15 Welcome by the speaker of the Research

Training Group

Bernard Ludwig

Session I: Soil organic matter and nutrient dynamics in agriculture

11:15-11:45 Keynote Lecture: Land-management effects on

soil organic matter composition and nutrient

forms

Cornelia Rumpel

11:45-12:00 The Rothamsted carbon model fails to simulate

carbon stock dynamics in high input treatments

of the long-term trial at Puch, Germany

Felix Heitkamp

12:00-12:15 Biotic and abiotic factors controlling carbon

dynamics in subsoil

Juliane Strücker

12:15-12:30 The value of soil organic matter in arable

cropping systems – insights from the

Rothamsted Long-term Experiments

Andy Macdonald

Lunch Break

1:30-1:45 Mitigating infield soil organic carbon erosion – a

landscape scale source or sink of CO2

Peter Fiener

1:45-2:00 Quantitative evidence for soil organic matter

services to agriculture

Christopher Brock

2:00-2:15 Influence of tillage intensity on C and N pools of

different turnover kinetics in surface and

subsurface soils

Michael Kaiser

2:15-2:30 Effects of tillage intensity on the interaction of

soil moisture, temperature and microbial turnover

Sibylle Faust

2:30-2:45 Impact of cutting and fertilization regimes on

SOC and Nt storage in a temperate grassland

soil

Anja Nüsse

2:45-3:00 Efficiency of pasture utilization - Gross and net

pasture productivity of heterogeneous swards

under different grazing intensities

Dorothee Ebeling

Coffee Break

3:30-4:00 Keynote lecture: Effects of elevated CO2 on soil

C and N turnover

Yakov Kuzyakov

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4:00-4:15 Greenhouse gas fluxes and mineral N dynamics

following grassland renewal or conversion to

arable land

Caroline Buchen

4:15-4:30 Cover crop effects on soil fertility and nitrogen

dynamics

Florian Wichern

4:30-4:45 Cover cropping as a mean to close nutrient

cycles in German intensively managed farming

systems

Linda Tendler

4:45-5:00 Priming effects in Israeli soils: impact of treated

wastewater and freshwater irrigation

Marina Anisimova

5:00-6:00 Poster Session in Room H33

6:30-7:30 Guided tours in the tropical green house (Part of the social evening!

7:30 Conference Dinner in the “Zeichensaal” (Part of the social evening!

Thursday, 12th November 2015

Session II: Organic amendments in agriculture

9:00-9:30 Keynote Lecture: Biochar actions in the

environment

Bruno Glaser

9:30-9:45 Biochar stability in agricultural soils during a 19-

month field incubation in Northern Germany,

using natural 13C-abundance

Marco Gronwald

9:45-10:00 Influences of elevated soil temperature and biochar application on different carbon pools of a loess soil

Dennis Grunwald

10:00-10:15 Effects of water restriction on microbial biomass

in goat faeces

Mwanaima

Ramadhan

Coffee Break

10:45-11:00 Effect of irrigation and fertilization on biomass

yield of cabbage (Brassica oleracea L. var.

capitata) and basil (Ocimum basilicum) in Oman

Gunadhish Khanal

11:00-11:15 The emission of nitrous oxide from soil mixed

with cow faeces of different feeding groups

Stephanie Meyer

11:15-11:30 Impact of agricultural industrialization on soil

organic carbon stocks in Germany

Axel Don

11:30-12:00 Open Space – Time for Discussions

Lunch Break

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Session III: Methods in soil organic matter research

1:00-1:30 Keynote Lecture: VIS-NIR and MIR spectroscopy

for soil analysis – possible steps for being more

operational

Michael Vohland

1:30-1:45 An incubation experiment to investigate the C-

turnover of beech fine roots of various sizes

distributed homogenously or in hot spots in top-

and subsoil

Svendja Vormstein

1:45-2:00 Sensor data fusion to predict biomass of

heterogeneous pastures

Hanieh Safari

2:00-2:15 Methods for Predicting Spatial Patterns of Soil

Organic Carbon on Landscape Scale

Anne Paulus

2:15-2:30 Using stable isotope approaches to study

nitrogen turnover processes following grassland

renewal or conversion to arable land

Reinhard Well

Coffee Break

3:15-3:45 Keynote lecture: Formulating linear mixed

models for randomized experiments

Hans-Peter Piepho

3:45-4:00 Closing of the workshop Bernard Ludwig

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Session I: Soil organic matter and nutrient dynamics

in agriculture

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Keynote lecture:

Rumpel, C.: “Land-management effects on soil organic matter composition and nutrient

forms”

Laboratory of Functional Ecology and Ecotoxicology of Agroecosystems, Institute for Ecology

and Environment Paris, Thiverval-Grignon, France

Abstract:

Ecosystem services, such as nutrient availability and carbon storage are linked to soil organic

matter (SOM), which is directly influenced by land management. Agricultural practices such as

fertilization, tillage, and species choice may affect soil organic matter content as well as its

composition. While the consequences of these practices have been studied for SOM quantity,

their effects on SOM composition are less well understood. The aim of this presentation is to

highlight these impacts and their consequences for SOM dynamics and element cycling. I will

focus in particular on temporary grasslands and legacy effects of different grassland

management practices in terms of duration of the grassland phase, fertilization, and species

choice. Duration of the grassland phase, fertilization and species choice affect elemental

coupling and SOM turnover via organic matter input and rhizosphere activity to different extent,

thereby resulting in contrasting SOM storage, microbial C and molecular SOM composition.

Species choice, e.g. high diversity or introduction of legumes, influences element budgets and

soil nutrient availability through plant physiological constraints as well as intra or interspecific

interactions. In conclusion, understanding management impacts on belowground

biogeochemical cycling of elements is necessary in order to fully understand and manage

belowground processes via agricultural practices.

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Macdonald, A.; Powlson, D.; Poulton, P.; Glendining, M.; Whitmore, A.; Watts, C. and

Goulding, K.: “The value of soil organic matter in arable cropping systems – insights

from the Rothamsted Long-term Experiments”

Rothamsted Research, West Common, Harpenden, Hertfordshire, Great Britain.

Abstract:

Agro-ecological research began at Rothamsted in 1843 when the first of the “Classical” field

experiments was established by Lawes and Gilbert. Several of these experiments still continue

and form part of the Rothamsted Long-term Experiments National Capability. The best known

are the Broadbalk Wheat Experiment (started 1843), Hoosfield Spring Barley Experiment

(started 1852) and Park Grass Continuous Hay experiment (started 1856). Other experiments

(some now discontinued) focussed on crop rotations, root crops and legumes. Initial research

focussed on the value of fertilizers and manures for crop production, but, over time, the

experiments have been modified to include the use of lime, herbicides, fungicides, new crop

varieties and larger rates of N to reflect changing agricultural practices. Early experiments with

root crops demonstrated the value of enhanced soil organic matter (SOM) for crop production,

but grain yields of winter wheat on Broadbalk have been surprisingly insensitive to SOM content,

provided sufficient nutrients, particularly N, are applied as inorganic fertilizers. In contrast,

maximum yields of modern spring barley varieties on Hoosfield, well protected from fungal

diseases, are only obtained where SOM content had been increased through long-term

application of manure. There are also, indications that spring sown maize on Broadbalk benefits

from enhanced SOM. In addition, an examination of the plough draught (a measure of soil

strength) on contrasting plots on Broadbalk showed that clay content had the largest influence,

with SOM having the next largest effect. However, even small increases in SOM, from

increasing N fertilizer rates, had a disproportionately large influence on plough draught. The

greater returns of crop residues from the larger crops produced as a result of increased N use

has improved soil structure; an example of sustainable intensification perhaps. Results from

these and other experiments will be presented and discussed.

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Heitkamp, F. & Wendland, M.: “The Rothamsted carbon model fails to simulate carbon

stock dynamics in high input treatments of the long-term trial at Puch, Germany”

Georg-August University Göttingen, Landscape Ecology.

Abstract:

Cropland soils may be a sink or source for atmospheric CO2. In general, it is assumed that C-

input into soil and soil organic carbon (SOC) levels are linearly related. This gives rise to

environmental concerns regarding the removal of crop residue. In recent years, however, it has

been shown that residue incorporation increased SOC levels only to small extents. This was

also true for the well designed and documented long-term experiment of Puch, Germany. The

crop rotation is silage maize – winter wheat – winter barley. Five amendments were combined

with N-fertiliser rates. The levels of organic amendments are control (CON), straw was removed;

slurry (SLU), straw was removed; farmyard manure (FYM), straw was removed; straw

incorporation (STR); and straw incorporation combined with slurry application (STSL). Nitrogen

was applied at five levels: no nitrogen (N0); 50 kg ha-1 year-1 (N1); 100 kg kg ha-1 year-1 (N2);

150 kg ha-1 year-1 (N3); and 200 kg ha-1 year-1 (N4). While these treatments resulted in a wide

range of mean annual carbon input (1 - 5 t C ha-1 year-1), carbon stocks were only slightly

affected by the type of amendment, but not by the rate of N-fertiliser. Compared to the starting

value an increase was observed for STSL, whereas FYM and SLU maintained the initial carbon

stocks and STR and CON lost SOC. Stocks of SOC were successfully modelled with the

independently initialised Rothamsted carbon model (RothC 26-3), but only when C-input was

below 2.5 t ha-1 year-1. At higher input rates, mainly caused by straw incorporation, the

relationship between input and stock became asymptotic. This could not be captured by RothC,

even when changing the residue quality parameter drastically. A first attempt to explain this

finding was made with an incubation experiment (see poster by Shahbaz et al.). Incorporating a

priming effect, which was found the lab study, into RothC is promising, but more work on this is

necessary in future studies.

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Strücker, J. & Joergensen, R.G.:“Biotic and abiotic factors controlling carbon dynamics

in subsoil”

University of Kassel, Faculty of Organic Agricultural Sciences, Department of Soil Biology and

Plant Nutrition.

Abstract:

Subsoil is important for soil organic carbon (SOC) storage in terrestrial ecosystems. Currently

different factors are discussed, which control carbon dynamics in subsoil. The main factors

discussed are changes in the microbial community, physical separation of microorganisms and

substrate, lack of readily degradable plant substrate, which enables microorganisms to degrade

recalcitrant SOC, and inhibition of the microbial community due unfavourable gas

concentrations.

The aim of our study was to investigate the importance of these factors in relation to naturally

different SOC contents in subsoil.

Therefore we sampled one Colluvic Cambisol covering the original soil surface of a Chernozem

and one Haplic Luvisol at four different depths. The SOC content in the subsoil of the Cambisol

(12 mg g-1 soil) was four times higher than in the Luvisol (4 mg g-1 soil). In a first step we

conducted a characterisation of physico-chemical and microbial parameters including substrate

use profiles showing distict patterns for sites and depths. This was followed by one laboratory

and one in-field incubation. Within the laboratory incubation experiment we used disturbed

(sieved < 2 mm) and undisturbed samples to test whether mixing of soil results in higher

mineralisation rates. To investigate the influence of fresh substrate amendment 2 % of

amaranthus (Amaranthus hypochondriacus L.) were added to the disturbed samples.

Furthermore we used two different subsoil gas concentrations in our incubation experiment. All

samples types were subjected to all treatments and incubated for 6 months at 22 °C. Pre- and

post-incubation analyses are supposed to show whether the treatments have an influence on the

development of SOC, microbial biomass C and ergosterol as a marker for saprotrophic fungi.

The in-field incubation of soil with maize roots had a duration of 12, 18 or 24 months and was

supposed to give insights in the fate and pathways of fresh substrate in subsoil under field

conditions.

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Fiener, P.: “Mitigating infield soil organic carbon erosion – a landscape scale source or

sink of CO2?”

University Augsburg, Institute of Geography.

Abstract:

There is a lively scientific debate if globally soil redistribution on arable land results in a net

source or sink of CO2. The reasons for the contrasting global estimates are mostly associated

with a lack of appropriate data and the use of very diverse methodological approaches.

However, when scaling down to small landscape units, where different soil management is set

into practice available tools could be used for reasonable local analyses of erosion-induced C

fluxes. The aim of this study is (i) to briefly illustrate the effects of soil redistribution upon soil

organic carbon (SOC) stocks and CO2 effluxes, and (ii) to use the coupled soil erosion and SOC

turnover model SPEROS-C to exemplarily analyse the potential effects of soil conservation

measures upon the erosion-induced C balance in a small catchment. The modelling exercise

indicates a quite complex situation. In case of conventional tillage soil erosion and deposition

lead to an erosion-induced C sink on the catchment scale. The strength of this sink very much

depends on modelled deposition rates of SOC within the fields and in a downslope grassland

area. Moreover, assumptions take regarding the fate of SOC after entering the stream network

are important. Introducing soil conservation measures slowly reduces the modelled C sink

function, but also reduces potentially harmful matter losses into the stream network. Regarding

the landscape scale effect of soil erosion on CO2 effluxes it can be concluded that erosion by

water and tillage may strengthen the C sink function of an arable landscape, especially if C loses

to the stream network are minimized. In this respect tillage erosion is a more effective process

as it only redistributes soil within fields. If soil conservation measures, commonly associated with

reduced tillage, are introduced the erosion-induced C sink function will slowly fade out, as SOC

at beforehand eroded areas will be slowly recovered and reach a new equilibrium.

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Brock, C. & Naseem, A.: “Quantitative evidence for soil organic matter services”

Justus Liebig University, Giessen, Organic Farming

Abstract:

Soil organic matter is regarded as a key factor of soil quality. In a quite actual review, Fageria

(2012) gives an overview of soil functions and services related to soil organic matter. Still, results

on the effect of SOM levels on the productivity of arable soils are –apparently- contradictive. For

example, Oelofse et al. (2015) do not find an effect of SOM on cereal yields in a comprehensive

multi-site data set from Danmark. On the other hand, a positive relation between SOM and yield

levels of non-legume crops could be observed in a meta-analysis of long-term field experiments

(Brock et al. 2011). The different results could originate from the comparatively small effect of

SOM on productivity at site that is covered by assessments of aggregated site data, even if

aggregation is based on soil and climate. Still, as OM management in practice is bound to a site,

we think that site-specific achievable SOM changes must be the basis for an evaluation of SOM

services. Apart from the effect on productivity, other services to agriculture and the society must

be studied, as water regulation and erosion control.

Against this background we compile records of quantitative evidence for soil organic matter

services and synthesize the data in a new meta-analysis. Special attention will be paid to the

question to what extend single SOM services are related to SOM levels or OM supply to soils. At

the workshop, we want to outline the concept of this survey and present some first results.

References

Brock C, Fließbach A, Oberholzer H-R, Schulz F, Wiesinger K, Reinicke F, Koch W, Pallutt B,

Dittmann B, Zimmer J, Hülsbergen K-J, Leithold G (2011): Relation between soil organic matter

and yield levels of nonlegume crops in organic and conventional farming systems. Journal of

Plant Nutrition and Soil Science 174, 568-575.

Fageria N K (2012): Role of Soil Organic Matter in Maintaining Sustainability of Cropping

Systems. Communications in Soil Science and Plant Analysis 43, 2063-2113.

Oelofse M, Markussen B, Knudsen L, Schelded K, Olesen J E, Stoumann Jensen L, Bruun S

(2015): Do soil organic carbon levels affect potential yields and nitrogen use efficiency? An

analysis of winter wheat and spring barley field trials. European Journal of Agronomy 66, 62–73.

16

Kaiser, M.; Piegholdt, C.; Andruschkewitsch, R.; Linsler, D.; Koch, H-J. and Ludwig, B.:

“Influence of tillage intensity on C and N pools of different turnover kinetics in surface

and subsurface soils”

University of Kassel, Department of Environmental Chemistry

Abstract:

Management options such as the intensity of tillage are known to influence the turnover

dynamics of soil organic matter. However, less information is available about the influence of the

tillage intensity on individual soil organic matter pools with different turnover dynamics in surface

as compared with sub-surface soils. This study aimed to analyze the impact of no tillage (NT),

reduced tillage (RT) and conventional tillage (CT) on labile, intermediate and stable carbon (C)

and nitrogen (N) pools in surface and sub-surface soils. We took surface and sub-surface soil

samples from the three tillage systems in three long-term field experiments in Germany. The

labile, intermediate and stable C and N pool sizes were determined by using the combined

application of a decomposition experiment and a physical-chemical separation procedure. For

the surface soils, we found larger stocks of the labile C and N pool under NT and RT (C, 1.7 and

1.3 t ha−1; N, 180 and 160 kg ha−1) than with CT (C, 0.5 t ha−1; N, 60 kg ha−1). In contrast, we

found significantly larger stocks of the labile C pool under CT (2.7 t ha−1) than with NT and RT (2

t ha−1) for the sub-surface soils. The intermediate pool accounted for 75-84% of the soil organic

C and total N stocks. However, the stocks of the intermediate N and C pools were only distinctly

larger for NT than for CT in the surface soils. The stocks of the stable C and N pools were not

affected by the tillage intensity but were positively correlated with the stocks of the clay-size

fraction and oxalate soluble aluminum, indicating a strong influence of site-specific mineral

characteristics on the size of these pools. Our results indicate soil depth-specific variations in the

response of organic matter pools to tillage of different intensity. This means that the potential

benefits of decreasing tillage intensity with respect to soil functions that are closely related to

organic matter dynamics have to be evaluated separately for surface and sub-surface soils.

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Faust, S.; Koch, H.-J. and Joergensen, R.G.: “Effects of tillage intensity on the interaction

of soil moisture, temperature and microbial turnover”

University of Kassel, Department of Soil Biology and Plant Nutrition

Abstract:

On a 20-years old on-farm tillage experiment, reduced tillage (grubber tillage, GRT) revealed

higher stocks of soil organic carbon (SOC) in comparison to mouldboard plough tillage (MBT)

and no tillage (NT) in a depth of 0-40 cm. However, the underlying mechanisms for the higher

SOC accumulation are not fully understood. Therefore, this study aimed to investigate the

effects of tillage intensity on volumetric water content (VWC) and temperature as key

parameters for the microbial turnover, as well as on soil respiration (R) and microbial biomass C

(Cmic). In August 2013, undisturbed soil core samples were collected from four fields located in

southern and eastern Germany, each divided into the above mentioned three treatments. A total

of 48 soil columns (30 cm diam., 20 cm height) were inserted at an experimental site of the

University of Kassel and one maize plant per columns was grown. Data of soil temperature and

VWC in 5 and 15 cm depth, and R were collected weekly over one year. At the end of the

experiment, SOC and Cmic were measured in 0-10 and 10-20 cm depth. In 0-20 cm depth, SOC

stocks were higher in GRT (42.7 t ha-1) and NT (41.2 t ha-1) compared to MBT (34.7 t ha-1).

These differences were especially pronounced in the 0-10 cm layer (GRT: 23.3 t ha-1, NT: 23.0:

t ha-1, MBT: 17.8 t ha-1), where accordingly VWC were higher in NT (34.6 %) and GRT (33.4 %)

compared to MBT (30.8 %). In 5 cm soil depth, temperature was slightly higher in GRT (14.1°C),

and MBT (14.01°C) than in NT (13.84°C). Similarly, R was highest in GRT (65 mg m-2 h-1),

followed by MBT (55.3 mg m-2 h-1) and NT (53.9 mg m-2 h-1). The higher Cmic to SOC ratio in NT

(2.3 %) and GRT (2.0 %) in comparison to MBT (1.9 %) in 0-20 cm, and the lower qCO2 in GRT

(39.9 mg CO2-C g biomass C-1 d-1) and NT (22.2 mg CO2-C g biomass C-1 d-1) compared to MBT

(41.5 mg CO2-C g biomass C-1 d-1) as well as the lower CO2-C to SOC in GRT (19.2%) and NT

(16.5%) compared to MBT (21%) in 0-10 cm indicate a higher substrate use efficiency and a

slower microbial turnover in NT and GRT in comparison to MBT. This partly explains the higher

SOC accumulation in NT and GRT in 0-20 cm.

18

Nüsse, A.M.; Linsler, D.; Reinsch, T.; Loges, R.; Taube, F. and Ludwig, B.: “Impact of

cutting and fertilization regimes on SOC and Nt storage in a temperate grassland soil”

University of Kassel, Department of Environmental Chemistry

Abstract:

Soil organic carbon (SOC) stored in grassland may affect in conjunction with the stored soil

nitrogen (Nt) the fertility and productivity of grassland ecosystems. Storage and turnover of SOC

and Nt under cutted grassland are mainly affected by management intensity. The objective was

to investigate if varying cutting frequency in combination with fertilization and no fertilization has

an impact on SOC and Nt stocks, soil microbial biomass and the distribution and SOC contents

of water-stable aggregate size-classes.

The study site of the Christian Albrechts University, Kiel is located in north-west Germany close

to Kiel. The field was converted in 2004 to grassland and the dominant soil type was a stagnic

Luvisol. The experiment was established in 2004 in a randomized block design with 3 field

replicates and included the following treatments: three cutting cycles (3C) and five cutting cycles

(5C), without and with N fertilization (fertilization: 360 kg N ha-1 year-1 (Calcium ammonium

nitrate)). Soil samples were taken on each of the 4 treatments in three soil depths (0-10 cm, 10-

30 cm and 30-60 cm) in 2014. SOC and Nt stocks, concentration and SOC contents of water-

stable aggregate size classes (> 2000 µm; 1000-2000 µm; 250-1000 µm, 53-250 µm; < 53 µm)

as well as microbial and fungal biomass were determined. The data were analyzed using a two-

factorial ANOVA.

In soil depth 0-10 cm significant higher SOC stocks were detected for 5C (mean ± SD: 25 t ha-1

± 1.8) in comparison to 3C (21 t ha-1 ± 2) as well as for N unfertilized (31 t ha-1 ± 5.8) compared

to N fertilized (22 t ha-1 ± 2.8) treatments. The Nt stocks were also significantly higher for 5C

(2.17 t ha-1 ± 0.13) than for 3C (1.96 t ha-1 ± 0.17) in the top soil layer. In the soil depth 0-10 cm

significant higher amounts of large macro-aggregates (> 2000 µm) were located in 5C (44% ± 7)

in comparison to 3C (33% ± 2), whereas the amount of smaller macro-aggregates (250-1000

µm) was lower in 5C (5C: 30% ± 4; 3C: 38% ± 1). Under the 5C regime microbial and fungal

biomass were significant higher (by the factor 1.5) in comparison to the 3C regime in the top soil

layer.

The 5C regime led to an increased SOC and Nt stock in comparison to the 3C regime

presumably because of an increased root biomass which was influenced by a changed plant

species composition. Under the N unfertilized treatments the SOC stocks were higher because

due to fertilization the microbial activity was stimulated which caused a higher mineralization of

SOC. The shift from small to large macro-aggregates under the 5C regime is promoted by roots,

fungal hyphae and microbial excretions. This study shows that a 5C regime caused in

comparison to a 3C regime a higher input of SOC and had positive effects on soil fertility and

SOC sequestration. The conventional N fertilization had slightly negative effects on SOC stocks

after 9 years.

19

Ebeling, D.; Tonn, B. and Isselstein, J: “Efficiency of pasture utilization - Gross and net

pasture productivity of heterogeneous swards under different grazing intensities”

Georg-August-University Göttingen, Institute of Grassland Science, Department of Crop Science

Abstract:

Grazing by large herbivores effects grass swards due to defoliation and trampling as well as

spatial and temporal heterogeneous herbage uptake and excrement positioning. In an extensive

grazing system ‘patch grazing’ leads to formation of stable mosaic structures out of short

(frequently defoliated) and tall (infrequently defoliated) sward patch types. Those patch types

differ in their aboveground biomass growth. Because grazing intensity determines the share of

short and tall patch types on a pasture, it must be assumed that a low-intensive pasture grazed

continuously with different grazing intensities differs in productivity. In a long-term extensive

cattle grazing experiment we examined the influence of grazing intensity (target sward heights in

paddock 6, 12 and 18 cm – moderate, extensive and very extensive) on the gross and net

pasture productivity of continuously grazed swards. We hypothesized that both gross and net

pasture productivity (hypothesis 1) as well as the efficiency of pasture utilization (hypothesis 2) is

reduced as target sward height increases.

20

Keynote lecture:

Kuzyakov, Y: “Effects of elevated CO2 on soil C and N turnover”

Georg-August-University Göttingen, Department of Soil Science of Temperate Ecosystems,

Department of Agricultural Soil Science

Abstract:

n.n.

21

Buchen, C.; Benke, M; Flessa, H.; Gensior, A.; Helfrich, M.; Kayser, M. and Well, R.:

“Greenhouse gas fluxes and mineral N dynamics following grassland renewal or

conversion to arable land”

Thünen-Institute of Climate-Smart Agriculture, Braunschweig

Abstract:

Grassland renovation and grassland conversion to arable land are common agricultural

practices on intensively used grassland sites, in order to eliminate sward and soil disturbances

and establish a closed sward with high-quality grass types. It is known that renovation can cause

a flush of soil organic nitrogen mineralization (N) due to soil disturbance during associated soil

tillage (Davies et al. 2001, Velthof et al. 2010) and decomposition of stubbles and roots from the

old grass sward. But knowledge about enhanced nitrous oxide emissions (N2O) and N losses via

leaching associated with different renovation practices is scarce, although global climate change

mitigation and water protection policies force countries to deal with this problem.

The aim of our study is to assess N2O and nitrate (NO3-) fluxes following different grassland

renovation techniques and conversion of grassland to cropland as well as on non-renovated

continuous grassland. We set up a randomized field block trial near Oldenburg (Lower-Saxony,

Germany), using two different soil types with varying C-contents (Histic Gleysoil and Plaggic

Anthrosol) with the following treatments: renovation through (i) reseeding, (ii) chemical killing

and grass seeding, (iii) chemical killing, sward destruction by rotovating, ploughing and grass

seeding. Reference treatments were (iv) conversion to cropland with maize cultivation and (v)

continuous grassland. N2O fluxes were measured weekly using closed chambers. N-losses via

leaching were quantified by measuring weekly soil mineral N in top soil (0-30 cm) and depth

profiles (0-90 cm) in spring and autumn. To close the N-budget, N uptake, N fertilization and

modelling N leaching based on mineral N and hydrological model data will be applied. To identify

processes of N2O production and consumption, stable isotope analyses of emitted N2O, soil

water and soil NO3- were carried out on selected dates and supported by a 15N tracing

experiment.

References:

Davies, M., K. Smith and A. Vinten (2001). "The mineralisation and fate of nitrogen following

ploughing of grass and grass-clover swards." Biology and Fertility of Soils 33(5): 423-434.

Velthof, G., I. Hoving, J. Dolfing, A. Smit, P. Kuikman and O. Oenema (2010). "Method and

timing of grassland renovation affects herbage yield, nitrate leaching, and nitrous oxide emission

in intensively managed grasslands." Nutrient Cycling in Agroecosystems 86(3): 401-412.

22

Wichern, F., in ‘t Zandt, D.; Arico, A.; Lehnert, D.; Cleven, M.; Kanders, M.J.; Berendonk,

C. and Fritz, C.: “Cover crop effects on soil fertility and nitrogen dynamics”

Rhine-Waal University of Applied Sciences; Faculty of Life Sciences

Abstract:

Groundwater pollution with nitrate is a problem in some regions in Germany, especially at the

lower Rhine, caused by excessive nitrogen (N) use and inefficient N uptake by crops. Therefore,

cover crops (CC) are promoted aiming at immobilization of excess residual N in plants. This N

taken up is often estimated by quantifying N in above-ground (AGB) and root biomass. It is well

known, that the below-ground plant biomass (BGB) also contains rhizodeposits (RD), which

have to be taken into account and contribute on average 10-15% to total plant N in legumes and

cereals. Moreover, root architecture affects N uptake and on the other hand is influenced by N

availability. In return, roots also affect soil microorganisms. In a series of experiments, BGB-N of

selected CC was quantified and the effects of N fertilization on root distribution and soil microbial

properties were assessed. In a pot experiment different CC were leaf-labelled by multiple 15N-

urea application. The 15N/14N ratio of plant and soil was measured to calculate total N derived

from RD. In addition, a pot experiment and field experiments with different CC grown at different

fertilizer levels (0, 40, 80 kg N ha-1) were conducted. Plants were separated into AGB and roots

after harvest. Soil samples were analysed for soil microbial biomass carbon (C) and N. The

results show, that 10-15% of the total assimilated N was present as RD. Compared to the pot

experiment, the root-to-shoot ratio was higher in the field, which consequently yielded a larger

contribution of RD to residual N under field conditions. Fertilization had no consistent effect on

the root-to-shoot ratio. Microbial C was not consistently affected by CC presence or fertilization.

However, microbial N was increased by CC independent of fertilization status, indicating

increased N immobilization by soil microorganisms when CC are present. Consequently, CC

store more N than previously assumed and stimulate N immobilization by soil microorganisms.

23

Tendler, L.: “Cover cropping as a mean to close nutrient cycles in German intensively

manged farming systems”

Ingenieurbüro für Ökologie und Landwirtschaft (IfÖL), Kassel

Abstract:

The cultivation of ccs (cc) is currently gaining importance on German arable land. One major

driver ist the CAP green payment which links area-based subsidies to a more environmentally

sound production, this includes, e.g. the cultivation of cc mixtures during winter. Furthermore, it

is beyond debate that ccs are a viable mean to ameliorate soil fertility by e.g. preventing

nutrients from being leached over winter and providing an additional source of organic matter

being added to the soil. However, in agricultural practice the adoption of growing ccs is still

limited. Besides, reliable, region-specific numbers which quantify cc services are rare.

In the frame of the Water Framework Directive various Hessian districts have been identified to

receive intensive consultation aiming at improving groundwater quality. In this concept, the

cultivation of winter ccs is a very effective tool to lower the contents of mineral nitrogen (Nmin) in

the soil before winter by scavenging the surplus nutrients in their biomass.

In the years 2013 and 2014 about 100 cc demonstration trials have been established in more

than 20 different Hessian districts. All of them were run by farmers in the respective regions and

technically supervised by the Engineering Consultant for Environment and Agriculture (I-fÖL) in

Kassel. Thus, the implementation of the cc had to be tailored to the conditions given by the

individual farm‘s environment. Data gathered consists of soil and plant samples (e.g. N-contents

within the subsurface cc biomass before winter, Nmin in the soil).

The accumulated results were analysed by linking site conditions, climate and management

factors to cc performance.

The results retrieved provide information of how much N can be captured with the help of ccs

and which factors are the main drivers leading to a successful, an also economically viable,

implementation. This information can contribute to close nutrient cycles in often very intensively

managed agricultural systems.

24

Anisimova, M.; Heinze, S.; Chen, Y.; Tarchitzky, J. and Marschner, B.: “Priming effects in

Israeli soils: impacts of treated wastewater and freshwater irrigation.”

Ruhr-University Bochum, Institute of Geography, Soil Science/Soil Ecology

Abstract:

Changes in the natural turnover of soil organic matter (SOC) under anthropogenic influences

can lead to the degradation of humic horizons. We investigated the effects of irrigation with

treated waste water (TWW) relative to those of irrigation with freshwater (FW) on the microbial

parameters in soils with different clay content (7 and 13%) in a lysimeter experiment in Israel

with the aim to (i) determine the impact of water quality on soil microbial parameters such as soil

respiration and enzymatic activity, and consequential (ii) work out the changes in the turnover of

soil organic matter (PE, priming effects). Samples were taken from three soil depths (0-10, 10-

20, and 40-60 cm). Soil respiration and PE were determined in a 21-days incubation experiment

after addition of uniformly 14C-labeled fructose. Activity of 10 extracellular enzymes (EEA, from

C-, N-, P-, and S-cycle), phenol oxidase and peroxidase activity (PO+PE), and dehydrogenase

activity (DHA) were assayed. Microbial Community-Level Physiological Profiles (CLPP) using of

four substrates, and microbial biomass were determined. The dominant role of clay content was

observed in the case of priming effects. Only positive priming effects were detected. The

significant highest values were noted in the soil with medium clay content for both irrigation

types in the depth of 40-60 cm: 48% for TWW and 65% for FW. In contrast, in low clay soil the

highest SOC mineralization was observed in the topsoil (0-10 cm): 32% and 56% under the

TWW and FW irrigation, respectively. Generally, both low and medium clayey soils under FW

irrigation were predominantly characterized by significantly highest PE.

25

Postersession Room: H33 (Steinstraße 19, Office and lecture building, 2. floor)

26

P1 Inger Struck: “No-till maize as an alternative sowing practice to conventional

ploughing. Effects on GHG-emissions“

Struck, I.; Reinsch, T.; Loges, R.; Herrmann, A. and Taube, F.

University of Kiel, Institute of Crop Science and Plant Breeding, Grass and Forage Science/Organic Agriculture

Abstract: Silage maize is the primary energy source for intensive dairy and energy production via biogas. Consequently, to comply with the increasing demand, cropping area to cultivate maize has grown steadily, but was often accompanied by land use changes to the disadvantage of permanent grasslands. A conversion of grassland generally implies significant changes in soil carbon and nitrogen stocks, favoring greenhouse gas (GHG) emissions. A reduction of the involved negative environmental impacts is desirable to reduce greenhouse gas emissions while realizing high yields at the same time. The aim of this two-year field experiment was to identify whether cultivation of silage maize as a no-till sowing practice is beneficial in terms of yield related GHG-emissions compared to the conventional silage maize after soil cultivation by plough. For this purpose, a ten year old permanent grassland, arranged in a split-plot-design, was herbicide killed (glyphosate), followed by both ploughing and seeding or direct seeding of the maize plots in end-April. GHG emissions, as in net ecosystem exchange of CO2, as well as N2O and CH4 fluxes from no-till and ploughed maize will be compared to a control variant of 4 cut clover-grass. Furthermore continuous growth sampling for both above- and below-ground biomass production are being realized throughout the whole year. Additional nutrients losses are being quantified with suction cups for leaching losses to the groundwater during winter.

27

P2 Amanda Araujo de França: “Interaction of soil and organic fertilizer enriched with 15 N

an overview“

Araujo de França, A. & Schmidhalter, U.

Technische Universität München, Department of Plant Sciences

Abstract: The biogas boom in Germany not only allows the production of green energy from renewable resources and agricultural waste, but also results in large amount of residues. Its use in farming as organic fertilizer can be an attractive way of enabling the recovery of valuable nutrient elements. A field study is being conducted to evaluate the dynamics of N from biogas residue in spring wheat and eight selected soils from different backgrounds. To this end, the waste is labeled with 15N, in order that the source of N can be identified using mass spectrometry. We expect to estimate the N uptake by the plants from the soil pool and from the organic fertilizer in our experimental conditions. Moreover, we hope to contribute to the insight of soil organic matter transformations after using biogas residue as fertilizer, through the use of spectroscopic techniques such as NMR and EPR. Thus, we could increase knowledge for the efficient use of this waste in agriculture.

28

P3 Friederike Gnädinger: “Challenges in phenotyping maize: How to detect nitrogen use

efficiency of different maize cultivars“

Gnädinger, F. & Schmidhalter, U.

Technische Universität München, Department of Plant Sciences

Abstract: The application of mineral nitrogen fertilizers is probably the most important input factor to achieve high yields (biomass and grain). High N-input farming associated with low nitrogen use efficiency (NUE) may lead to enhanced N-losses affecting the environment, whereas low input farming systems rely strongly on the soil fertility and lead in the long run to nutrient depletion. How do maize plants react to the nitrogen supply and which factors distinguish the performance of maize plants to produce high yield? To which degree is the nitrogen allocation between sink and source genetically or environmentally determined (e.g. nitrogen or drought stress)? Does a differentiated nitrogen supply affect specific traits in maize? Can the detection of plant biomass allocation and plant architecture contribute to an improved understanding of the plant adaptation to environmental factors as well as of the nitrogen use efficiency of a genetically diverse set of maize plants. The challenge therefore is to elucidate the stress adaptation of maize plants depending on genetic or environmental factors with non-destructive high-throughput sensing and digital imaging to improve and shorten tedious selection processes and to further improve nitrogen fertilization in an effective and sustainable way.

29

P4 Muhammad Shahbaz: “High rate of residue addition decreases C stabilization

efficiency due to priming and low physical protection“

Shahbaz, M.; Kuzyakov, Y. and Heitkamp, F.

Georg-August-University Göttingen, Department of Soil Science of Temperate Ecosystems / Physical Geography

Abstract: Increasing crop residue input was suggested as a way to increase soil organic carbon (SOC) levels in cropland soils. Recent work, however, has shown the assumption of SOC models that C-input and SOC-stock are linearly related is not always met. Consequently, adding higher amounts of residue may be ineffective to increase SOC and an alternative use of residues may be justified. The objective was to test under controlled conditions, if the rate and plant part (above- or below-ground) affects mineralization of residues or SOC by interaction with aggregate formation. Labeled wheat residues (leaves, stalks, roots) were added to samples of a loess soil at rates of 1.4 g kg-1 and 5.04 g kg-1. Water content was adjusted to 70% of water holding capacity and CO2-evolution was monitored by means of NaOH traps. Residue- and soil-derived CO2 was determined with an isotopic mixing model using the 13C signature of residues and CO2 of the unamended control. Water-stable aggregates were determined by wet sieving and macro (> 250 µm) - and microaggregates (53-250 µm) were quantified. Soil-derived CO2 doubled in treatments receiving high rates of residues, thus priming on SOC mineralization was lower at low rates. Although macro-aggregate formation was higher at high rate, a higher proportion of initial residues C was retained within macro-aggregates at low rate. At low rate, amendment with roots increased residue-C in microaggregates as compared to leave and stalk amendments. Adding residues at high inputs level reduced the efficiency of different aggregate fractions to retain residue-C and increased CO2-C production by enhancing the mineralization of SOC. At low rate, roots were preferentially retained in stable micro-aggregates. Therefore, there might be an optimal residue-rate at field level above which SOC storage becomes ineffective and alternative use is not on cost of decreasing SOC stocks. However, physical soil fertility should not be disregarded in this respect.

30

P5 Thorsten Scheile: “Influence of excreta patches on biomass growth and selectivity of

grazing animals in low-input pastures“

Scheile, T; Tonn, B. and Isselstein, J.

University of Göttingen, Institute of grassland science

Abstract: In pastures grazed by herbivores a large amount of growing biomass is taken up by the animals, but only a small amount of the biomass is returned via litter. Therefore the influence of the grazing animal on nutrient cycling and productivity especially by the deposition of urine and dung is huge. In the presented work a two-factorial experiment on rotationally grazed pastures was used with the animal species cattle and sheep, as well as the sward types grass-dominated and diverse, to mark urine, dung and control patches in situ on every plot in spring of 2014. These patches were fenced to enable a further feeding of grazing animals within the fenced areas but preventing further contamination by excrements. In the following rotation previously defined transects were used to measure the biomass height of the patches using a sward stick. The height was measured before and after the animals were put onto the plots. This experiment will give further information on feeding behavior, selectivity of the animals at the excreta patches, as well as on the intermediate effect on growing biomass. Excreta patches have a small-scale effect on growing biomass and the feeding behavior in the direct surrounding of the patch. It is expected that the two animal species will differ in their reaction to the excreta patches.

31

P6 Dora Neina: “Estimating mineralizable N of organic materials in tantalite mine soils“

Neina, D.; Buerkert, A. and Joergensen, R.G.

University of Kassel, Organic Plant Production and Agroecosystems Research in the Tropics and Subtropics

Abstract: Nitrogen (N) remains a limiting soil nutrient in the topics particularly in mine soils. Our aim was to assess mineralizable N of goat manure and Canavalia brasiliensis in tantalite mine soils of western Rwanda in a short term leaching incubation experiment. Study soils comprised a native forest, tantalite mine soils restored to pine and eucalyptus forests, arable land and two Technosols with five field replicates each comprising three treatments including: (1) non-amended soil, (2) canavalia, and (3) goat manure. Pre-incubated fresh soils were mixed with acid-washed quartz sand (1:1) and amended with 0.5 mg N g-1 dry soil. The samples were packed into 100 ml PE syringes lined with glass wool and sand at the bottom and pre-leached to remove existing mineral nitrogen before incubation at 22oC. Mineralized N was leached with 200 ml 0.01 M CaCl2 fortnightly using a vacuum pump. The leachates were analyzed for NO3- and NH4+. In the first two weeks of incubation, canavalia mineralized N slightly in the Technosols and arable soil, but immobilized N in forest soils which was intense in the native forest soil. Conversely, goat manure immobilized N in all the soils except native forest soil. Cumulative net N mineralization of canavalia in Technosols and arable soil constituted 306-672% in respect of non-amended soil compared to 18 and 157% in pine and eucalyptus forest soils respectively. Conversely, goat manure treatment formed two groups of high and low N immobilization in Technosols and arable soil, and forest soils respectively. Consequently, mineralizable N of canavalia was highest in Kavumu Technosol constituting 128 µg g-1 soil (p < 0.05) while native forest had -17 µg g-1 soil. Mineralizable N in goat manure treatment negative in all soils except native forest soil ranging from -38.5 to -12 µg g-1 soil. Canavalia therefore has a high potential to supply N in the arable soils and Technosols and may have multiple effects on the soils if co-applied with goat manure.

32

P7 Alberto Andrino de la Fuente: “Solanum lycoperisicum L. carbon investment on

Rizophagus irregularis under different accessible P sources“

Andrino de la Fuente, A.; Schneider, C.; Boy, J. and Guggenberger, Georg

Leibniz University of Hannover, Institute of Soil Science

Abstract: The present work focuses on the control that Solanum lycopersicum L. establishes on photosynthetic carbon transfer to Rizophagus irregularis, an arbuscular mycorrhizal fungi (AMF) under different nutritional scenarios. We hypothesize that the carbon flow, i.e. the carbon investment, of the plant to its fungal symbionts depends on the availability of the nutrient. For that a mesocosm (MC) experiment has been carried out under controlled environmental conditions. The MC consists of a central compartment which contains the mycorrhizal plant connected to a chamber where only the mycelium is able to develop and access to the different nutrient sources. We selected different forms of P (phosphate solution; apatite as P mineral source; and phytate as organic P source). The study has been designed as a time course experiment. In each time point we determined the nutrient content from the whole plant and the cultivation substrate (quartz sand fertilized with a nutrient solution without P), in order to follow the P of the AMF depending on the different nutrient source accessibility. Along the time course experiment, we also determined the CO2 efflux rates coming from the fungi compartment using a non-dispersive infrared gas analyzer as a measure of the heterotrophic activity of the fungi.

Figure 1. A. Cumulative CO2 (mmol). B. Cumulative P gained (mg/plant). Our first results show that there has been a significant carbon investment of the plant to the fungi, measured as CO2 efflux (Figure 1A), being particularly high in those treatments that contain least accessible nutrient source as apatite or phytate. Also it has been seen that all the mycorrhizal plants grown with the different P sources were able to gain same amount of P but with different kinetics along the experiment (Figure 1B). These preliminary results should help us to understand how the performance of nutrient acquisition by the AMF controls the carbon flux below-ground.

33

P8 Paulo Trazzi: “Different particle sizes and amounts of pinus chip biochar in Pinus

teada L. initial growth“

Trazzi, P.; Higa, A.; Kwapinski, W. and Leahy, J.J.

University of Limerick. Chemical and Environmental Sciences, Ireland

Abstract: The aim of this study was to evaluate the use of biochar in different amounts and particle size, as soil conditioner to P. taeda. The biochar used in the treatments was produced by a handmade oven from forest harvesting residues of Pinus sp. chips, and its use was evaluated in two experiments: in the nursery and in the field. In nursery, biochar was sieved in different particle size fractions, creating four different treatments: 0-2 mm; 2 - 15 mm; 15-25 mm 25 - 40 mm, mixed with the soil in three different doses, equivalent to 3, 6 and 12 t ha-1 and used as substrate in 8 dm3 pots. In the field experiment, seven treatments, five by application of increasing amounts of biochar in soil were installed: 2, 4, 6, 8 and 10 t ha-1 (T2, T4, T6, T8 e T10, respectively), and two control treatments, without biochar addition in the soil (T0) and with the application of NPK (2-18-18), also without biochar (TNPK). After 12 months, the results showed that biochar contributed to increase pH, decrease the levels of Al and exchangeable acidity and Al saturation, increase the availability of Ca, Mg, K and P and increase levels of base saturation and sum of bases, as a substrate at forest nursery. There were no significant influence of the particle size evaluated and amount applied in the substrate to P. taeda growth of in the pot experiment. Increasing amounts of biochar resulted in higher recalcitrance of soils. The amount of biochar was more correlated with the soil chemical quality than particle size, after 12 months of evaluation in the forest nursery experiment. In the field, the results obtained 30 months after biochar application showed that biochar improved the soil properties, especially concerning the pH, exchangeable acidity, base saturation, and K and P. After 30 months of biochar application, the volumetric growth of P. taeda trees was positively affected (p=0,18) by the use of biochar as a soil conditioner.

34

P9 M. Hossininia: “Response of saline calcareous soil to gypsum and sulfuric acid

application“

Hossininia, M; Hassan pour, F.; Naghavi, H.; Abbasi, F. and Bastani, Sh.

University of Zabol, Faculty of soil and water, Zabol, Iran

Abstract: Soil salinity is the major causes of soil degradation especially in arid and semiarid regions. In Kerman, southeastern province of Iran, agricultural production and productivity is highly impaired by different level of soils salinity. A laboratory experiment was conducted in soil columns to investigate the effect of different amendments on reclamation of saline calcareous soil (CaCO3 = 20.85%, EC= 10 dS m-1). The soil amendments were comprised of irrigation water (control), gypsum (29.58 ton ha-1) and sulfuric acid (17.75 ton ha-1) application. Leaching was done intermittently and 2.4 pore volumes (PVs) were allowed to pass through the soil columns. Results showed that the concentration of monovalent and bivalent cations as well as EC did not

differ significantly (∝= 0.01) among soil amendments and irrigation water. About 60% of Na+ and 70% of Mg2+ were removed up to 1.5 PV of the soil displaced by drainage water. The cumulative leached Ca2+caused by 2.4 PVs was very small, accounted for about 5 percentage of total content of Ca2+. The concentration of soluble salt in the effluent increased gradually with increased application of leaching water up to 1.5 PV and then approached to an equilibrium concentration. 1.5 PV of water, equivalent to 90 cm of water depth, is required to removed 70% of the soluble salts from 100 cm of soil depth. Irrigation water treatment efficiently decreased the concentration of sodium and magnesium, soil EC and cost, thus, using irrigation water up to 1.5 PV, without application of amendments, is recommended for reclaiming the studied soil.

35

P10 Callum Benfield: “Determination of microbial community structure in subsoil

biopores of different genesis by PLFA and amino sugar analyses“

Benfield, C.; Dippold, M.; Pausch, J. and Kuzyakov, Y.

Georg-August-University of Göttingen, Department of Soil Science of Temperate Ecosystems

Abstract: Biopores are a key factor for root growth and nutrient acquisition from subsoils. How do microbial communities differ between old root pores, earthworm pores and mixed pores? From two soil depths (45–75 cm; 75–105 cm), phospholipids were extracted from samples of three pore types and were derivatised to fatty acid methyl esters. Amino sugar (AS) samples were hydrolysed in 6 M HCl for 8 h at 105°C. Purified samples were derivatised to aldononitrile acetates. Total PLFA * g-1 SOC was higher in pores (45-75 cm) with earthworm activity compared to old root pores and was lowest in bulk soil. The total amount of PLFA * g-1 SOC differed slightly between the two horizons. Gram negative bacteria (G-) were the most abundant group and showed enrichment in earthworm and mixed pores (45-75 cm), likely due to SOM input by earthworms. Gram positive bacteria (G+) were enriched in root pores and bulk soil, i.e. low SOM input compartments, which is indicative for general decomposers of old SOM. A similar pattern was observed for actinobacteria, i.e. consumers of old complex SOM. Fungi displayed a more complex pattern with higher amounts in mixed pores than in root pores, and a community shift. This shift to a higher bacterial contribution in the 75–105 cm horizon was also observed in the AS data. The ratios of glucosamine and galactosamine to muramic acid were smaller in the 75–105 cm horizon in all pores compared to 45–75 cm. Muramic acid contents were not different between pore types. Old root pores attracted old SOM decomposers as G+ bacteria and actinobacteria, whereas pores with earthworm activity and recent SOM input attracted G- bacteria and higher total amounts of PLFA * g-1 SOC, which is linked to improved nutrient turnover. PLFA analysis was a valuable tool to characterise biopores and their microbial ecology. AS are more useful as indicators of microbial necro- than biomass. The lifetime of the pores may have not been long enough to change the AS composition significantly.

36

P11 Marina Anisimova: “Enzymatic activity in urban soils affected by anthropogenic

influences on the example of Rostov agglomeration“

Anisimova M.; Gorbov S.; Bezuglova O.; Marschner B. and Giro N.

Ruhr-Universitaet Bochum, Institute of Geography, Soil Science/Soil Ecology, Germany

Abstract:

Chernozemic soils are characterized by a high accumulation of soil organic carbon and high

microbial activity. However, the native processes of soil organic matter (SOM) transformation

and particularly soil enzymatic activity could be significantly influenced by anthropogenic factors.

The objectives of our study were to determine the impact of different anthropogenic influence on

soil enzymatic activity in urban soils of Rostov agglomeration (South part of Russia). Soil

samples were taken from five soil types: city urbostratozem and greensward (specially

engineered soil) replantozem (Technosols by WRB); city park chernozem situated on the slope

and on the hill, and chernozem of abandoned field to the depths of 130-170 cm (Calcic

Chernozems by WRB). Activity of 9 extracellular enzymes (EEA, from C-, N-, P-, and S-cycle),

phenol oxidase and peroxidase activity (PO+PE) were assayed. The results showed no clear

correlation between PO+PE and SOM; deepest horizons of three soil profiles with the lowest

SOM content were characterized by significantly high PO+PE. The specially engineered

greensward soil showed constantly high PO to the depth of 110 cm. The city park chernozem

with the highest soil organic carbon content situated on the hill showed a very high EEA of C-

cycle presented for the most part by α-glucosidase. The total EEA in the city urbostratozem and

the greensward replantozem was about 80% lower in comparison to the EEA of the city park and

abandoned field soils. The abandoned field chernozem demonstrated also a more even

distribution of EEA in profile. Generally it can be concluded that enzymatic activity and enzymes

distribution in chernozemic soils affected by different anthropogenic factors (use) can strong

differ from those of native soils and give some concrete evidences about the processes of soil

organic matter transformation.

37

P12 Ulf Schneidewind: “Indicators for carbon cycling in organic or conventionally

managed cocoa production systems in Alto Beni, Bolivia“

Schneidewind, U.; Hackmann, F.; Niether, W.; Schneider, M.; Gerold, G. and Heitkamp, F.

Georg-August-University of Göttingen, Landscape Ecology

Abstract: Carbon loss by deforestation and inadequate soil management can potentially be decreased by locally adapted agroforestry (AF) systems. The potential of carbon sequestration of cocoa farming systems depend on soil and climate conditions as well as management, structure, and the age of the plantation. Cocoa AF systems with various shade trees, shrubs and herbaceous plant species offer an opportunity to increase and sequester organic carbon in tropical agroecosystems by higher aboveground and below-ground biomass in comparison to monoculture. The Research Institute of Organic Agriculture (FiBL) and local partners established a long term field trial with different systems (agroforestry vs. full sun) and management (organic vs. conventional, see poster by Niether et al.).The objective of the study is to quantify (1) above- and belowground biomass, (2) carbon, nitrogen, and phosphorous in microbial biomass as indicators of soil fertility and (3) litter decomposition, which may be affected by litter chemistry or microclimate. Aboveground biomass was highest in AF systems due to the presence of shade trees with a tendency of faster growth in conventionally managed systems. Microbial biomass C and N contents were mainly affected in the uppermost layers with lowest values in the conventional full sun system. In vicinity to legume trees, however, microbial C and especially N contents were increased down into the B-horizon. Litter decomposition in the field was remarkably similar after one year duration. Cocoa litter decomposed slower than legume-tree litter. Overall, results indicate a faster C-sequestration in biomass in conventional systems, which however, may level out with maturity of the systems. Microbial indices showed that negative effects of full sun monoculture can be reduced by either organic management or by switching to agroforestry. Nutrient recycling from cocoa leaves was similar in all systems, but introduction of legume trees provide easily degradable leaves.

38

P13 Wiebke Niether: “Organic cocoa production: a sustainable alternative?“

Niether, W.; Schneidewind, U; Schneider, M.; Gerold, G. and Heitkamp, F.

Georg-August-University of Göttingen, Landscape Ecology

Abstract: Organic agriculture is supposed to be a sustainable form of land-use. However, yields are often lower than in conventional agriculture, which shed some doubt on the sustainability of organic agriculture. In humid regions of the tropics, however, organic agriculture has potential for high yields in the long-term. Unfortunately, there is little information on the performance of perennial cultures, such as cocoa, which can also be grown in diverse agroforestry (AF) systems. Potentially, a higher proportion of carbon in vegetation and soil can be preserved in organically (ORG) managed agroecosystems as compared to conventionally (CONV) managed systems and, due to their structure, more in AF systems than in monoculture (MONO) plantations. This will help to reduce CO2 emissions from land-use. In a long-term trial in the Bolivian lowlands established by the Research Institute of Organic Agriculture (FiBL, Switzerland), we aim to quantify how carbon stocks and nutrient cycling are affected by different systems. The factors “system” (MONO vs. AF) and “management” (ORG vs. CONV) are arranged in a randomized block design (n = 4). On this poster, the design and management is presented, complemented with a differentiation of the stand structure by canopy analysis. Moreover, the effects of the differently managed systems on vertical water fluxes, microclimate and litterfall are shown. Such information is needed to differentiate between processes regulating carbon and nutrient fluxes.

39

Session II: Organic amendments in agriculture

40

Keynote lecture:

Glaser, B.: “Biochar Actions in the Environment”

Martin Luther University Halle-Wittenberg, Soil Biogeochemistry, Institute of Agronomy and

Nutritional Sciences

Abstract:

1. MOTIVATION

Meanwhile, biochar has reached human and animal nutrition. Increasing contradictory scientific

results urgently request a more detailed investigation of mechanisms of how biochar interacts in

the environment. I will summarize current state of the art of theoretical and observed biochar

mechanisms under different ecological aspects.

2. EXPECTED EFFECTS DUE TO PHYSICO-CHEMICAL STRUCTURE OF BIOCHAR

The chemical structure of fresh biochar is characterized by a high proportion of condensed

aromatic moieties and low proportions of functional groups, biologically degradable organic

carbon, and ash. From a physical point of view, biochar is a porous media. The big surface area

is dominated by pores in the nm range, while the plant-available water-holding capacity is

dominated by pores bigger than 20 µm. Ash components can serve as mineral fertilizer for

plants and microorganisms. Labile organic carbon can be assimilated by soil microorganisms,

probably explaining the rapid initial microbial activity and respiration (CO2 emission) after biochar

addition to soil. Condensed aromatic moieties of biochar are much more stable than natural

organic matter and can act as long-term C sink in soil due to its intrinsic chemical recalcitrance.

Interaction of biochar with soil minerals will occur only after partial oxidation and formation of

functional groups such as phenolic or carboxylic groups. Enhanced biological activity especially

during composting will facilitate and promote such reactions.

3. PHYSICAL BIOCHAR INTERACTIONS, ESPECIALLY WITH WATER

Biochar influences many physical soil properties such as primary and secondary structure,

porosity, permeability and density. The chemical structure of biochar is dominated by

hydrophobic poly-condensed aromatic moieties repelling water, while the physical structure of

biochar is dominated by macro and micro pores attracting water. If water is in contact with

biochar, it is attracted by hydrophilic functional groups (phenolic, carboxylic) and by capillary

forces of pores. New scientific evidence provided interactions of water with graphene sheets of

biochar despite their hydrophobic chemical character.

4. CHEMICAL BIOCHAR INTERACTIONS – STABILITY VERSUS REACTIVITY

The stability of biochar was controversially discussed in scientific literature. Potential

explanations for this discrepancy are methodological aspects as well as the variable proportion

of stable poly-condensed aromatic carbon of biochar. A quantification of this poly-condensed

aromatic C is crucial with respect to the C sequestration potential of biochar. On the other hand,

41

reactivity of biochar is crucial for other positive ecosystem functions such as nutrient holding

capacity and formation of stable organo-mineral complexes and / or soil aggregation.

5. BIOTIC BIOCHAR INTERACTIONS WITH PLANTS AND MICROORGANISMS

Soil microbial diversity is a function of soil (especially pH) and site properties (temperature and

precipitation). As biochar can influence those properties, it has also indirect effects on soil

microbial diversity. Therefore, for a proper investigation of direct biochar effects on soil microbial

diversity, these factors need to be kept constant, which is most often not the case. Nevertheless,

direct biochar effects on soil microorganisms has been reported, which can be explained by the

high surface area and the occurrence of easily degradable organic carbon attached to this

surface.

6. TOXICOLOGICAL ASPECTS OF BIOCHAR IN THE ENVIRONMENT

Thermochemical conversion of organic matter involves production of low molecular weight

condensed aromatic moieties also known as polycyclic aromatic hydrocarbons and dioxins.

Hydrothermal carbonization does not produce such compounds due to the relatively low

temperature. On the other hand, hydrothermal carbonization produces a variety of low molecular

organic compounds potentially toxic for plants. Contents of polycyclic aromatic hydrocarbons

and dioxins can be kept low by technical parameters (temperature, separation of biochar and

condensates). Phytotoxic low molecular weight organic compounds of hydrochars can be

eliminated by biological post-production processes such as aerobic composting. Little scientific

literature exists about the biological actions of biochar in men and animals. However, biochar

should act similar to activated charcoal. The only constraint is particle size, which should be

higher than 10 µm to avoid accumulation in lung tissue.

7. SUMMARY AND CONCLUSIONS

From the physico-chemical structure of biochars, a number of biochar reaction mechanism in the

environment can be deduced, especially with respect to stability and physical and chemical

reactivity. More difficult and thus, less certain are biotic interactions with microorganisms, plant,

animal, and men.

42

Gronwald, M.; Vos, C.; Don, A. and Helfrich, M.: “Biochar stability in agricultural soils

during a 19-month field incubation in Northern Germany, using natural 13C-abundance”

Thünen-Institute of Climate-Smart Agriculture, Braunschweig

Abstract:

The incorporation of chars into soil offers a contribution to sequester carbon and to improve

soils’ fertility. Nevertheless, to assess the C storage potential in soil it is necessary to investigate

the stability of chars against degradation. In temperate soils, there are no long-term studies

which compare different types of chars under field conditions systematically.

We examined chars from two different production processes (pyrochar (produced via pyrolysis)

and hydrochar (via hydrothermal carbonization). We chose Miscanthus (C4-plant; δ 13C -12.7‰)

as feedstock material and applied the chars to three agricultural soils (one loamic Cambisol (δ

13C -27.2±0.19‰), one arenic (δ 13C -27.1±0.05‰), as well as one cambic Planosol (δ 13C -

27.4±0.14‰)) that had exclusively been under C3-vegetation. The difference in the natural 13C

abundance between the soils and chars (δ 13C for hydrochar -13.5‰; for pyrochar -14.2‰)

allowed the calculations of char-derived C in the soil at the time of sampling. The chars were

incorporated into the plow horizon to 70 x 70 cm mini-plots in three different arable soils in Lower

Saxony. Randomly distributed soil cores were sampled directly after application (T0), after 7

months (T1) and after 19 months (T2)) and C-stocks as well as the 13C-12C isotope ratios (δ13C)

were analyzed in order to calculate the proportions of char-derived C and determine mean

residence times (MRT) of the applied chars. We fitted a one-pool decay model to estimate the

MRT of chars. In order to correct mixing of soil originally present in the mini plots with soil

incorporated due to ploughing, inert zinc was mixed into the mini plots and its content in the soil

cores was determined for all three sampling dates.

Originally soil remained in plots after dilution were 60±15% (T1) and 30±7% (T2). While C

derived from pyrochar did not change, hydrochars’ C decreased to 75±20% residual C from char

after 19 month in-situ field incubation. We found that hydrochar was less stable in the

investigated soils (MRT=5±1 yrs) compared to pyrochar (MRT=42±10 yrs). But among the

replicates a large variability for all sites was observed for char-derived C during the experimental

time and the corresponding MRT.

However, the experimental time was too short to estimate MRTs which gained a high error

because labile C-pools were under and stabile C-pools were overestimated. This field trial

provides information on the possible use of pyrochar instead of hydrochar as stable carbon

storage in soil under common agricultural practices. Furthermore, faster degradation of

hydrochar compared to pyrochar showed their potential as a long-term fertilizer through slow

nutrient release into soils. But real long-term studies are necessary to gain more information

about char stability in soils.

43

Grunwald, D.; Kaiser, M.; Bamminger, C.; Poll, C; Marhan, S. and Ludwig, B.: “Influences

of elevated soil temperature and biochar application on different carbon pools of a loess

soil”

University of Kassel, Department of Environmental Chemistry

Abstract:

Potential climate change-related increase in soil temperatures might lead to intensified soil

organic matter (SOM) decomposition and larger emissions of CO2. On the other hand, the

application of biochar to arable soils is regarded as a management option to increase and

stabilize the SOM content. SOM fractions differing in their mean residence time and thus

importance for long term carbon storage can be experimentally isolated. SOM in aggregate-size

fractions is for example characterized by longer turnover times with decreasing size. To date, the

influence of biochar on such fractions in dependence of soil temperature is largely unclear. The

objective of this study was to analyze the effect of biochar application and elevated soil

temperatures on the size and composition of different carbon pools, as shown by experimentally

separated SOM fractions, the microbial biomass carbon and CO2 emission as basal respiration

rates.

Four field replicates of four treatments of the Hohenheim Climate Change experiment,

established on a loess soil, were sampled in the depths of 0-5 and 5-15 cm: ambient or elevated

soil temperature (+ 2.5 °C, for six years before sampling) and with or without Miscanthus biochar

(700 °C) application of 30 t ha-1 one year before sampling. Samples were incubated at 20 °C for

14 days to determine basal respiration rates and subsequently total C and 13C in the microbial

biomass to trace the carbon originating from the biochar. Aggregate size-fractions were

separated by wet-sieving and analyzed for total C and 13C content. A density fractionation

separating the free and occluded light fractions from the heavy fraction and a subsequent

spectroscopic analysis of all fractions are in progress. The resulting data for each soil depth

were analyzed with a two-way analysis of variance and subsequent unpaired t-tests for equal

variances in case of a significant interaction.

Independent of soil temperature and depth, samples with biochar showed significantly (p < 0.05)

larger basal respiration rates. Elevated temperatures significantly increased microbial C in 5 – 15

cm depth, while in 0 – 5 cm significant increases by biochar and elevated temperature were

found. No incorporation of biochar-C into the microbial biomass was found. Also, no effects of

biochar or temperature on the carbon associated with the different aggregate size-fractions were

observed. However, 1 – 19 % of the total biochar-C was found in the different aggregate

fractions. We expect to find a similar incorporation of biochar into the occluded light fraction and

more distinct differences between the different fractions regarding the composition of the

associated SOM by the following spectroscopic analyses.

44

Ramadhan, M. R.; Joergensen, R.G and Schlecht, E.: “Effects of water restriction on

microbial biomass in goat faeces”

University of Kassel, Department of Animal Husbandry in the Tropics and Sub-tropics

Abstract:

Over the past five decades, water restriction in ruminants has been widely studied with the main

focus being to evaluate and understand the physiological basis that enable ruminants to tolerate

water shortage. In addition, more studies have dwelt on the effects of water restriction on feed

intake and utilization. However, despite the aforesaid extensive research, information

considering the effect of water restriction on faecal composition is largely unexplored. Much less

is known about the effect of water intake on the microbes present in ruminant faeces. Thus, the

aim of this study was to determine the effect of water restriction on microbial biomass in goat

faeces in order to better understand the microbial turnover evoked by water restriction. Two

experimental trials of 3 months each were carried out in the years 2013 and 2014 in Sultan

Qaboos University, Oman. These trials were set up as a complete Latin Square design whereby,

ten adult male goats were subjected to three water treatments: 1) water ad libitum (control); 2)

water restricted at approximately 85% of individual ad libitum consumption; 3) water restricted at

approximately 70% of individual ad libitum consumption. Each of the two trials entailed three

periods, each comprising of 16 days of adaptation and 8 days of sampling. Rhodes grass hay

and barley were given as feed at 1.3 above maintenance with a ratio of 1:1. About 30 g of fresh

faeces were collected one hour after morning feeding and immediately frozen at -20 °C. The

faecal samples were then freeze-dried before the microbial analysis. For the determination of

bacterial and fungal biomass, amino sugars and ergosterol methods were employed. The mixed

model procedure in SAS was used to conduct an ANOVA with year, period and treatment as

fixed effects. Bacterial C and muramic acid were significantly reduced (p<0.05) in 70% water

treatment in 2014. Water restriction had no effect on faecal concentrations of ergosterol, fungal

C, mannosamine, galactosamine and glucosamine in both years. Although the faecal

concentrations of microbial C were not statistically different (p<0.05), the mean values were

seen to be higher in the 100% water treatment compared to the 70% treatment in 2014. Water

restriction did not affect the faecal fungal biomass but decreased the bacterial biomass.

45

Khanal, G. & Bürkert, A.: “Effect of irrigation and fertilization on biomass yield of cabbage

(Brassica oleracea L. var. capitata) and basil (Ocimum basilicum) in Oman”

University of Kassel, Department of Organic Plant Production and Agroecosystems Research in

the Tropics and Subtropics

Abstract:

The increase in agricultural activities in Oman, especially in the Al-Batina region, is a concern

because of the sparse water resources and available low soil organic carbon (SOC). Almost

90% of Oman’s fresh water, mostly the ground water, is used for agricultural purpose and

agricultural actives continue to degrade SOC. Therefore, it is important to optimize water use

and maintain or increase SOC by incorporating more soil organic matter (SOM) for sustainable

agriculture. The objective of this experiment was to investigate the effect of irrigation in

combination with the application of either organic or mineral fertilizers on crop biomass yield and

SOC. The field experiment was setup in a factorial design with three different level of irrigation:

100% flood irrigation, 70% flood irrigation and drip irrigation, and 5 different fertilizer treatments:

goat manure (GM), goat manure & activated charcoal (GM+), compost (CM), compost &

activated charcoal (CM+) and mineral fertilizer (M). Irrigation was regulated with the help of flow

meters, tensiometers, soil moisture sensors and pan evaporation (Epan). Irrigation events were

scheduled according to the requirement of 100% irrigation. Cabbage and basil, were planted in

rotation. Crop biomass was harvested in the years 2013-2014 and 2014-2015, to estimate dry

matter yield. Soil samples were collected at the beginning and at the end of the growing seasons

to determine SOC. All the organic fertilizer treated plots, irrespective of irrigation, performed

poorly in the first season of cabbage crop compared to significantly higher yielding M fertilizer

treated plots which yielded 6.2-8.5 ton ha-1. Biomass yield of basil crops were also lower in the

first season irrespective of the treatment. Drip irrigated plots had the lowest yields and 100%

irrigated M plots yielded the maximum with 1.3 ton ha-1. The poor performance of basil crop in

the first year might be attributed to the overall low temperatures during the cropping period. In

the second season, 100% irrigated plots performed better in both crops. In cabbage, 100%

irrigated M plots yielded the highest, 7.3 ton ha-1. This yield was close to 100% irrigated GM and

CM plots, 5.5 and 5.6 ton ha-1 respectively. In the second year basil crops, all the 100% irrigated

plots performed better with 100% irrigated GM plots yielding highest 3.3 ton ha-1 and 100%

irrigated M and C both yielding ~3 ton ha-1. While irrigation is still the most important factor in

achieving the higher yields in most of the cases in this experiment, we can say that the using

organic fertilizers high in organic matter such as GM and CM to improve and maintain soil

organic carbon are also possible options.

46

Meyer, S.; Sundrum, A.; Joergensen, R.G. and Karlovsky, P.: “The emission of nitrous

oxide from soil mixed with cow faeces of different feeding groups”

University of Kassel, Department of Animal Nutrition and Animal Health

Abstract:

The feces of dairy cows is the basis of many organic fertilizer. Previous studies have shown that

the chemical and microbiological properties of the feces vary with the feeding regime. On dairy

farms the feeding regime depends on the lactation state of the animal (high-yielding, low-yielding

and non-lactating cows). The fiber-rich, low-protein feed of the non-lactating cows leads to a

fiber-rich feces with lower concentrations of carbon and nitrogen fractions such as easily

available C and N. At the same time the microbial biomass is lower and dominated by fungi.

With the application of organic fertilizers nutrients and microorganisms are added to the soil.

This results in an enhanced emission of greenhouse gases such as nitrous oxide. The extent of

the emission depends on the composition of the fertilizer.

Former experiments have shown a higher emission from soil mixed with feces of non-lactating

cows compared to feces of the other feeding groups. The mechanism behind these different

nitrous oxide emissions is not completely understood.

To obtain information on this matter an incubation experiment was conducted under

standardized conditions. Therefor soil was mixed with feces of the different feeding regimes and

the emission of N2O measured continuously. Additionally, in the course of the experiment sub-

samples of soil were taken to determine the N-mineralization, the microbial biomass, as well as

the (de)nitrifying community by qPCR.

47

Don, A.: “Impact of agricultural industrialization on soil organic carbon stocks in

Germany”

Thünen-Institute of Climate-Smart Agriculture, Braunschweig

Abstract:

Carbon dioxide (CO2) emissions from soils are 10 times higher with around 60 Pg C a-1 than

anthropogenic CO2 emissions from fossil burning. At the same time around 60 Pg carbon is

added to the soils as litter. Thus, the balance between both fluxes is supposed to be close to

zero for a global earth system in steady state without human perturbations. However, the global

carbon flux has been altered by humans since thousands of years by extracting biomass carbon

as food, feed and fiber with global estimate of 24% of net primary productivity. This extracted

carbon fraction is low in forests but high agricultural systems, in particular in croplands. Thus,

cropland carbon stocks are depleted by around 30% as compared to forest soil. The most

common measures to enhance soil carbon stocks relied on reducing the C output from the

system by reducing the decomposition rate with reduced or abandoned tillage. However, this

has been turned up to be ineffective and with small impact on carbon fluxes and stocks. In order

to compensate for the C extraction at croplands, crop residues and external input with organic

amendments play a pivotal role in maintaining cropland´s carbon stocks. In a review study I

followed the historical development of carbon fluxes for German agricultural soils by exploring

the impact of agricultural developments, transitions and industrialization on soil carbon stocks.

Since the 1970s decreasing numbers of dairy animals caused a decline on manure production

by around 30% compared to 2014. Moreover, the dairy production became concentrated in

certain regions leaving around 40% of croplands without any manure input. Also C input with

crop residues was affected by agricultural developments and are closely linked to yields, crop

type, extraction of straw and the use of stalk-reducing substances. The implications of these

developments for soil carbon stocks are discussed.

48

Session III: Methods in soil organic matter research

49

Keynote lecture:

Vohland, M.: “VIS-NIR and MIR spectroscopy for soil analysis – possible steps for being

more operational”

Leipzig University, Geoinformatics and Remote Sensing, Institute for Geography

Abstract:

In the field of soil organic matter research a huge number of studies exist that highlight

rapidness and saving of costs as the main advantages of MIR and especially VIS-NIR

spectroscopy. However, operationality is coupled to a certain level of accuracy, so that a

reduction of the number of wet-chemical analyses is indeed justified. In addition, researchers

often tend to develop local calibration models for each field they measure with spectroscopy,

which might be appropriate to reproduce the local variability of soil properties, but is very

ineffective and far away from being operational for regional approaches.

Three issues of being operational are addressed in this contribution:

(i) Calibration method: A series of strategies exist to optimise multivariate calibrations

from spectral data. For a regional dataset of 172 topsoil samples we applied different

techniques of spectral variable selection (combined with PLSR) and data

transformation. In total, we found that using continuous wavelet transformation for

decomposing the spectra into multiple frequency scale components together with an

efficient variable selection strategy (CARS, “competitive adaptive reweighted

sampling”) allowed the most accurate assessment of soil properties at the regional

scale.

(ii) Spatial coverage: Airborne hyperspectral image data provide a large amount of in-

situ measurements (pixel values) and thus may allow spatial patterns of soil variables

to be reproduced without spatial interpolation. However, data availability and data

quality are still bottlenecks.

(iii) Applicability of calibrated models to new situations: Spectral libraries that cover a

wide range of soil variability may be useful to calibrate models that may allow the

prediction of soil properties in other regions or for other local situations. In this

context, we address the benefits of spiking, which involves the addition of a small

number of samples from the local data to the calibration set to improve prediction

accuracy.

50

Vormstein, S.; Kaiser, M. and Ludwig, B.: “An incubation experiment to investigate the C-

turnover of beech fine roots of various sizes distributed homogenously or in hot spots in

top- and subsoil”

University of Kassel, Department of Environmental Chemistry

Abstract:

Plant roots entering the mineral soil at different depths and their decomposition intensity are an

important contribution for the organic C stored in forest soil. Differences between topsoil and

subsoil regarding the concentration, distribution and particle size of roots might affect the

mineralization kinetics. However, only little is known about the key factors governing the

mineralization kinetics of beech fine roots in topsoils compared to subsoils. The aim of the study

was to analyze the effects of the above mentioned factors on their decomposition rates in sieved

composite samples and intact columns from the top- and subsoil of sandy Cambisol under

beech. An incubation experiment was carried out for 365 days at 10°C and at soil water contents

of 50% of the water-holding capacity to determine the CO2 emission using an automated

microcosm system. The treatments included control soils (homogenized and sieved <2 mm or as

intact soil column) and soil material with applications of beech fine roots varying in size (<2 mm

and 1-2 cm), application rate (2 and 8 g kg-1), distributed homogenously or in form of hot spots.

At the end of the incubation experiment subsamples of the minimally disturbed (hot spots and

the surrounding soil) and homogenized soil columns were taken and analyzed for total C and N,

microbial C and N, ergosterol, macro nutrients and mineral N. First order models were used to

evaluate the cumulative C mineralization data. Calibration of a one-pool model was carried out

for the C mineralization of the control topsoil and of a two-pool model for the C mineralization

data of the treatment with root application to subsoil at the rate of 2 g kg-1. All other treatments

were validated using the three pools obtained in the calibration for the topsoil and the two-pool

model for the subsoils. The CO2 emission rates ranged between 281 and 976 mg CO2-C per kg

soil for the topsoil and between 5 and 676 mg CO2-C per kg soil for the subsoil treatments. The

results indicate that the root distribution does not affect the mineralization kinetics markedly. In

contrast, the C-turnover was markedly affected by the concentration and the size of beech fine

roots. Correlation analyses showed positive correlations between the microbial biomass and the

CO2 emission in the homogenized and the hot spot material and a positive effect of Ca and K in

the hot spots on the microbial biomass and C-turnover.

51

Safari, H.; Fricke, T. and Wachendorf, M.: “Sensor data fusion to predict biomass of

heterogeneous pastures”

University of Kassel, Section Grassland Science and Renewable Energy

Abstract:

Site-specific determination of biomass in pastures is challenging due to spatial and phenological

heterogeneity of swards. This study aimed to evaluate the potential of an ultrasonic and

hyperspectral sensor combination to predict and map spatial distribution patterns of biomass in

heterogeneous pastures. Field measurements were conducted on paddocks under different

grazing intensities in 2013 and 2014 at the experimental farm Relliehausen of Goettingen

University, Germany. Mobile measurements were conducted by mounting ultrasonic and

reflectance sensors in combination with a DGPS on a remotely controlled vehicle. Reference

data were measured and sampled on 0.25 m² subplots to develop calibration models. Ultrasonic

sward heights (USH) were combined with different hyperspectral reflection variables to identify

calibration models of high predictive capability. Best prediction accuracies were achieved by a

combination of USH and date specific band selection of the normalized spectral vegetation index

(NDSI) reaching R² values between 0.63 and 0.92 for the prediction of fresh matter yield. Spatial

distribution maps of biomass were generated with 10 cm ground resolution from the mobile

measurement data by applying the calibration models through ordinary kriging interpolation.

Although species-specific traits affected prediction accuracy, which eventually helps to identify

limits and potentials of the system, the sensor combination was promising for mapping and

analysis of spatio-temporal pasture dynamics, even in heterogeneous swards.

52

Paulus, A.; Hierold, W. and Blasch, G.: “Methods for Predicting Spatial Patterns of Soil

Organic Carbon on Landscape Scale”

Leibniz-Zentrum für Agrarlandschaftsforschung, Müncheberg

Abstract:

Due to the high variability of the spatial distribution of soil organic carbon (SOC), estimating soil

carbon pools is a highly complex issue. Spatial SOC patterns largely depend on landscape-scale

factors such as land use, soil properties, local climate and geology. Hence, landscape features

determine whether soil is a carbon source or sink. We apply data mining, multitemporal soil

pattern analysis and GIS spatial modeling in order to model and predict spatial SOC patterns of

cropland sites in a catchment in Northeast Germany.

The data mining tool Cubist is used for constructing a rule-based stochastic model of topsoil

organic carbon stocks. Environmental covariates of various scales are derived from satellite

imagery, digital elevation models and soil maps.

In a separate step, multitemporal remote sensing images are used for predicting topsoil organic

carbon content in the same study area. The multitemporal approach allows the elimination of

temporal patterns leaving only spatiotemporally stable information on soil attributes. The model

is calibrated to four test fields and subsequently transferred to landscape scale.

Our results show that static patterns of SOC are highly connected to terrain attributes indicating

the importance of erosion and deposition processes for the spatial variability of SOC. Results

also show that both rule-based models and multitemporal soil pattern analysis are suitable

methods for modeling and predicting spatial SOC patterns on landscape scale. This way we are

able to produce high-resolution maps for an area of 200km².

53

Well, R.; Buchen, C.; Lewicka-Szczebak, D.; Giesemann, A. and Flessa, H.: “Using stable

isotope approaches to study nitrogen turnover processes following grassland renewal or

conversion to arable land”

Thünen-Institute of Climate-Smart Agriculture, Braunschweig

Abstract:

Soil N2O fluxes originate from a multiple of mostly microbial processes where the currently

known include production by nitrification (including hydroxylamine oxidation and nitrifier

denitrification), fungal and bacterial denitrification, co-denitrification, DNRA as well as N2O

reduction to N2 by bacterial denitrification. Better knowledge on their significance and control is

needed to better predict gaseous N fluxes from soil. Some potential and limitations of using

stable isotope methods to address the abovementioned processes will be briefly addressed.

In recent years, isotopologue values of N2O such as δ 18O, average δ 15N (δ15Nbulk) and 15N site

preference (SP = difference in δ 15N between the central and peripheral N positions of the

asymmetric N2O molecule) have been used to constrain the atmospheric N2O budget and to

characterize N2O turnover processes including N2O production and reduction by microbial

denitrification. However, the use of this approach to study N2O dynamics in soils requires

knowledge of isotope fractionation factors for the various partial processes involved. Recent

progress on the principles of isotope fractionation modeling to estimate N2O reduction and on

the role of microbial groups and their specific impact on isotopologue values will be presented.

Quantifying dinitrogen and nitrous oxide fluxes from different soil N pools and processes can be

also accomplished using the 15N tracer technique, but this is subject to several sources of bias.

Homogenous labelling is a prerequisite for accurate quantification of process rates but cannot be

perfectly realized. The question is addressed, if and how non-homogeneity of labelling and

microbial activity can be identified, predicted, solved and what it might tell us on process

dynamics.

We used both approaches, i.e. isotopologues of N2O and 15N tracing, to elucidate processes

governing N2O fluxes from grasslands renovation and conversion to arable land. Field studies in

soils with varying C-contents (Histic Gleysoil and Plaggic Anthrosol) were conducted with the

following treatments: (i) grassland renovation through chemical killing, sward destruction by

rotovating, ploughing and grass seeding, (ii) grassland conversion to cropland with maize

cultivation and (iii) continuous grassland. We will report N2 and N2O fluxes, product ratios of

denitrification as indicated by both approaches, and apportionment of N2O fluxes to different

microbial processes based on N2O isotopologues.

54

Keynote lecture:

Piepho, H.-P.: “Formulating linear mixed models for randomized experiments”

Universität Hohenheim, Biostatistics Unit

Abstract:

Designed experiments conducted by crop scientists often give rise to several random sources of

variation. Pertinent examples are split-plot designs, series of experiments and repeated

measurements taken on the same field plot. Data arising from such experiments may be

conveniently analysed by mixed models. While the mixed model framework is by now very well

developed theoretically, and good software is readily available, the technology is still

underutilized. The purpose of this talk is to outline basic principles, which help in setting up

mixed models appropriate in a given situation, the main task required from users of mixed model

software. Several examples are considered to demonstrate key issues.

References

Piepho, H.P., Büchse, A., Emrich, K. (2003): A hitchhiker's guide to the mixed model analysis of

randomized experiments. Journal of Agronomy and Crop Science 189, 310-322.

Piepho, H.P., Büchse, A., Richter, C. (2004): A mixed modelling approach to randomized

experiments with repeated measures. Journal of Agronomy and Crop Science 190, 230-247.