Risk of soil compaction in energy crop rotations with and without sugar beet Philipp Götze1*, Jan Rücknagel1, Anna Jacobs2, Olaf Christen1

1Institute of Agricultural and Nutritional Sciences, Department Agronomy and Organic Farming, Martin Luther University Halle-

Wittenberg, Betty-Heimann-Str.5, 06120 Halle; 2Institute of Sugar Beet Research, Holtenser Landstrasse 77, DE - 37079

Goettingen; *contact via philipp.goetze@landw.uni-halle.de

When producing biogas it is beneficial to cultivate crops that achieve the highest methane yields – and thus the highest dry matter yields – across a given area. With this in mind,

given the conditions in Central Europe sugar beets represent an alternative to silage maize. However, cultivating these crops to produce biogas must fulfil the criteria of

sustainable agricultural production. This article deals with evaluating the risks of soil compaction damage associated with entire crop rotations with and without sugar beet. This is

based on a model farm which is assumed to use modern, standard equipment as well as based on the operations and the respective dates performed during a field trial.

Crop

Rotation

2004

2007

2010

2005

2008

2011

2006

2009

2012

1 1 SM SM SM

2 1 Mu_SB WW WW

2 WW WW Mu_SB

3 WW Mu_SB WW

3 1 Mu_SM WW WW

2 WW WW Mu_SM

3 WW Mu_SM WW

4

1 SB WW Mu_SM

2 WW Mu_SM SB

3 Mu_SM SB WW

Tab. 1: Crop rotations on field site

Aiterhofen.

(SB – Sugar Beet, SM – Silage Maize, WW –

Winter Wheat, Mu - Mustard catchcrop).

Operation WoWi (m) Axle

Load (kg) Tyre Size TIP (bar)

Primary tillage 3 5506 650/65 R 42 0.8 … … … … …

Seed Sugar Beet 6 3480 420/85 R 34 0.8 … … … … …

Plant protection | Tractor 21 3316 420/85 R 34 0.8

Plant protection | Trailer 21 3812 420/85 R 38 0.8 … … … … …

Harvest Sugar Beet 100% hopper load 3 26180 1050/50 R 32 2.7

Harvest Sugar Beet 50 % hopper load 3 20790 1050/50 R 32 2.0

Fig. 1: Seasonal course and annual variation in soil

water content for sugar beet, modelled for the 0-60 cm

soil layer (period 2004-2012).

Tab. 2: Sample of machine data used for modelling.

(WoWi – working width, TIP- tyre inflation pressure).

Rücknagel, J., Hofmann, B., Deumelandt, P., Reinicke, F., Bauhardt, J., Hülsbergen, K.-J., Christen, O. (2015):

Indicator based assessment of the soil compaction risk at arable sites using the model REPRO. Eclog. Ind. 52,

341-352.

Hülsbergen K.-J. (2003): Entwicklung und Anwendung eines Bilanzierungsmodells zur Bewertung der

Nachhaltigkeit landwiitschaftlicher Systeme. Shaker Verlag, Aachen. ISBN: 3-822-1464-X

Fig. 3: Soil Compaction Index and respective soil

compaction risk at 20 cm soil depth. Fig. 4: Soil Compaction Index and respective soil

compaction risk at 35 cm soil depth.

• At both soil depths, the modelled

soil compaction risks are higher

for the crop rotations with SB

than those without SB.

• The increased soil compaction

risk is largely influenced by the

SB harvest in years where soil

water content is high.

• Halving the hopper load and

adjusting tyre inflation pressure

reduces the soil compaction risk

for the crop rotations as a whole.

Under these conditions, there are

only minor soil compaction risks

for all variants in the subsoil (35

cm).

A crop rotation field trial in Aiterhofen (Germany, Lover Bavaria) forms

the basis of these investigations. The cultivation dates from the field trial

are used to model the soil compaction risk for each crop rotation field in

each year.

Based on assumptions of the equipment currently used in

practice by a 75 ha model farm, two scenarios are modelled

(100 % and 50 % hopper load for SB and WW harvest).

Soil compaction risk is modelled based on the method by

Rücknagel et al. (2015) using the software REPRO (Hüls-

bergen 2003). In this model, the soil strenght (precompres-

sion stress σp) is contrasted with the vertical soil stress

(major principle stress σz) at he respective soil depth (20

and 35 cm).

Soil water content (% field capacitiy, FC)

is modelled on a daily basis by the

German Meterological Service (Fig. 1,

Straubing Station, texture silt loam, 38

Vol.% FC) and for the crops sugar beet,

silage maize and winter wheat.

Soil samples were taken in 2013 to

determine the mechanical precompression

stress. This is log 1.91 (= 81.3 kPa) for the

topsoil (20 cm) and log 1.86 (= 72.4 kPa)

for the subsoil (35 cm).

Acknowledgements

The project was founded by the Fedral Ministry of Food and Agriculture by

a decision of the German Bundestag and via the Fachagentur Nachwachs-

ende Rohstoffe e.V. within the joint project “The sugar beet as an energy

crop in crop rotations on highly productives sites – an agronomic / eco-

nomic system analysis“. Refe

rences

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MARTIN LUTHER UNIVERSITY

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Tab. 3: Classification of the soil com-

paction risk depending of the calculated

Soil Compaction Index.

Soil Compaction Index (SCI)

Soil compaction risk

≤0.1 low

0.11 – 0.2 middle

0.21 – 0.3 high

0.31 – 0.4 very high

> 0.4 extremely high