Conservation Agriculture Training Course, Zimbabwe 2010

C I M M Y TMRInternational Maize and Wheat Improvement Center

The Role and Importance of Residues The Role and Importance of Residues in Conservation Agriculturein Conservation Agriculture

Conservation AgricultureConservation Agriculture Training Course, Zimbabwe 2010 Training Course, Zimbabwe 2010

by Christian Thierfelder


Minimum soil movement Minimum soil movement

Residue retentionResidue retention

Crop rotations and Crop rotations and GMCCsGMCCs

Basic principles of Conservation Basic principles of Conservation AgricultureAgriculture


Residues – what are we talking about?Residues – what are we talking about?

Maize stover Maize stover covering a field covering a field before plantingbefore planting


What are residues? What are residues? continued…. continued….

Maize residues in Maize residues in maize-cotton maize-cotton rotationrotation


Sunnhemp Sunnhemp residues (left)residues (left)

Cotton Cotton residues (right)residues (right)


How to manage residues - rolled maize stalks or How to manage residues - rolled maize stalks or sunnhemp sunnhemp


The challenge – burning of stoverThe challenge – burning of stover

CIMMYT Research StationCIMMYT Research Station


Competing uses for stover residues…!Competing uses for stover residues…!


Water erosionWater erosion

Water infiltrationWater infiltration

Evaporation Evaporation

Soil temperatureSoil temperature

Weed controlWeed control

Soil organic matterSoil organic matter

Soil biological activitySoil biological activity

The Role and Importance of Residues in CAThe Role and Importance of Residues in CA



Impact of raindrop on different soil Impact of raindrop on different soil surfacessurfaces


Crusting and sealing leads to rill erosionCrusting and sealing leads to rill erosion


Amount of soil being eroded after 7 years Amount of soil being eroded after 7 years of bare fallow of bare fallow (plot size 224 m²)(plot size 224 m²)


Treatment Erosion in t ha -1 Runoff l m -2 Conventional ploughing (CP) 11.99 a 545.1 a Direct seeding (DS) 8.01 b 383.9 b Magoye ripper + M. pruriens intercropping (MR) 6.91 b 314.7 b LSD (p ≤ 0.05) 3.50 75.7


About 50% of rainfall is lost on About 50% of rainfall is lost on conventional systemsconventional systems


20 40 60 80

20

40

60

80100

2

4

6

8

Cover %

RelativeErosion %

Residue t/ha

Erenstein, 1997.Erenstein, 1997.Based on data of Shaxon et al., 1989, Based on data of Shaxon et al., 1989, Tripp and Tripp and BBarreto, 1993, and Kok and Thien, 1994.arreto, 1993, and Kok and Thien, 1994.

RelationshipRelationship between residue amount, between residue amount, ground cover and water erosionground cover and water erosion


The soil needs to be permeable (no crusts)The soil needs to be permeable (no crusts)

The soil has to have pores (earthworms)The soil has to have pores (earthworms)

CA plots covered with residues provide for CA plots covered with residues provide for soil micoorganisms, build stable aggregates soil micoorganisms, build stable aggregates (natural swelling and shrinking) and increase (natural swelling and shrinking) and increase the organic matter which all improve the organic matter which all improve infiltrationinfiltration

Why soil erosion? Because water is not Why soil erosion? Because water is not infiltrating!infiltrating!


Pore system has to be unsealed and easy to Pore system has to be unsealed and easy to moisten to enable infiltrationmoisten to enable infiltration


Time to Pond – On-farm ResultsTime to Pond – On-farm Results

Conventional 6.26 b 6.60 bRip-line seed 11.50 a 11.50 aDirect Seed 11.99 a 10.88 aCV% 22.7 23.9SE Diff 1.30 1.24

Shamva Zimuto


Infiltration rate (in l m-2) over time measured by a mini-rainsimulator, Henderson Research Station, Zimbabwe, 2005/2006

Time (min)

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Infil

trat

ion

(in l

m2 )

20

30

40

50

60

70

80

90

100

Conventional Practice (CP)

Direct seeding (DS)Magoye Ripper + Mucuna pruriens (MR)

Cumulative infiltration over time measured by a mini-rainsimulator, Monze, FTC, Zambia, February 2006

Time (min)

0 5 10 15 20 25 30 35 40 45 50 55 60 65In

filtr

atio

n m

m h

-10

20

40

60

80

100

120

Conventional Ploughing (CP)Direct seeding (DS)Basins Planting (BS)

Infiltration is reduced on conventional Infiltration is reduced on conventional systemssystems


Effects of mulch rate on soil water conservation during Effects of mulch rate on soil water conservation during fallow and on subsequent sorghum grain yield, Texasfallow and on subsequent sorghum grain yield, Texas

Source: Unger 1978Source: Unger 1978

Mulch rate, t ha- 1 Precipitation storage , mm Sorghum yield, t ha - 1 0 72 c 1. 8 c 1 99 b 2.4 b 2 100 b 2.6 b 4 116 b 3.0 b 8 139 a 3.7 a

12 147 a 4.0 a


Mulch protects the soil from drying out!Mulch protects the soil from drying out!

Residues reduce radiation energy of the sun - less Residues reduce radiation energy of the sun - less radiation => less evaporationradiation => less evaporation

Drying forces of the wind are lowerDrying forces of the wind are lower

Vapour flux from the soil into the air is reducedVapour flux from the soil into the air is reduced

Capillary uptake in the soil maintains moisture Capillary uptake in the soil maintains moisture transportation from the subsoil to the soil surface transportation from the subsoil to the soil surface


Comparison between capillar uptake in Comparison between capillar uptake in conventional and residue covered soilsconventional and residue covered soils

Conventional:Conventional: Radiation is high at the soil Radiation is high at the soil surface (less cover), surface (less cover),

capillary capillary uptake generally is uptake generally is not not sufficient sufficient from the subsoil. The from the subsoil. The consequence is drying out of the consequence is drying out of the upper layersupper layers

Residue covered:Residue covered: Radiation is lower, capillary Radiation is lower, capillary uptake can be maintained. uptake can be maintained.

Soils supply more Soils supply more moisture for moisture for germination and germination and plant growth.plant growth.


Effect of Crop Residues on Soil Temperature Effect of Crop Residues on Soil Temperature (10 cm Depth)(10 cm Depth)

Bare soil

Days in August 1973

Tem

pera

ture

(°C

)

Source : Lal, 1978


Effects of different residues on weed soil cover (in %) and Effects of different residues on weed soil cover (in %) and weed population (plants/mweed population (plants/m22) 7 and 58 day after roling) 7 and 58 day after roling

Source: Almeida and Rodríguez, 1985Source: Almeida and Rodríguez, 1985

2219

9

0 0

7

27

56

0

10

20

30

40

50

60

70

Mulch material

Wee

d co

ver (

%)

7 Days

139

5 26

31

83

6

0

10

20

30

40

50

60

70

80

90

100

Mulch materialW

eed

popu

latio

n (p

lant

s/m

2 )

58 days


Residues build up the humus in the Residues build up the humus in the soilsoil

„„TheThe organic organic matter in matter in tropical soils is, tropical soils is, besides besides moisture, more moisture, more important than important than any other soil any other soil characteristic“ characteristic“ Young, 1976Young, 1976


Residues increase organic carbon content over timeResidues increase organic carbon content over time

Plant available phosphorus, potassium, calcium and Plant available phosphorus, potassium, calcium and magnesium increases have been reportedmagnesium increases have been reported

Residues may lead to nitrogen lock-up initially Residues may lead to nitrogen lock-up initially especially when soils are very limited in nitrogen especially when soils are very limited in nitrogen (microbes use the nitrogen for their biomass)(microbes use the nitrogen for their biomass)

After some years the system is in equilibrium, N After some years the system is in equilibrium, N immobilization will no longer negatively effect nutrient immobilization will no longer negatively effect nutrient availabilityavailability

Effects of residues on nutrient availabilityEffects of residues on nutrient availability


Decomposition in tropical climateDecomposition in tropical climate

Surface effects (protection, temperature, moisture Surface effects (protection, temperature, moisture retention, fodder for soil fauna and flora)retention, fodder for soil fauna and flora)

Slow nutrient release Slow nutrient release

Build-up of organic matter poolBuild-up of organic matter pool

Why is surface residue retention important? Why is surface residue retention important?


40%

32%Microbial

DecompositionAsh

CO2

CO2

Soil OM 8%

Crop Residue

CO2 92%60%

Burn

Soil OM

Crop Residue

Microbial Decomposition

CO2 80%

20%

No Burn

Source: Albrecht et al., 1994 USDA-ARS Pendleton, OR


Residues encourage earthworm Residues encourage earthworm activityactivity



Effective destruction by ants and termites, fungi Effective destruction by ants and termites, fungi and bacteriaand bacteria


Lignin contentLignin content C:N ratioC:N ratio Microbial preferences (maize/sunflower)Microbial preferences (maize/sunflower) Microbial variability (clay soils)Microbial variability (clay soils) Soil moisture contentSoil moisture content TemperatureTemperature pH pH

Factors influencing decompositionFactors influencing decomposition


Effect of residue addition on biological activity (% increase in biological activity over control)

Day Wheat straw burned stubbles 1 80 29

4 61 9

7 47 0

10 28 0

Source: Albrecht et al., 1994 USDA-ARS Pendleton, OR


Problems and challenges with residues Problems and challenges with residues (pests and diseases carry over)(pests and diseases carry over)

Perithecia of Perithecia of Pyrenophora Pyrenophora trichostoma trichostoma ((Helminthosporium tritici-Helminthosporium tritici-repentisrepentis) on wheat straw) on wheat straw


Residues increase micro-, meso,- and macro-fauna Residues increase micro-, meso,- and macro-fauna thus facilitating a biological equilibriumthus facilitating a biological equilibrium

If a system is in If a system is in equilibrium, insects equilibrium, insects and pests are and pests are controlled by their controlled by their predatorspredators


Some people just prefer „clean“ fieldsSome people just prefer „clean“ fields

The mindset is very The mindset is very importantimportant



Thank you very much!Thank you very much!

Documents

Conservation Agriculture Training Course, Zimbabwe 2010