Medium-term impact of tillage and residue management on soil aggregate stability, soil carbon and crop productivity.

Paul BK, Vanlauwe B, Ayuke F, Gassnerc A, Hoogmoed M, Hurissoa TT, Koala S, Lelei D, Ndabamenyea T, Six J. "Medium-term impact of tillage and residue management on soil aggregate stability, soil carbon and crop productivity." Agriculture, Ecosystems and Environment. 2013;164:14-22.


Conservation agriculture is widely promoted for soil conservation and crop productivity increase,
although rigorous empirical evidence from sub-Saharan Africa is still limited. This study aimed to quantify
the medium-term impact of tillage (conventional and reduced) and crop residue management (retention
and removal) on soil and crop performance in a maize–soybean rotation. A replicated field trial
was started in sub-humid Western Kenya in 2003, and measurements were taken from 2005 to 2008.
Conventional tillage negatively affected soil aggregate stability when compared to reduced tillage, as
indicated by lower mean weight diameter values upon wet sieving at 0–15 cm (PT < 0.001). This suggests
increased susceptibility to slaking and soil erosion. Tillage and residue management alone did not affect
soil C contents after 11 cropping seasons, but when residue was incorporated by tillage, soil C was higher
at 15–30 cm (PT*R = 0.037). Lack of treatment effects on the C content of different aggregate fractions
indicated that reduced tillage and/or residue retention did not increase physical C protection. The weak
residue effect on aggregate stability and soil C may be attributed to insufficient residue retention. Soybean
grain yields tended to be suppressed under reduced tillage without residue retention, especially
in wet seasons (PT*R = 0.070). Consequently, future research should establish, for different climatic zones
and soil types, the critical minimum residue retention levels for soil conservation and crop productivity.
Keywords: Reduced tillage, Crop residue management, Soil aggregate stability, Crop yields, Soil organic, carbon, Sub-Saharan Africa

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