CIMMYT is committed to improving livelihoods in developing countries by improving the productivity and profitability of farming systems while sustaining natural resources. This paper focuses on the influence of crop residue management on soil quality in zero till systems and includes results from two long-term trials established in the early 1990?s in different agro-ecological systems in Mexico: (1) a low-input, semi-arid, rainfed system in the rainfed central highlands (2240 masl) with zero tillage on the flat and (2) a high-input, arid, irrigated system in the northwestern part of the country with zero tilled permanent raised beds. In both zero till systems, the (partial) retention of the crop residues was necessary to maintain soil quality. In the rainfed semi-arid zero tillage system, mean weight diameter obtained by dry sieving, aggregate stability, infiltration, soil moisture content, soil microbial biomass and nutrient status were lower with residue removal than with residue retention. In the irrigated permanent raised bed system, burning of all crop residues resulted in a degradation of soil structure, lower direct infiltration, irrigation efficiency, soil moisture content, soil microbial biomass, lower total N and greater soil sodicity as compared to retaining crop residue at the surface. Practices with partial retention of crop residue showed soil quality similar to practices with retention of all residues. The retention of at least part of the crop residue is essential for the sustainability of zero till systems, although it may be possible to remove part of the residue for other uses, especially in irrigated conditions where biomass production is high.

Conservation Agriculture Program

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INT2813|INT3307|CSAY01