The Influence of Tillage and Crop Residue Management On Soil Quality; A Comparison Between Long-Term Trials in Rainfed and Irrigated Wheat-Maize Systems.

CIMMYT is committed to improving livelihoods in developing countries by increasing the productivity and profitability of farming systems while sustaining natural resources. Conservation agriculture — the use of reduced or zero-tillage, retention of rational amounts of crop residues, and viable crop rotations — can reduce production costs and help meet the need for more economically sound, environmentally friendly, sustainable agricultural production systems for rainfed and irrigated areas. This paper focuses on the influence of tillage and crop residue management on soil quality and includes results from two long-term trials established in the early 1990’s in two contrasting agro-ecological systems in Mexico: (1) a low-input, semi-arid, rainfed system in the central highlands with planting on the flat and (2) a high-input, arid, irrigated system in northwestern Mexico with bed planting. In both systems, zero-tillage with residue retention resulted in higher or comparable yields than the conventional systems and increased soil biological, physical and chemical soil quality. Zero-tillage with residue retention enhanced water availability, soil structure, and nutrient availability more than conventional tillage. Soil microbial diversity increased under zero-tillage with residue retention, facilitating integrated pest management. As well in the rainfed semi-arid zero-tillage system as the irrigated permanent raised bed system, the (partial) retention of the crop residues was necessary to maintain soil quality in zero-tillage systems. The mean weight diameter obtained by dry sieving, aggregate stability, infiltration, irrigation water use efficiency, soil moisture content, soil microbial biomass, micro-flora diversity, micro-flora activity and nutrient status were lower with residue removal than with residue retention. Soil erosion and sodicity increased with residue removal or burning as compared to retaining crop residue at the surface. In light of these results, the underlying principles of conservation agriculture should provide the foundation upon which the development of new agronomic practices is based.