Tillage and residue management effects on soil quality in maize and wheat systems in the highlands of Central Mexico

Intensively cropped highlands areas in the tropics and sub-tropics are susceptible to erosion and declining soil fertility resulting in unsustainable agriculture. Conservation Agriculture has been proposed as an alternative to maize wheat production systems in these agro-ecological zones. A field experiment at CIMMYT's experimental station in Toluca (Mexico) comparing permanent raised beds and conventional tilled beds with different residues management under rain fed conditions was started in 2000. The objective of the research project carried out as part of my internship at CIMMYT was to evaluate the effect of different management practices on chemical and physical soil properties. The challenge was to do this for a trial that was originally designed for technology development and not for scientific research. As a consequence the statistical design was not optimal. ANOVA applied to the whole set of treatments revealed that K concentrations were higher in permanent beds. In addition C was higher in the soils with permanent beds with wheat as crop. Permanent beds showed higher water stable aggregates (wet-sieving) compared to conventionally tilled beds. PCA analysis was performed to assess the underlying structure of the physicochemical variables influenced by tillage, residues and crop. The PC 1 and PC2 of the top-layer (0-5 cm) and sub-layer (5-20 cm) separated conventionally tilled beds from semi- and permanent beds and PC3 separated permanent beds from semipermanent and conventionally tilled beds. These clear separations suggest that tillage and residue management have an effect on soil processes. The research indicates that permanent raised beds increases mainly soil physical soil quality and can be a sustainable production alternative for the (sub )tropic highlands in Mexico when looking at it from a soil quality perspective. Recommendations for future work include recommendations for statistical analyses and comparison of soil quality and yield data to evaluate the feasibility of different management systems in a more unbiased manner.

32 pages