Influence of cropping systems on soil biochemical properties in an arid rain-fed environment

The effect of eight crop rotations was studied for 3 years (1990–92) on enzyme activities, nitrifying bacteria, VAM spores, organic matter, NO3-N and available-P. Inclusion of the legume crops, clusterbean or mungbean in the rotation had a beneficial effect on these parameters over fallow-pearl millet resulting in a significant increase in pearl millet production. Continuous clusterbean for 3 years in rotation gave the maximum increase in soil organic matter, NO3-N, available P and enzyme activities (dehydrogenase, acid and alkaline phosphatases, nitrogenase) over continuous pearl millet while the trend was reversed for nitrifying bacteria and VAM spores population. In general, the effect on soil biochemical properties was greater in surface soil (0–15 cm) than subsoil. However, the build up of VAM spores was greater in subsoil. The results demonstrate that in arid sandy soils, in order to improve soil quality, legumes, particularly clusterbean, should appear for more than 1 year successively in legume–cereal rotations.