Assessment of GMean biological soil quality indices under conservation agriculture practices in rainfed Alfisol soils.

The present study was conducted in 2009-10 with the objective to monitor the effect of restorative soil management practices on biological soil quality. The experiment was initiated in 1995 in a strip-split-split plot design with three replications. Sorghum and castor were grown in two-year rotations. The procedure comprised of two tillage treatments: conventional tillage (CT) and minimum tillage (MT; main plots), three residues treatments: sorghum stover (SS), Gliricidia loppings (GL), no residue (NR; sub-plots), and two nitrogen levels 0 (N0) and 90 kg ha-1 (N90) (sub-subplots). After 15th year of the experiment, activities of the soil enzymes, microbial biomass carbon (MBC), labile carbon (LC) and organic carbon (OC) were studied. Soil management treatments significantly influenced the soil enzyme activities. Enzyme activity was significantly correlated with MBC, LC and OC. The biological soil quality has been assessed in terms of GMeanBSQI (geometric mean of biological soil quality index). From the viewpoint of GMeanBSQI, the order of superiority of soil management treatments was: MT (0.82) > CT (0.69). The performance of the residues was in the order GL (0.87) > SS (0.75) > NR (0.65). Nitrogen @ 90 kg ha-1 (0.81) proved superior to no nitrogen (N0 - 0.70). Among all the treatment combinations, MTGLN90 was found to be the most superior management option for ensuring higher GMean in rainfed Alfisol soils. The present study indicates that crop residue management under minimum tillage is of great significance in improving the biological soil quality indicators and indices. The results obtained are significant in improving biological soil quality index and crop productivity through appropriate soil management. [ABSTRACT FROM AUTHOR]