Effect of Conservation Agriculture Practices on Physical, Chemical and Biological Attributes of Soil Health Under Soybean–Rapeseed Rotation

Abstract

A four-year field experiment was conducted with soybean–rapeseed rotation on a semiarid subtropical soil to study the influence of conservation agriculture (CA) practices vis-a-vis conventional tillage (CT) on some soil physical, chemical and biological attributes of soil health. Application of fertilizer N, P, farmyard manure (FYM) and crop residues (CR) significantly increased water-stable aggregates and had profound effect in increasing the mean weight diameter as well as the formation of macro-aggregates. After 2 years of soybean–rapeseed rotation under CA practices, the formation of macro-aggregates was the highest in both surface (84 %) and subsurface (80 %) soil layers with application of 20 kg N+60 kg P2O5 + 10 t FYM+4 t rapeseed residue ha−1 applied to soybean and 100 kg N+30 kg P2O5+3 t soybean residue ha−1 applied to rapeseed crop, respectively, and the corresponding values in CT were 83 and 77 %. The same treatment also enhanced total organic C from 4.5 g kg−1 in control to 6.4 g kg−1 in surface layer and from 3.3 to 4.4 g kg−1 in subsurface layer after 4 years in CA practices. Other soil health attributes like labile C and N fractions such as water-soluble C (38.9 mg kg−1), particulate (1483 mg kg−1) and light fraction (209 mg kg−1) organic matter, potentially mineralizable N (23.3 mg kg−1 7d−1) and microbial biomass carbon (283 mg kg−1) were also the highest under this integrated inorganic and organic treatment in conjunction with no tillage (CA practices). These results suggest that CA that integrates application of inorganic fertilizer, organic manure, retention of CR as soil cover, and minimum tillage is tremendously beneficial for soil health due to its positive effects on aggregation processes, augmenting organic matter accumulation and protecting within soil aggregates, and significantly enhancing biological pools in semiarid subtropical soils.