Soil Aggregation Controls Biological Activities on Long-Term Integration of Organic Amendments and Inorganic Fertilizers in Rice-Wheat Cropping System

Integrated nutrient management (INM) practice with farmyard manure (FYM), wheat straw (WS) and green leaf manuring (GLM) augments aggregate formation in soils. However, soil aggregation regulating several soils biological activities has been proven to be intricate with both positive and negative interactions across studies. We studied the distribution of soil organic carbon (SOC), microbial biomass carbon (MBC) and soil enzymes across three aggregate classes (>2000 mu m, 2000-250 mu m and <250 mu m) from a long-term rice-wheat cropping system. Integrated nutrient management practices significantly influence the fraction of soil macro-aggregates; whereas suboptimal level of fertilization was dominated by micro-aggregates. Application of inorganic fertilizer with FYM over long-term improves SOC to the tune of 12.78% when compared with 100% recommended dose of fertilizers (RDF); whereas WS as an amendment improves MBC to the tune of 51.80% over RDF. Activities of the studied soil enzymes (Acid phosphatase, Alkaline phosphatase, Dehydrogenase, Fluorescein Diacetate Hydrolysing Capacity and Urease) were found to be higher when associated with large macro-aggregates fraction of size >2000 mu m as compared to micro-aggregates. In conclusion, large macro-aggregates improve and regulate all the soil biological indicators after a long-term integration of organic amendments with inorganic fertilizers.