Manure addition influences the effect of tillage on soil aggregation and aggregate associated carbon in a Vertisol of central India

Aim: To study the combined effect of tillage and manure addition on bulk soil and aggregate associated carbon and nitrogen in Vertisol. Methodology: The study was conducted in a long-term tillage experiment having two tillage treatments (reduced tillage and no-tillage) together with100% NPK fertilizer without (T1) and with addition of farm yard manure (T2) @ 2.0 ton C ha-1 to soybean in a soybean-wheat cropping system in a Vertisol of Central India, with three replicates in a split plot design. The parameters studied were aggregate size distribution, mean weight diameter, water stable aggregates, bulk soil and aggregate associated organic carbon, available nitrogen and rate of carbon mineralization. Results: The results indicated significantly higher SOC in reduced tillage (0.87%) than no-tillage (0.71%) under100% NPK fertilization in the bulk soil for 0-15 cm depth. However, 100% NPK + FYM showed a significant increase in the bulk soil organic carbon in the no-tillage treatment only. Available nitrogen content in the bulk soil and aggregate fractions were significantly lower under no-tillage than the corresponding reduced tillage treatments. Manure addition led to significantly higher available N content and proportion of WSA in both the tillage practices. The carbon mineralization was significantly higher by 1.4 to 1.6 times under reduced tillage than no-tillage. Interpretation: Long-term tillage study in Vertisol of Central India indicated reduced tillage to be a better option than no-tillage in maintaining organic carbon and nitrogen availability in soil.