Effect of long term manuring and fertilization on soil aggregation under rice-wheat cropping system in an Inceptisol

Abstract

The long-term effect of manuring and fertilization on aggregate distribution and aggregate associated C was studied under the rice-wheat cropping system in an Inceptisol of the upper Indo-Gangetic plain. Eight treatments from the long term experiment were chosen for this study: control (T1), 100% NPK- fertilizer (T2), 50% NPK- fertilizer + 50 % N-FYM (T3), 75% NPK + 25% N-FYM (T4) and 50% NPK + 50% N-Wheat straw (WS) (T5), 75% NPK + 25% N-WS (T6), 50% NPK + 50% N-Green manure (GM) (T7) and 75% NPK + 25% N-GM (T8). The results revealed that application of balanced chemical fertilizer alone or in conjunction with FYM, WS or GM favoured the soil aggregation and C buildup in the soil. Highest % water stable macro-aggregates (WSMA) (50.49%) and mean weight diameter (MWD) (0.85 mm) were resulted under T3 (50% NPK + 50% N-FYM). Macro-aggregate associated C (MA-C) and micro-aggregate associated C (mA-C) were increased by 48.7 and 126% respectively over control under T6 (75 % NPK + 25 % N- WS). Glomalin content was positively related to the stability of aggregates as indicated by the strong correlation of MWD with glomalin associated with macro-aggregates (GMA) (r=0.74*) and glomalin associated with micro-aggregates (GmA) (r=0.95**).