Soil physical fertility and crop performance as affected by long term application of FYM and inorganic fertilizers in rice–wheat system

Soil fertility, one of the important determinants of agricultural productivity, is generally thought to be supplemented through the application of nutrients mainly through inorganic fertilizers. The physical fertility of the soil, which creates suitable environment for the availability and uptake of these nutrients, is generally ignored. The present study aims to characterize the soil physical environment in relation to the long term application of farm yard manure (FYM) and inorganic fertilizers in rice–wheat. The treatments during both rice and wheat crops were (i) farm yard manure @ 20 t ha−1 (FYM); (ii) nitrogen @ 120 kg ha−1 (N120); (iii) nitrogen and phosphorus @ 120 and 30 kg ha−1 (N120P30) and (iv) nitrogen, phosphorus and potassium @ 120, 30 and 30 kg ha−1 (N120P30K30) in addition to (iv) control treatment, i.e. without any fertilizer and/or FYM addition. The treatments were replicated four times in randomized block design in a sandy loam (typic Ustipsament, non-saline, slightly alkaline). Bulk density, structural stability of soil aggregates and water holding capacity of 0–60 cm soil layer were measured.The average mean weight diameter (MWD) was highest in FYM-plots both in rice (0.237 mm) and wheat (0.249 mm) closely followed by that in N120P30K30 plots. The effect of FYM in increasing the MWD decreased with soil depth. The addition of both FYM and N120P30K30 increased the organic carbon by 44 and 37%, respectively in rice. The total porosity of soil increased with the application of both FYM and N120P30K30 from that in control plots. In 0–15 cm soil layer, the total porosity increased by 25% with FYM from that in control plots. This difference decreased to 13% in 15–30 cm soil layer. The average water holding capacity (WHC) was 16 and 11% higher with FYM and N120P30K30 application from that in control plots. The MWD, total porosity and WHC improved with the application of balanced application of fertilizers. The grain yield and uptake of N, P and K by both rice and wheat were higher with the application of FYM and inorganic fertilizers than in control plots. The carbon sequestration rate after 32 years was maximum (0.31 t ha−1 year−1) in FYM-plots, followed by 0.26 t ha−1 year−1 in N120P30K30-plots, 0.19 t ha−1 year−1 in N120P30 and minimum (0.13 t ha−1 year−1) in N120-plots.