Long-term effects of organics, fertilizers and cropping systems on soil physical productivity evaluated using a single value index (NLWR)

Effect of different cropping systems, viz. maize–wheat (M–W), rice–wheat (R–W), soybean–wheat (S–W), and perennial grasses (guinea grass and setaria grass), in vogue since 6–32 years, and long-term use of chemical fertilizers (N, NP, NPK and NPK + lime) and organic materials (FYM, wheat straw, lantana biomass) on physical productivity of medium-textured (silt loam and silty clay loams) soils was investigated using non-limiting water range (NLWR) as the soil physical index. Higher the NLWR better is the soil physical condition for crop growth. The sources of N, P and K were urea, single superphosphate and muriate of potash, respectively. The NLWR was highest in S–W (16.8%), followed by grasses (14.4–15.6%) and M–W (13.1–15.4%), and lowest in R–W (7.5–11.0%). Under M–W system (32 years), NLWR was highest in NPK (13.1%), followed by NP (12.2%), NPK + lime (9.4%) and control (9.0%), and lowest in N (7.7%). Application of organics increased the NLWR in both M–W and R–W (6–18 years) systems; the NLWR values with and without organics were 18.0 and 17.1% in M–W, and 14.1–15.9 and 15.7–17.2% in R–W system. The NLWR was linearly, significantly and positively correlated with wheat grain yield (r = 0.646**, −0.706**). The NLWR:PAWC (plant available water capacity) ratio (higher the ratio, better is the soil physical condition), which was 0.58 in control, decreased with N (0.49) but increased with NP (0.72) and NPK application (0.77); use of organics further improved the ratio. The NLWR:PAWC ratio was highest in S–W (0.97), followed by grasses (0.88–0.91), M–W (0.77–0.86) and R–W (0.54–0.68) system. Thus, long-term use of urea alone deteriorated, while NPK at recommended rates improved soil physical productivity over the control of no fertilizer application; the effect further improved when NPK were combined with organic sources. Among different cropping systems, the soil physical productivity followed the order: S–W > grasses > M–W > R–W system.