Effects of Long Term Application of Inorganic and Organic Fertilizers on Soil Organic Carbon and Physical Properties in Maize–Wheat Rotation

Balanced and integrated use of organic and inorganic fertilizers may enhance the accumulation of soil organic matter and improves soil physical properties. A field experiment having randomized complete block design with four replications was conducted for 36 years at Punjab Agricultural University (PAU), Ludhiana, India to assess the effects of inorganic fertilizers and farmyard manure (FYM) on soil organic carbon (SOC), soil physical properties and crop yields in a maize (Zea mays)–wheat (Triticum aestivum) rotation. Soil fertility management treatments included were non-treated control, 100% N, 50% NPK, 100% NP, 100% NPK, 150% NPK, 100% NPK + Zn, 100% NPK + W, 100% NPK (-S) and 100% NPK + FYM. Soil pH, bulk density (BD), electrical conductivity (EC), cation exchange capacity, aggregate mean weight diameter (MWD) and infiltration were measured 36 years after the initiation of experiment. Cumulative infiltration, infiltration rate and aggregate MWD were greater with integrated use of FYM along with 100% NPK compared to non-treated control. No significant differences were obtained among fertilizer treatments for BD and EC. The SOC pool was the lowest in control at 7.3 Mg ha⁻¹ and increased to 11.6 Mg ha⁻¹ with 100%NPK+FYM. Improved soil physical conditions and increase in SOC resulted in higher maize and wheat yields. Infiltration rate, aggregate MWD and crop yields were positively correlated with SOC. Continuous cropping and integrated use of organic and inorganic fertilizers increased soil C sequestration and crop yields. Balanced application of NPK fertilizers with FYM was best option for higher crop yields in maize–wheat rotation.