Yield and Soil Organic Matter Dynamics as Affected by the Long-Term Use of Organic and Inorganic Fertilizers Under Rice–Wheat Cropping System in Subtropical Mollisols

Abstract

Effect of long-term application of fertilizer NPK alone or in combination with farmyard manure (FYM) to an annual rice–wheat cropping system (initiated in 1971) on a typic Hapludoll soil was studied on the physical and chemical properties as well as soil organic carbon fractions. Results revealed that continuous cropping of rice–wheat over the period of 42 cycles without NPK fertilizers reduced grain yields of rice and wheat by 80.0 and 45.4% over its initial level of 6.3 and 2.2 t ha−1, respectively. Application of 100% NPK (120 kg N + 60 kg P2O5 and 40 kg K2O) + FYM @ 10 t ha−1 produced the highest grain yield of rice of 5.2 t ha−1 and wheat of 4.7 t ha−1. Conjoint use of 100% NPK and FYM increased the organic carbon content by 7.4 and 10.1% in soil after rice and wheat harvest, respectively, over initial level of 1.48%, and it decreased by 39.2–44.6% and 36.8–49.1% in other NPK fertilizers treatments. In the control treatment, organic C was reduced it to about one-third of the value recorded at initiation of the experiment. In the absence of P, K, S, and Zn addition, continuous cropping drastically reduced their availability in soil over the years. However, no perceptible change in pH was observed. Physical properties were improved with integrated use of fertilizers and manure. Total organic carbon and its different active and passive pools C fractions in soil were influenced significantly with fertilizer management practices and were positively correlated with yields and most of the soil properties. Among soil properties, available K and hydraulic conductivity were found to be more closely correlated with soil C fractions.