Continuous Rice Cropping System with Integrated Use of Inorganic and Organic Sources of Nutrients for Soil Quality Improvement

Maintenance of soil quality is considered to be the key to attain sustainability in agricultural production and thus to achieve food security. In this study we tried to answer a research question as to whether integrated application of inorganic and organic sources of nutrients can maintain productivity and soil quality in rice-rice cropping system. To address this, total 27 physical, chemical (including organic C and soil fertility parameters) and biological (including enzyme activities) properties of an acidic sandy loam soil, which were subjected to different nutrient management (NM) practices for nine years of rice-rice cropping under submergence in subtropical India were critically assessed. Seven NM practices comprised of organic [farmyard manure (FYM)], inorganic fertilizers (sources of N, P, K, S, Zn, and B) and some of their combinations were tested using randomized complete block design with four replications. Integrated use of inorganic fertilizers (NPK) and organic manure (FYM) sustained productivity of rice-rice cropping system and aggraded soil quality as compared to only inorganic fertilizers even with inclusion of S, Zn and B. The NPK+FYM was superior among the NM practices to improve physical, chemical and biological properties of soil. Cation exchange capacity, non-exchangeable K and microbial biomass C were screened as the most sensitive attributes for assessing soil quality. Although the present study demonstrated the positive influence of integrated NM, application of even 80-17.5-50 kg N-P-K along with 5 Mg FYM ha-1 in each rice season failed to maintain total K content in soil. This suggested for readjustment of dose of inorganic fertilizers and organic manure and their application schedule for adequate replenishment of K in acidic sandy loam soil under rice-rice cropping in subtropical climate.