Combining Vermicompost with Inorganic Fertilizers Improved Rice Yield and Affected Potassium Pools under Rice-Based Cropping Systems in Inceptisols

Integrated use of inorganic fertilizer and organic manure restores soil quality and increases crop productivity. Potassium (K) pools are also affected in soil due to the rate and sources of nutrients applied. However, the integration of vermicompost and mineral fertilizers effects strongly depends on soil type, and still, no precise information is available for Inceptisols in Eastern India. Keeping this fact in view, a field experiment was conducted at the research farm of Bihar Agriculture University, Sabour, Bihar to understand the effect of soil test crop response (STCR) based balanced fertilization with or without organic manure on soil K pools and rice performance under rice-wheat and rice-maize cropping systems. This experiment included nine treatments viz., general fertilizer recommendation, farmers’ fertilizer practice, STCR with and without Integrated Plant Nutrient System (IPNS)/vermicompost for low (3 t ha−1), medium (4 t ha−1), and high target yield (5 t ha−1) and absolute control (without fertilizer application) which were replicated thrice in a randomized block design (RBD). The highest rice yield was obtained under STCR with IPNS for high target yield (2% more) than the corresponding treatment without IPNS followed by STCR with IPNS for medium target yield however treatments were statistically at par with one another. Benefit cost ratio was significantly highest under STCR with IPNS for medium target yield overall the treatments for both cropping systems. Different forms of K (water-soluble K, exchangeable K, non-exchangeable K, and mineral K) declined under farmers’ practice and absolute control whereas these forms were greater under STCR with IPNS-based treatments than the STCR without IPNS-based treatments in the corresponding target yields. The correlation study suggested that exchangeable K was the most important form, positively and highly significantly related to soil available K (R2 = 98). Overall, this study recommended that the integrated use of vermicompost and mineral fertilizers (STCR with IPNS) for medium target yield (4 t ha−1) was more responsive toward rice yield as well as K availability for soil sustainability from Inceptisols in eastern India.