Conjoint Application of Organic and Inorganic Sources of Nutrients on Yield, Nutrient Uptake and Soil Fertility under Rice (Oryza sativa)–Wheat (Triticum aestivum) System

Abstract

A field experiment was conducted for three years on a sandy loam soil at Varanasi, Uttar Pradesh to study the direct effect of three sources of organic manures i.e., sewage sludge (SS), vermicompost (VC) and Sesbania green manure (GM) in combination with 75% of recommended fertilizers (RDF). Other treatments were: absolute control, 100% RDF + SZnB and customized fertilizer (CF) under rice-wheat system. Grain yield of rice in RDF + SZnB and CF was statistically at par with RDF (4.47 t ha-1). Supplementing 25% N through SS resulted in a significant decrease in grain yield of rice over RDF. However, grain yield of rice was at par with RDF when 25% N was supplemented through VC or GM. In following wheat, grain yield was similar under all the treatments except for absolute control (without fertilizers), which produced significantly lower yields. Application of VC or GM at 25% of recommended N could sustain the yield of rice-wheat system along with 75% RDF. Total removal of N, P, K, S, Zn and B was higher by rice than wheat, indicating its nutrients exhaustive nature. Soil pH and EC did not change significantly with the application of organic and inorganic sources of nutrients. Organic carbon content in soil increased significantly by supplementing fertilizers with organic sources. Differential pattern of nutrient build-up was recorded in the post-harvest soil samples. In post-rice soil, N, K and S did not show significant build-up while P and Zn contents increased significantly. Application of S, Zn and B significantly increased their contents in soil over RDF. In post wheat harvest soil, application of CF showed a significant increase in P content. Application of organics over three years resulted in a significant increase of Zn over 100% RDF.