A long-term experiment initiated in 1983 was selected during 1997–99 to study cumulative impact of organic sources (FYM, rice straw and green karanj leaves) substituting inorganic fertilizers in recommended fertilizer dose (RFD) once each by 25% and 50% during rainy season (kharif, in maize (Zea mays L.)–wheat (Triticum aestivum L. emend. Fiori & Paol.) cropping system. All the organic sources were instrumental in improving pH and aggregation of soils. Only rice straw in its higher substitution (50%) could induce significant improvement in bulk density and water-holding capacity of soils but a constant trend of improvement was there under application of all the sources. All the 3 sources both in their higher and lower substitutions enriched the soils in organic carbon contents. Farmyard manure (FYM) and green karanj leaves in their higher substitution improved NPK levels of soils. Rice straw at this level (50% substitution) could bring about significant improvement only in available K content of soils. At lower level of substitution (25%) green manuring with karanj leaves induced higher available P and K in soils, but FYM at the level could bring about significant improvement only in available P level. Application of rice straw at this level of substitution (25%) could not alter status of any of the NPK significantly. Substitution of inorganic fertilizers by FYM either at higher (50%) or lower (25%) level was helpful in increasing grain yield and uptake of NPK.
Integrated nutrient management, Maize–wheat system, Nutrient uptake, Soil fertilizer.
