Optimization of organic and inorganic nitrogen for rainfed maize (Zea mays) in dry sub-humid Inceptisols

Abstract

A field experiment on maize (Zea mays L.) was conducted in rainy season (kharif) during 1998 to 2005 with a set of nine fertilizer treatments in separate blocks of maize, blackgram and maize + blackgram under dry sub-hu- mid inceptisols of Jammu. An attempt was made to select an efficient treatment that has maximum sustainability over years, apart from optimizing organic and inorganic fertilizer N for different crop-seasonal rainfall situations to attain maximum maize yield. The analysis of variance indicated that treatments differed significantly from each other every year and also pooled over years. Treatment-wise regression models of yield were calibrated as a func- tion of crop-seasonal rainfall and crop-growing period to assess the sustainability of treatments. Application of N @ 60 kglha proved superior in maize and maize + blackgram blocks, whereas 15 kg N (Leucaena) + 20 kg N (urea) was superior in blackgram block. A pooled regression model of yield as a function of rainfall, crop-growing period and fertilizer N was used to derive optimum fertilizer N at different rainfall situations. The inorganic and or- ganic N ranged from 44 to 57 kglha and 23 to 27 kglha respectively at 700 mm rainfall, and from 56 to 73 kglha and 27 to 31 kglha respectively at 1,100 mm rainfall for attaining maximum maize yield in different blocks. The cor- responding doses of inorganic and organic N ranged from 39 to 49 kglha and 18 to 22 kglha at 700 mm compared with 51 to 65 kglha and 22 to 26 kglha at 1,100 mm for attaining economic yield of maize.