Changes in Organic Carbon, Available Nitrogen and Inorganic N Fractions under Integrated Nitrogen Management of Sorghum in a Mixed Black Soil

A field experiment was conducted to study the effect of inorganic N coupled with composted coirpith and biofertilizers on available N, organic carbon and inorganic N fractions in a mixed black soil (Inceptisol). The intercropping of sorghum + cowpea significantly improved the N status and organic carbon content in the soil and N uptake by sorghum. While sole sorghum accounted for higher grain yield, the intercrop encountered yield reductions to the tune of 6.6 per cent. The N level of 90 kg ha⁻¹ registered higher yield and 120 kg ha⁻¹ recorded higher uptake. Supplementation of organic and bio sources of N enhanced the soil available N, organic carbon, inorganic N fractions and N uptake over fertilizer N alone. The available N and inorganic fractions showed significant positive correlation with N uptake.