Productivity and nutrient-use efficiency of soybean (Glycine max) and sorghum (Sorghum bicolor) intercropping at different levels of nitrogen in rainfed deep vertisols

A field experiment was conducted during the rainy season of 2000 and 2001 on deep Vertisols of Bhopal, to study the effect of soybean [Glycine max (L) Merr.] and sorghum [Sorghum bicolor (L.) Moench] intercropping (2:1 row ratio) in comparison to their sole crops at 3 levels of nitrogen (0, 75 and 100% recommended dose). Sole sorghum recorded higher seed, straw and soybean-equivalent yield (SEY) compared to either sole soybean or soybean + sorghum intercropping. However at N₀, soybean + sorghum intercropping resulted in higher SEY and at higher N status (75 or 100%), sole sorghum resulted in higher SEY. Nitrogen-uptake was higher in sole soybean, whereas P and K uptake were higher in sole sorghum. Sole sorghum recorded higher nutrient-use efficiency (NUE), whereas sole soybean resulted in iower NUE. However, nutrient harvest index of NPK were higher in sole soybean and lowest in sole sorghum. Increased N levels significantly improved the SEY, nutrient uptake and agronomic and recovery efficiency of NPK. However, physiological efficiency and nutrient harvest index of NPK were not affected due to increased N levels.