Nutrient Uptake and Apparent Balances for Rice-Wheat Sequences. I. Nitrogen

ABSTRACT Nitrogen (N) nutrition of the rice-wheat (RW) systems of the Indo-Gangetic Plain is important for sustaining the region's productivity and food needs. Soil N plays an important role in regulating the supply of N to plants. Monitoring plant concentrations, uptake, and balance of N assist in our understanding of plant and soil N status and in devising N-fertilizer strategies for both individual crops and a cropping system. Field experiments with rice-wheat-mungbean and rice-wheat-maize annual cropping sequences were conducted at Joydebpur, Nashipur, and Ishwordi in Bangladesh, which differ in their soils and climates. The experiments compared three pre-rice treatments (mungbean residues retained, mungbean residues removed, and maize residues removed), supplying each with two fertilizer levels (soil-test based, or STB, and farmers' practice, or FP). Zero N (control) treatments were included, with all other nutrients applied as STB or FP. The objectives were to detect N deficiency, if any, in the com...