High weed infestation and low nitrogen (N) recovery are among the major causes of lower yield in dry-seeded rice (DSR) compared with transplanted rice. The effects of N rate and planting density dynamics on rice productivity and N-use efficiency (NUE) have been extensively studied in transplanted rice. However, information on the combined impact of N rates, weed regimes, and crop plant densities on rice productivity and NUE is very limited in DSR systems. Attaining synchrony between crop demand and N supply is a key in optimizing the tradeoffs amongst environmental pollution, kernel yield, and profit. Experiments were conducted in 2012 and 2013 to assess the impact of weed regimes (partial weedy and weed-free), N rates (0, 100, 150, and 200 kg ha−1), and rice seeding rates (50 and 100 kg ha−1) on crop productivity, N efficiency indices, and synchronization between crop demand and N supply. The seeding rate of 50 kg ha−1 was better when the sunlight was not a limiting factor. The application of 150 kg N ha−1 produced higher yield-contributing attributes and grain yield (5.2–6.6 t ha−1) of rice than 100 (4.7–5.6 t ha−1) and 200 kg N ha−1 (4.9–6.5 t ha−1). The highest physiological efficiency (40–53 kg grain kg−1 N uptake by plants) was achieved at 150 kg N ha−1. Partial factor productivity was higher in the plots applied with 150 kg N ha−1 than with 200 kg N ha−1. The best degree of synchrony between crop N demand and supply was achieved at 150 kg N ha−1. The results of this study suggest that for harvesting better grain yield, DSR crop should be planted using a seed rate of 50 kg ha−1 in combination with 150 kg N ha−1.
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