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Abstract
Globally, lowland rice contributes more than 70 percent of total rice production, and nitrogen (N) is one of the most yield-limiting nutrients for lowland rice production under all agroecological conditions. A field experiment was conducted for 2 consecutive years to evaluate response of twelve lowland rice genotypes to N fertilization. The N rates used were 0, 50, 100, 150, and 200 kg ha−1. Plant height, grain yield, panicle number, 1000-grain weight, spikelet sterility, grain harvest index (GHI), and nitrogen-use efficiency (NUE; grain yield per unit of N applied) were significantly influenced by N and genotype treatments, except for 1000-grain weight and spikelet sterility, which were not affected by N treatment. Across N rates, genotypes BRS Tropical, BRA 051126, BRA 051130, BRA 05108, and BRA 051134 produced greater grain yields (above average of twelve genotypes) and genotypes BRS Jaçanã, BRA 02654, BRA 051077, BRA 051108, BRA 051129, BRA 051135, and BRA 051250 produced lower grain yield (lower than average yield of twelve genotypes). The GHI and NUE were significantly and positively related with grain yield, while spikelet sterility was negatively related with grain yield. The NUE decreased with increasing N rates and overall 35 kg grain yield was produced with the application of 1 kg N. Genotype BRA 051130 produced maximum NUE (46 kg kg−1) and genotype BRA 051108 produced minimum NUE (24 kg kg−1) among twelve genotypes.