Effects of time of first harvest, total amount of nitrogen, and nitrogen application method on total dry matter yield in twice harvesting of rice

Abstract

We examined the effects of time of first harvest, total amount of nitrogen, and nitrogen application method on the total dry matter yield of a twice-harvested rice ( Oryza sativa L.) cultivar Taporuri grown in southwestern Japan. The highest total dry matter yield was 27.1 t ha −1. We examined the effects of two times of first harvest (booting stage versus full heading stage). Plants harvested at the full heading stage produced 50% higher dry matter yield of first crop than those harvested at the booting stage, because the plants had greater weights per tiller than those harvested at the booting stage. Plants harvested at the booting stage produced 37% higher dry matter yield of second crop than those harvested at the full heading stage, because the plants had greater dry weights per tiller than those harvested at the full heading stage. Overall, plants harvested at the full heading stage produced 8% higher total dry matter yield than those harvested at the booting stage. We also examined the effects of two total amounts of nitrogen (300 kg N ha −1 versus 150 kg N ha −1) and three nitrogen application methods (method 1: 33.3% applied at transplanting, 66.7% at the maximum tiller number stage, 0.0% at 7 days after the first harvest, and 0.0% at 21 days after the first harvest; method 2: 33.3, 33.3, 16.7, and 16.7%, respectively; method 3: 33.3, 0.0, 33.3%, and 33.3%, respectively). For the first crop, plants that received 300 kg N ha −1 produced 10% higher dry matter yield than those that received 150 kg N ha −1 in 2004. Plants that underwent nitrogen application methods 1 and 2 produced 21% and 23% higher dry matter yield of first crop than plants that underwent method 3, respectively. The increase in number of tillers per meter in the 300 kg N ha −1 treatment and in nitrogen application methods 1 and 2 resulted in the higher dry matter yields of first crop in these treatments. For the second crop, plants that received 300 kg N ha −1 produced 10% higher dry matter yield of second crop than those that received 150 kg N ha −1. Plants that underwent nitrogen application methods 2 and 3 produced 57% and 56% higher dry matter yield of second crop than method 1, respectively. The increase in number of tillers per meter in the 300 kg N ha −1 treatment and in nitrogen application methods 2 and 3 resulted in the higher dry matter yields of second crop in these treatments. Overall, plants that received 300 kg N ha −1 produced 7% higher dry matter yield than those that received 150 kg N ha −1 and plants that underwent nitrogen application method 2 produced 21% and 11% higher dry matter yield than those that underwent methods 1 and 3, respectively. Therefore, our findings suggest that to produce the highest total dry matter yield the best time for first harvest is the full heading stage and the best nitrogen management is to provide 300 kg N ha −1 in accordance with nitrogen application method 2.