Direct underground sowing culture of rice in flooded paddy field in the area of early season culture: Methods of nitrogen fertilization for rice plants directly sown in flooded fields
1990
Komatsuka, T. (Chiba-ken. Horticultural Experiment Station, Tateyama (Japan)) | Saito, K. | Nagashima, T. | Katsukita, H. | Ota, T.
Methods of nitrogen fertilization for rice plants sown directly undergrown in flooded fields were studied for the following three rice varieties differing in the plant type and the fertilizer responsiveness: Koshihikari (medium type; highly lodging-susceptible), Hayahikari (panicle weight type; highly lodging-resistant), and Hatsuboshi (panicle umber type; lodging-resistant). The following results were obtained: 1) Direct-sown rice plants had longer culms and were more susceptible to lodging than the transplanted rice, even when the basal nitrogen application had been reduced by 30%. Combination of the basal dressing and topdressing at the tilling stage was effective for securing the panicle number, while it resulted in longer culms and severer lodging of the rice plants. The amount of applied nitrogen being the same, the panicle number depended on the number of plant establishment. 2) For the direct-sown Koshihikari with 20 kg/ha of basal nitrogen application the rice yield was 4.8 t/ha which was lower than that for the transplanted counterpart. For the direct-sown Hayahikari, a yield of 5.5 t/ha was attained when 60 kg/ha of nitrogen was applied as the basal dressing. However, the yield was variable among the years. On the contrary, a higher and more stable yield of 5.5-6.0 t/ha was obtained for the direct-sown Hatsuboshi. The yield was comparable to that of the transplanted ones, and the variety was found to be the most suitable one to the direct sowing among the three varieties tested. The optimal amount of nitrogen application depended on the number of plant establishment; topdressing at the tillering stage, in addition to the basal nitrogen application of 40 kg/ha, resulted in a better yield only when the number of the establishment was smaller
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