(19(3):26-41)STUDIES ON THE TECHNIQUES OF NITROGEN FERTILIZATION OF RICE PLANTS (PART 1) EFFECT OF THE LATE TOP-DRESSING OF NITROGEN ON THE YIELD AND NUTRIENT UPTAKE OF RICE PLANTS

使用兩個水稻品種，新竹56號及矮腳尖於羅東、桃園、樹林三處不同土壤進行田間肥料試驗，探求水稻氮素營養與產量之關係而闡明氮肥之晚期施用效果。此氮肥之晚施處理為全部之氮肥用量之百分之六十做為基肥及第一次追肥另百分之四十施用於水稻幼穗形成期以後即生殖生長期中施用。本試驗使用兩品種，三處試驗地，57年第一期作及第二期作，即共有十二個之田間試驗所得之結果如下： 1.同量氮肥N100公斤/公頃施用之下，晚施區比較對照區之慣行施肥可得稻谷增產4%。多氮配合晚施即N120公斤/公頃時可得6%增產，而N140公斤/公頃時可得9%增產。使用晚期施肥技術可能提高原來之氮肥施用適量而得增產。 2.兩品種對多氮晚施都表現顯著的稻谷增產效果。第一期作新竹56號得增產12%，矮腳尖6%，但第二期作新竹56號6%，矮腳尖11％。平均稻谷產量兩品種間差異甚微，即新竹56號5.00公噸/公頃，矮腳尖4.93公噸/公頃。 3.同量氮肥N140公斤/公頃施用之下，比較硫安與尿素之效果時，硫安區之谷產量為5.22公噸/公頃，尿素區為5.11公噸/公頃，相差2%。 4.同量氮肥N100公斤/公頃施用之下，比較硫銨與磷銨系複合肥料（日製15-15-10）及尿素系複合肥料（臺製16-8-12）之肥效，其稻谷產量指數硫安為100時，磷銨系複合肥料102，尿素複合肥料97。 5.稻谷產量高的氮肥晚施區之水稻在生育前期之稻竟濃度比對照區者為低，但生育後期變高。氮肥晚施方法，使水稻在營養生長與生殖生長之中問降低氮濃度，即引起氮缺乏，而生殖生長期問中，一直保持氮高濃度。此種水稻氮營養狀態，似可得稻谷增產。 6.氮肥之晚施及多施使水稻氮吸收量增加之外，藁谷鉀濃度亦增加，即促進水稻對鉀的吸收。 7.矮腳尖對三要素之吸收比新竹56號為強，尤其矮腳尖稻谷之氮含量較高，即蛋白質含量較高。 Two rice varieties, Hsinchu 56, Japonica type and Aichiawchien, Indica type, were used in the field fertilizer experiments at three sites, Lotung sate alluvial soil, Taoyunan latosol, Shulin sandstone shale alluvial soil, in order to investigate the relationship between the plant nitrogen status and the yield of rice. Sepcial emphasis was laid on the effect of the late top-dressing of nitrogen that is 40% of total amount of nitrogen was applied after the stage of the panicle primodial formation. The results obtained from twelve experiments including two varieties, three sites, two crops were as follows: 1.The grain yield of the nitrogen late top-dressing plot was increased 4% as compared with that of the control plot under the same amount of nitrogen application, N 100 kg/ha. The grain increment of the late top-dressing was 6% ant N 120 kg/ha plot and 9% at N 140 kg/ha plot. The optimum nitrogen requirement will be increased and the better yield will be obtained if the nitrogen late top-dressing method is used in paddy fields. 2.Significant effectiveness of the high nitrogen late top-dressing on grain yield was observed for both varieties. In the first crop, 12% of grain increment was obtained for Hsinchu 56 and 6% for Aichiawchien, while in the second crop, 6% for Hsinchu 56 and 11% for Aichiawchien. The averagegrain yield of the two varieties was quite close, that in 5.00 ton/ha for Hsinchu 56 and 4.93 ton/ha for Aichiawchien. 3.In comparison of ammonium sulfate and urea under the N 140 kg/ha application, the grain yield of the ammonium sulfate plot was 5.22 ton/ha while that of the urea plot was 5.11 ton/ha showing 2% difference in grain yield. 4.Taking the grain yield of ammonium slufate as 100 under the same amount of nitrogen N 100 kg/ha application, that of the compound fertilizer of ammonium phosphate type (grade 15-15-10) was 102 and the compound fertilizer of urea type (grade 16-8-12) was 97. 5.The nitrogen content of rice straw of the high nitrogen late top-dressing plot which hand the highest yield was lower at the early growing stage, however, the nitrogen content became higher at the later growing stage as compared with that of the control plot. The late top-pressing method induced the lower nitrogen content of straw showing nitrogen deficient status at the middle stage of rice growing period, and after that the nitrogen content became higher than that of the control plants through reproductive stage. This nitrogen status seems to be better for rice to produce higher yield. 6.The nitrogen late top-dressing or high nitrogen application had rice plants increase nitrogen content as well as potassium content. The increase of nitrogen absorption seemed to promote potassium absorption. 7.More absorption of three elements by Aichiawchien than by Hsinchu 56 was observed. Higher nitrogen content, presumably higher protein content, was found especially in grains of Aichiawchien