著者

Ando Ho Kakuda Ken-ichi Nakayama Munetaka YOKOTO Kei-ichi

出版者

一般社団法人日本土壌肥料学会

雑誌

Soil science and plant nutrition (ISSN:00380768)

巻号頁・発行日

vol.46, no.1, pp.105-115, 2000-03-01

被引用文献数

2

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Due to high the labor cost, direct seeding is being gradually applied for crop establishment throughout Asia. Recently, the development of the so-called, "controlled release fertilizers" (CRFs) which requires only "one shot dose" of N, has enabled to reduce the cost of labor for the application of topdressed N. Thus, in order to limit pollution and cost, no-tillage direct-seeded lowland rice cultivation accompanied by the use of CRF is being recommended. To evaluate the effects of CRFs on the growth and yield of no-tillage direct-seeded rice, a field experiment was carried out in the north-eastern region of Japan in 1993 and 1994. Five N treatments were used: (1) ammonium sulfate (AS) band placement application with seeds at the time of seeding (AS1); (2) AS broadcast application after irrigation (AS2); (3) CRF (LP100) co-situs application at the time of seeding (L1); (4) CRF (LPS100) co-situs application at the time of seeding (L2); and (5) minus N (MN). The rate of basal N was 60 kg N ha^<-1>. Topdressed N in the AS1 and AS2 treatments was applied at 25 d before heading at the rate of 20 kg N ha^<-1>. The highest yield was obtained in the L1 treatment in both years. The number of grains per unit area was affected by the amount of N in the plants at heading. The percentage of filled grains in the L2 treatment was the lowest by about 15 to 20% among the treatments. The recovery percentages of basal N on July 20 were about 20 to 30% in the AS1, AS2, and L1 treatments, and only about 14% in the L2 treatment. About 75 to 80% of basal N was absorbed by the plants at harvest in the L1 and L2 treatments. On the other hand, the plants had absorbed only about 25 to 30% of the applied basal N in the AS1 and AS2 treatments at harvest. There was no difference in the N-recovery percentage (based on the amount of released N) between the L1 and L2 treatments. Nitrogen-use efficiency was not significantly different among the treatments. However, higher N-use efficiency was obtained in this experiment than in early studies in the tropics. The agronomic efficiency of CRFs was higher than that of ammonium sulfate.