Maximum nitrogen uptake rate of irrigated rice in response to nitrogen topdressing
1996
Laza, M.R.C. | Gines, H. | Shaoking Peng | Garcia, F.V. (International Rice Research Inst., P.O. Box 933, 1099 Manila (Philippines). Agronomy, Plant Physiology and Agroecology Div.)
Plant nitrogen (N) content increases with N application in rice, but little is known of the maximum N uptake rate (NUR) immediately after application. Studies were conducted in the 1995 dry season at IRRI and PhilRice [Philippine Rice Research Inst., Munoz, Nueva Ecija, Philippines] using IR72. NUR was determined at 0, 2, 4, 6, 9, and 14 days after application of 50 and 100 kg N/ha at mid-tillering and panicle initiation. A control (no N application) was maintained. Nitrogen uptake increased with N application. A significantly high NUR was obtained at panicle initiation than at mid-tillering. At panicle initiation, NUR at IRRI was 7.0 plus or minus 0.6 kg N/ha per day at 50 kg N/ha application and 9.2 plus or minus 0.5 kg N/ha per day at 100 kg N/ha, whereas at PhilRice, NUR was 9.4 plus or minus 1.5 at 50 and 11.7 plus or minus 1.1 at 100 kg N/ha. Leaf and stem dry matter and N content correspondingly increased with NUR. However, the increase in dry matter was less than the increase in N content. The maximum NUR values for IR72 obtained from these studies are double that of the previous estimate of 4.0 kg N/ha per day. The high uptake rate immediately after N application indicates high N-absorbing capacity of the rice root system
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