Benefits of real-time N fertilizer management during four years in two long term experiments
2004
Samson, M.I. | Laureles, E.V. | Lazaro, W.M.International Rice Research Inst., Los Banos, Laguna (Philippines). Crop, Soil and Water Sciences Div. | Gines, H.C. | Buresh, R.J.
Long-term experiments (LTE) began at the International Rice Research Institute (IRRI) in 1964 and at the Philippine Rice Research Institute (PhilRice) [Munoz, Nueva Ecija, Philippines] in 1968 to assess the effect of intensive double rice cropping on yield, productivity, and sustainability of rice production. The increasing cost of N fertilizer management as a strategy for efficient use of N fertilizer. In real-time N management, the color of the rice leaf is monitored at 7-10-day intervals, and N is applied whenever leaf color is more yellowish green than the critical value on the leaf color chart(LCC). The reseachers report the effects of real-time N management on yield, fertilize use, and rice disease at both locations from 2001 to 2004. Real-time N management in the dry season (DS) reduced N fertilizer use by 45% to 80% compared with a fixed seasonal N rate of 210 kg N/ha, while achieving comparable or higher yileds of 6 to 9 t/ha. The seasonal rate of 210 kg N/ha, which has been used since the early 1990s, was selected to ensure sufficient N to achieve 90/ha, but climate limited attainment of this yield target in nearly all years. Real-time N management in the wet season (WS) resulted in N inputs ranging from 88% to 113% of the fixed seasonal rate of 80 kg N/ha, although similar yields were produced. The agronomic use efficiency of N fertilizer in the DS was 21 to 43 kg increase in grain/kg N fertilizer compared with 12 to 22 kg/kg with the high fixed rate of N fertilizer. In the WS, the agronomic efficiency was 11 to 33 kg/kg versus 1 to 27 kg/kg for the 80 kg N/ha rate. Real-time N fertilizer management can increase N use efficiency and maintain or increase yield.
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