Reduced cost soil fertility management for rice in irrigated rice-based cropping systems in Central Luzon [Philippines]
1989
Gines, H.C. | Maranan, C.G. | Morris, R.A. | Pandey, R.K. | Garrity, D.P. (International Rice Research Inst., Los Banos, Laguna (Philippines))
Farmers at the pump irrigated key research site at Guimba, Nueva Ecija [Philippines] are now observed to apply excessive N levels to their rice crop (72-180 kg/ha) compared to the researchers derived maximum net profit level for N application (56-80 kg N/ha). Data from cropping pattern trials for three crop years indicated that farmers apply 56 and 36% more N in the upper stratum (Turod) and lower stratum (Lungog) landforms, respectively than the profits maximizing levels. Greater response to N was observed in the Turod than in the Lungog possibly due to higher soil OM [organic matter] content in the latter. Irrigated rice in both landforms showed no significant response to P and K. Partial budgeting was used to determine the most profitable level of fertilizer application. In the turod, yield was highest at 90-30-30 but net benefit was highest at 60-0-0 NPK level. In the lungog, yield was highest at 60-30-30 but net benefit was highest at 60-0-0. In both landforms, there were only three undominated treatments, i.e., treatments with lower cost but higher net benefits (0-0-0, 30-0-0 amd 60-0-0). Marginal analysis of the undominated response data over three years showed highest marginal rate of return at 60-0-0 in the turod and 30-0-0 in the lungog. Green manure studies indicated the potential of pre-rice Sesbania rostrata as a source of organic N that will substitute for the entire N requirement of the wet season [WS] rice crop. It can be relay-seeded into the WS rice crop as early as 21 days before harvest to be incorporated as green manure supplying 60 kg N/ha for transition season rice crop.
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