Sustainability of diverse lowland rice-based cropping systems with special reference to nutrient utilization
1997
Pascua, S.R. Jr. | Ladha, J.K. | Agustin, E.O. | Ventura, W. | Valencia, D.A. | Marcos, T.F. | Sta Cruz, P.C. | Obien, S.R. (Mariano Marcos State Univ., Batac, Ilocos Norte (Philippines))
A long-term experiment was started in 1991 at Mariano Marcos Staate Univ. (MMSU), Batac, Ilocos Norte [Philippines] to determine the interaction of rainfed lowland rice with the dry season (DS) crops in various cropping systems especially in terms of nutrient availability and utilization. The DS crops studied were garlic, corn, sweet pepper, and mungbean. Starting in 1994, glutinous corn was relayed to tomato, sweetpepper and mungbean and harvested as green corn while mungbean was relayed to garlic and planted after corn harvest. With low initial total soil N (0.11 percent), available soil Olsen P (5.83 mg/kg) and exchangeable K (0.84 me/100 g), mean rice yield (1991-1993) without N fertilizer applied was 1.1 t/ha, 2.5 t/ha when applied with 120 kg N/ha. Incorporation of crop residues started in 1993 WS. An increased mean rice yield (1994-1996) of 2.4 t/ha and 4.6 t/ha was produced when not applied with N fertilizer and when applied with 120 kg N/ha, respectively. The NPK balance showed that large amount of the added N fertilizer was not utilized by the rice crop, but this residual N had little effect on the succeeding DS crops. Except mungbean, all other crops required the recommended fertilizer rate for higher yield. The yields of relayed crops were significantly affected by the fertilizer input of the main DS crops. Although the NPK balance showed large amount of N left in soil, large losses occured such that the DS residual fertilizer effect was significant but low to the next WS rice. The advantage of the relay crop in catching the residual nitrate N was indicated
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