Sustainability of varied crop sequences, with special reference to nutrient utilization
2001
Pascua, S.R. Jr | Valencia, D.A. (Mariano Marcos State Univ., Batac 2906, Ilocos Norte (Philippines). Rainfed Lowland Rice Research Consortium) Padre, A.T. | Marcos, T.F. | Obien, S.R. | Reichardt, W.
A long-term field trial (1991-2000) was conducted in Batac, Ilocos Norte in an isohyperthermic udic eutropept clay loam to determine the effects of intensified cropping and fertilizer application on the nutrient status of the soil and on crop yield, and to find out the influence of crop residue addition on the yield of rice. There were 5 levels of N applied to rice (0, 30, 60, 90, 120 kg/ha) and 5 cropping systems (rice-corn-mungbean, rice-mungbean-corn, rice-garlic-mungbean, rice-sweet pepper-corn and rice-tomato-corn) with and without the recommended rates of fertilizer for each main dry season (DS) crop. The yield at 90 kg N/ha was 3.88 t/ha; at 120 kg N/ha it was 4.28 t/ha. A change of variety from BPI Ri10 to PSB Rc14 increased yields ranging from 1.7 to 2.1 t/ha regardless of N applied. Crop residue added increased rice grain yield from 0.4 to 0.6 t/ha specifically for fertilized DS crops. Fertilizer applied to the main DS crop had a residual effect, increasing rice grain yield from 0.4 to 0.9 t/ha in the rice-sweet pepper-corn, rice-tomato-corn and rice-garlic-mungbean systems. DS crops with the recommended rate of fertilizer applied produced significantly higher yields except mungbean. Furthermore, fertilized plots with glutinous green corn produced from 0.14 to 5.31 t/ha when planted as relay to sweet pepper, and 0.54 to 4.42 t/ha as relay to tomato. Plots applied with the recommended fertilizer rates showed higher soil N than the unfertilized plots during the 1997 and 1999 samplings. Rice-corn-mungbean had a higher soil N, 0.113%, than rice-mungbean-corn, 0.104%. In 1999, plots applied with the recommended rates of fertilizer showed higher C content, 1.39%, than the unfertilized plot, 1.35%. The rice-garlic-mungbean system contributed significantly to buildup of extractable K in the soil due to the rice straw incorporated as mulch, which weighed about 10.1 t/ha, with mean equivalent K value of 258 kg/ha/year or 10 bags of KCI
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