Prediction of N availability and rice yield in lowland soils: nitrogen mineralization parameters
1992
Manguiat, I.J. | Mascarina, G.B. (International Rice Research Inst., Los Banos, Laguna (Philippines))
Field experiments with parallel laboratory incubation tests were conducted under flooded conditions using Maahas clay amended with urea and rice straw-sesbania mixtures during the wet and dry seasons. The general objective of the study was to generate models for improving the prediction of N availability and rice yield in lowland soils. Results indicate that N mineralization patterns of flooded soils amended with urea and rice straw-sesbania mixtures followed a logistic model. Mineralization potential (No) was positively correlated with extractable (NH4 + after 112-day laboratory incubations and was negatively correlated with mineralization rate constant. No was positively correlated with N uptake and grain yield. N availability based on N uptake in an unfertilized soil predicted from the regression model overestimated the N availability based on actual N uptake in the control plot by about 12%. Extractable N in the field correlated positively with extractable N in the laboratory at 14 days after transplanting. The extractable N from laboratory incubations was also highly correlated with grain yield at all growth stages. These findings should enable researchers to improve the reliability of predicting N supply to lowland rice
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