Nitrogen uptake and recovery from urea and green manure in lowland rice measured by15N and non-isotope techniques |
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Authors: | K H Diekmann S K De Datta J C G Ottow |
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Institution: | (1) Agronomy-Physiology-Agroecology Division, The International Rice Research Institute, Los Baños, P.O. Box 933, Manila, Philippines;(2) Institute of Microbiology and Agronomy, Justus-Liebig University, DW-6300 Giessen, Germany;(3) International Research and Development, Crop and Soil Environmental Sciences, Virginia Polytechnic Institute and State University, 1060 Litton Reaves Hall, 24061-0334 Blacksburg, VA, USA |
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Abstract: | In the recent past considerable attention is paid to minimize dependence on purchased inputs such as inorganic nitrogen fertilizer. Green manure in the form of flood-tolerant, stem-nodulatingSesbania rostrata andAeschynomene afraspera is an alternative N source for rice, which may also increase N use efficiency. Therefore research was conducted to determine the fate of N applied to lowland rice (Oryza sativa L.) in the form ofSesbania rostrata andAeschynomene afraspera green manure and urea in two field experiments using15N labeled materials.15N in the soil and rice plant was determined, and15N balances established. Apparent N recoveries were determined by non-tracer method.
15N recoveries averaged 90 and 65% of N applied for green manure and urea treatments, respectively. High partial pressures of NH3 in the floodwater, and high pH probably resulted from urea application and favoured losses of N from the urea treatment. Results show that green manure N can supply a substantial proportion of the N requirements of lowland rice. Nitrogen released fromSesbania rostrata andAeschynomene afraspera green manure was in synchrony with the demand of the rice plant. The effect of combined application of green manure and urea on N losses from urea fertilizer were also investigated. Green manure reduced the N losses from15N labeled urea possibly due to a reduction in pH of the floodwater. Positive added N interactions (ANIs) were observed. At harvest, an average of 45 and 25% of N applied remained in the soil for green manure and urea, respectively.Contribution from IRRI, Los Baños, Philippines and Justus-Liebig-University, Giessen, GermanyContribution from IRRI, Los Baños, Philippines and Justus-Liebig-University, Giessen, Germany |
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Keywords: | Aeschynomene afraspera green manure lowland rice 15N balance Sesbania rostrata |
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