Cassman, K. G. and et al, . (1998) Opportunities for increased nitrogen-use efficiency from improved resource management in irrigated rice systems. Field Crops Research, 56 (1-2). pp. 7-39.
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Abstract
Research and extension work to improve nitrogen (N) management of irrigated rice has received considerable investment because yield levels presently achieved by Asian farmers depend on large amounts of N fertilizer. Most work has focused on placement, form, and timing of applied N to reduce losses from volatilization and denitrification. In contrast, less emphasis has been given to development of methods to adjust N rates in relation to the amount of N supplied by indigenous soil resources. As a result, N fertilizer recommendations are typically made for districts or regions with the implicit assumption that soil N supply is relatively uniform within these domains. Recent studies, however, document tremendous variation in soil N supply among lowland rice fields with similar soil types or in the same field over time. Despite these differences, rice farmers do not adjust applied N rates to account for the wide range in soil N supply, and the resulting imbalance contributes to low N-use efficiency. A model for calculating N-use efficiency is proposed that explicitly accounts for contributions from both indigenous and applied N to plant uptake and yield. We argue that increased N-use efficiency will depend on field-specific N management tactics that are responsive to soil N supply and plant N status. N fertilizer losses are thus considered a symptom of incongruence between N supply and crop demand rather than a driving force of N efficiency. Recent knowledge of process controls on N cycling, microbial populations, and soil organic matter (SOM) formation and decomposition in flooded soils are discussed in relation to N-use efficiency. We conclude that the intrinsic capacity of wetland rice systems to conserve N and the rapid N uptake potential of the rice plant provide opportunities for significant increases in N efficiency by improved management and monitoring of indigenous N resources, straw residues, plant N status, and N fertilizer
| Item Type: | Article |
|---|---|
| Author Affiliation: | Agronomy Department, 279 Plant Science Building, University of Nebraska, Lincoln, NE 68583-0915, USA |
| Subjects: | Plant Protection Statistics and Experimentation > Experimentation Crop Improvement |
| Divisions: | Other Crops |
| Depositing User: | Mr. SanatKumar Behera |
| Date Deposited: | 05 Mar 2012 03:01 |
| Last Modified: | 05 Mar 2012 03:01 |
| Official URL: | http://dx.doi.org/10.1016/S0378-4290(97)00140-8 |
| URI: | http://eprints.icrisat.ac.in/id/eprint/3067 |
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