Yield trends, soil fertility changes and indigenous nitrogen supply as affected by crop and soil managementin intensive irrigated rice systems
2004
Nguyen, H.T.
Results from four long-term experiments in India, Vietnam, Indonesia, and China with N,P,K omission and full NPK fertilization, show after 4-7 years of intensive rice cultivation, decreased soil available P and K in P and K omission treatments, respectively, but not in full NPK treatment at most sites. There was no yield decline in all treatments at most sites. Four water treatments (continuous flooding, soil drying, and aerobic tillage, soil drying and wetting) and two residue treatments (residue removed and residue returned) were applied between rice crops in short-term experiment at IRRI [International Rice Research Institute], Los Baños, Laguna, Philippines]. The interactions between water regimes and residue management were significant. Soil drying and aerobic tillage gave the highest soil ammonium availability, crop growth and yield, N uptake and indigenous N supply with residue removed. Continuous flooding had the best performance with r esidue returned. Alternate drying and wetting gave the lowest performance. The results from assessment of indigenous N supply by simulation shows DNDC model lacks predicted ability for nitrate build-up, N immobilization and N flush as affected by crop and soil management between rice crops, and it did not effectively predict indigenous N supply over long term.
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