Comparison of Different Methods of Rice Establishment and Nitrogen Management Strategies for Lowland Rice

摘要

Shortage of labor and water are forcing farmers to explore the alternatives of transplanting. A field experiment was conducted at the experimental farm of International Rice Research Institute (IRRI), Philippines during the 2003 wet season and the 2004 dry season to (1) evaluate the effects of different crop-establishment methods and N management on yield and yield parameters of rice; (2) determine N-use efficiency and water-use efficiency under different methods of rice establishment; and (3) analyze the economics of different crop-establishment methods. Crop-establishment method did not influence grain yield during the wet or dry seasons, indicating the potential of the three variants of direct seeding as alternative methods of establishing lowland rice. Direct-seeded rice had shorter crop duration, required less water and therefore had higher water-use efficiency than the transplanting method. Crop establishment did not influence the various indices of nitrogen-utilization efficiency except partial factor productivity of N (PFP_N) during the wet season. During the dry season, dry-seeded rice had the lowest recovery efficiency. In contrast, agronomic-use efficiency and recovery efficiency were significantly higher in the SPAD-based (soil plant analyses development) N management strategy during the dry season. PFP_N was significantly higher in the SPAD-based N management strategy during the wet and dry seasons. The interaction effect of crop establishment and N management indicated that for smaller N input and higher efficiency of N usage, N requirement for direct-seeded rice should be based on SPAD N technique. The cost-and-return analysis showed that benefit-cost ratio was consistently higher in dry seeding rice than transplanted rice using aSPAD-based N management.