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Agronomic and Physiological Responses of Hybrid Rice to Seed Recycling, Nitrogen Level, and Biodynamic Practices
Dissertation Abstract:
Field experiments were conducted at the University of the Philippines Los Baños in 2005 and 2006 to evaluate the agronomic and physiological performance of the F1 and F2 generations of PSB Rc 72H (dry season only), NSIC Rc 114H, and NSIC Rc 116H under different nitrogen (N) levels during the dry and wet seasons. An inbred (Burdagol) and two generations of PSB Rc 72H were evaluated during the wet season using zero-N, 50, and 100 kg N ha-1. Biodynamic (BD) preparations were applied to the zero-N plots.
Nitrogen level did not affect most agronomic parameters except grain yield, which was significantly higher under the recommended N level during the dry and wet seasons. Grain yield in the 0 N + biodynamic plots was significantly lower than the yield from the N-fertilized plots. Grain yield obtained from 0 N + BD plots, however, was relatively high (3.88 t ha-1). PSB Rc 72H had the highest grain yield whereas NSIC Rc 114H had the lowest. Regardless of N level, the F2 generations had significantly lower yield than the F1 hybrids by 11-25 percent during the dry season. The grain yield of the F2 generations of PSB Rc 72H and NSIC Rc 114H was statistically similar to the yield of the F1 hybrids during the wet season. The number of panicles m-2 was the sole yield parameter significantly related to the grain yield of the F2 generations during the dry season whereas the number of filled spikelets m-2 and harvest index were significantly related to grain yield during the wet season. These yield parameters in addition to loss of uniformity in flowering, height, and panicle length accounted for the yield depression. Hybrids with higher yield potential were more prone to yield depression than those with lower yield potential. Physiological responses to N level and biodynamic practices generally did not vary with variety generation.
Seed recycling is variety- and season-specific. The study recommended to recycle a segregating generation if the savings on cost of seeds is greater than forgone net returns. Long-term studies are needed to evaluate further the effectiveness of biodynamic practices on lowland rice.