Contribution of rice tillers to dry matter accumulation and yield
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A rice (Oryza sativa L.) crop functions as a population of tillers produced at different times and possessing specific growth characteristics. The objective of this study was to characterize the contribution of cultivar tillering ability to dry matter accumulation, yield components, and grain yield. Field experiments were conducted over a 2-yr period using a completely randomized plot design at Beaumont, TX, grown under a pin-point flood system, with a China clay soil (fine, smectitic, hyperthermic Oxyaquic Dystrudert). Three cultivars were chosen (Gulfmont, Rosemont, and Teqing), to represent moderate to high tillering abilities, and three plant densities were chosen (56, 112, and 169 plants m-2), to produce differential competition for light and nutrients. Teqing had the highest tillering ability and partitioned more mass to tillers, especially at the lowest plant density, with 77% of the total mass represented by tillers, compared with 71 and 69% for Gulfmont and Rosemont, respectively. However, total dry mass per unit area at harvest was not significantly different, contrasting the plant density treatments (1618, 1725, and 1744 g m-2 for the 56, 112, and 169 plants m-2 treatments, respectively, when averaged across cultivars). Both cultivar and plant density significantly affected a number of yield components, but not kernel weight. The higher yield of Teqing (918 g m-2), contrasted with the lower-yielding Gulfmont (791 g m-2) and Rosemont (729 g m-2), appears largely to have resulted from its greater tillering ability, higher spikelet density, and longer maturation period, which makes greater use of the relatively long growing season length at Beaumont.