CONTRIBUTION OF RICE TILLERS TO DRY-MATTER ACCUMULATION AND YIELD

A rice (Oryza sativa L.) crop functions as a population of tillers pro duced at different times and possessing specific growth characteristic s. The objective of this study was to characterize the contribution of cultivar tillering ability to dry matter accumulation, yield componen ts, and grain yield. Field experiments were conducted over a 2-yr peri od using a completely randomized plot design at Beaumont, TX, grown un der a pin-point flood system, with a China clay soil (fine, smectitic, hyperthermic Oxyaquic Dystrudert), Three cultivars were chosen (Gulfm ont, Rosemont, and Teqing), to represent moderate to high tillering ab ilities, and three plant densities were chosen (56, 112, and 169 plant s m(-2)), to produce differential competition for light and nutrients, Teqing had the highest tillering ability and partitioned more mass to tillers, especially tit the lowest plant density, with 77% of the tot al mass represented by tillers, compared with 71 and 69% for Gulfmont and Rosemont, respectively. However, total dry mass per unit area at h arvest was not significantly different, contrasting the plant density treatments (1618, 1725, and 1744 g m(-2) for the 56, 112, and 169 plan ts m(-2) treatments, respectively, when averaged across cultivars). Bo th 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 grea ter tillering ability, higher spikelet density, and longer maturation period, which makes greater use of the relatively long growing season length at Beaumont.