Yield potential limitations: factors affecting yield of deepwater rice in relation to new plant type
1993
Mazareno, A.M. | Egdane, J.A. | Laureles, E.V. | Setter, T. (International Rice Research Inst., Los Banos, Laguna (Philippines))
Traditional deepwater rices (DWR) are low yielding (2 tons/ha). Improvement of plant type is important to increase and stabilize yields. Field studies were conducted in 1992 wet season at IRRI [Philippines] to quantify yield differences as affected by number of main stems, primary and nodal tillers. The effects of genotype versus environment were evaluated by comparing growth of DWR cultivar (HTA 60) with high yielding irrigated cultivar (IR72). HTA 60 and IR72, were grown at 20, 40, 80, 160, and 320 plants/sq m in order to vary number of different tiller types. Increasing density of HTA 60 increased yield from 2-5 t/ha, as a result of 2-3 fold increase in leaf area index (LAI) and number of main stems. The LAI and stems/sq m were also highly correlated with yield in IR72. In HTA 60, only 20 and 40 plants/sq m produced nodal tillers which contributed 20 percent of the yield. Plants at high density (HD) had mainly main and primary tillers which yielded more than twice those at low density (LD). However, HD plants had 3-fold lower yield/panicle for main and primary tillers. Main tiller contributed 35 percent of total yield in HD plants. LD plants had more spikelets/panicle than HD plants. There was no significant difference in panicle/straw ratio, filled grain percentage, and plant height in either HTA 60 or IR72 although HD DWR plants elongated faster at the start of flooding. New plant type for DWR may be achieved by increasing the proportion of main stem tillers relative to the proportion of nodal and primary tillers. It would be useful to evaluate this with DWR cultivars with low tillering ability planted at high density
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