Drought stress index for rice
1988
Yambao, E.B. | Ingram, K.T. (International Rice Research Inst., Los Banos, Laguna (Philippines). Dept. of Agronomy)
A drought stress index maybe used to assess the levels of drought in different drought screening trials to enable comparison of results among trials in different locations and years. A greenhouse experiment was conducted to develop a drought stress index for rice (Oryza sativa L.), which relates water deficit at various durations and developmental stages to growth, yield, and transpiration. IR64 was grown in pots in a greenhouse under aerobic soil conditions. Water was withheld for 5, 10, or 15 days from stress treatment pots beginning at 10, 25, 40, 55, 70, 85 and 100 days after seeding (DAS). Water deficit during the vegetative stage had no significant effect on grain yield. Five and 10-day stresses during the reproductive phase, 45-80 DAS, caused 25-40% yield reduction. At panicle initiation (50 DAS), flowering (70 DAS), and early grain filling (85 DAS) a 15-day stress reduced yields by 70, 88, and 52%. Cumulative difference between transpiration of control and stressed plants, Sigma (Tc-Ts) was lowest during the seedling stage (10-25 DAS) and near harvest (100-110 DAS), and highest from booting to anthesis. Grain yield was inversely related to Sigma (Tc-Ts) (r2=0.72** ), and the relationship appeared to be independent of growth stage. When the ratio of cumulative transpiration of stress to control plants, (Sigma Ts)/(Sigma Tc), was below 0.7, it was directly related to grain yield (r2=0.72** ). It was proposed that Sigma (Tc-Ts) maybe used as a crop-based drought stress index for rice.
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