Rice Yield Components under Water Stress Imposed at Different Growth Stages

Abstract

We aimed to assess rice yield components as function of water stress imposed at distinct crop growth stages under greenhouse, in randomized block design under factorial scheme 3 × 4 + 1, with four replications. The factor "A" was the growth stage in which water stress was imposed, being (a) vegetative, (b) reproductive 1, and (c) reproductive 2; factor "B" was four levels of water stress (0-200 kPa). There was also an additional treatment consisting of a flooded check. Water was replenished to saturation every time the threshold stress was reached. At the end of the cycle, all panicles were counted and collected, per plant, for further analysis. In the lab, grains per panicle were counted, being classified either as whole kernel or aborted grains, whose results were used for obtaining sterility percentage. Whole kernel grains were weighted for obtaining the 1000 grains weight for each treatment, and the consequent plant grain yields. Number of panicles was not affected when stress was imposed after panicle initiation, but when imposed at tillering it was reduced; at grain filling, water stress promoted grains sterility higher than 90%; grain weight was only reduced when carbohydrates were directed to root formation in detriment of grain filling; lower rice grain yield per plant was observed even when treatments were maintained above 10kPa all along the cycle, compared to the flooded treatment.

Actual evapotranspiration and crop coefficients of irrigated lowland rice (Oryza sativa L.) under semiarid climate

“…Ground water table at the site is consistently below 3.0 m with site deep percolation rate (saturated infiltration rate) estimated at 2.0 mm d -1 (Haefele et al, 2001;de Vries, 2010;Djaman et al, 2016a). Assuming that the upward flux was negligible because of soil saturation, R is null and ΔW equals zero because of soil saturation due to permanent flooded under lowland basin irrigation conditions from seedling transplanting to crop physiological maturity (de Vries et al, 2010;Pascual and Wang, 2017;Concenço et al, 2018), the equation is reduced to the following form for calculating ETa:…”