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.
Highlights
Rice is considered a staple food for approximately half the world’s population, cultivated in about 112 countries, with 90% of the global production concentrated in Asia
Some researchers (Parfitt et al, 2011) report 50% water economy when rice is grown under pivots compared to flooding
The number of tillers per plant was affected by the water stress, but only at the “V” stage (Figure 3), when water tensions of 100 or 200 kPa reduced tillering, respectively, in about 30 and 48%
Summary
Rice is considered a staple food for approximately half the world’s population, cultivated in about 112 countries, with 90% of the global production concentrated in Asia. Water demand in flooded rice is higher than the required for crops traditionally sprinkler irrigated, such as corn or soybeans. This raises some questions regarding water use efficiency and environmental impact caused by rice cultivation. By pivot or linear hardware, continues to be tested for rice cultivation. Some researchers (Parfitt et al, 2011) report 50% water economy when rice is grown under pivots compared to flooding. This is mainly observed when the system is installed in highly sloped areas or in fields with scarce water
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