Abstract
ABSTRACT To achieve an accurate phenotyping for drought tolerance, it is important to control water stress levels and timing. This study aimed to determine water use by upland rice plants during periods of irrigation withholding and its relationship with grain yield in order to increase the efficiency of this phenotyping. Two experiments were carried out in a randomized block design in which six water treatments (irrigation withholding for periods of 2, 4, 6, 8, 10 and 12 days) were compared, with four replicates. In the first experiment, treatments were applied at the R3 stage (panicle exsertion) and, in the second, at the R5 stage (beginning of grain filling). The amount of water evapotranspired was determined by the difference between the soil water storage at the beginning and at the end of irrigation withholding periods, from the surface to 80-cm depth. Evapotranspiration of upland rice from R3 stage was higher compared to that observed from R5 stage, when subjected to similar irrigation withholding periods in both growth stages. Rice grain yield is more sensitive to irrigation withholding imposed from R5 stage than from R3 stage.
Highlights
Most of the Brazilian upland rice production occurs in the Cerrado region, where soils are characterized by having low water-storage capacity, low natural fertility and elevated acidity, factors that limit grain yield of crops other than rice
It was observed that the use of the water stored in the soil surface layer, 0-20 cm depth, during the periods of irrigation withholding was described by an exponential equation in the R3 stage
Regarding the use of soil water by plants during the R5 stage, in 0-20 cm soil layer, water depletion occurred with the increase in the number of days without irrigation, as in R3 stage
Summary
Most of the Brazilian upland rice production occurs in the Cerrado region, where soils are characterized by having low water-storage capacity, low natural fertility and elevated acidity, factors that limit grain yield of crops other than rice. Rice tolerates these soil limitations, allowing the exploitation of large areas (Guimarães et al, 2013). The objectives of the study were to determine water use by plants during periods of withholding irrigation and its relationship with grain yield to increase the efficiency of rice phenotyping for the conditions of water stress. The water storage was calculated by layers of 20 cm from the surface to 80-cm depth, by multiplying the gravimetric moisture by the bulk density and
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