Two evapotranspiration reference estimation methods and water stress index in irrigated onion

Abstract

The objective of this work was to evaluate the effect of two methods to calculate the reference evapotranspiration and the determination of water stress index of the crop on the production of onion bulbs irrigated by sprinkling. The experiment was conducted from April to September 2017, at Santo Antônio site, Monte Alto municipality, São Paulo, Brazil. The experimental design was in blocks with repetitions, consisting of two treatments: T1 and T2, with irrigations based on the reference evapotranspiration by Hargreaves method and Penman-Monteith method, respectively. Each treatment was divided into four blocks for soil water stress measurements and each block with four replicates for measurements of water stress index of the crop. With the results it was concluded that in T1, a higher water volume was applied, but there was no significant difference in productivity. The variability of water stress indices in all blocks was 1.9 ° C to 2.4 ° C, with higher values prevailing in T2, where a lower volume of water was applied. For the whole area, the water stress index at 1.9 ° C corresponded to 50% of the available water capacity in the soil.