Produtividade da água de arroz de terras baixas irrigado por aspersão

Abstract

The objective of this work was to evaluate the irrigation water and total water productivity for different lowland rice cultivars irrigated by sprinkling. The study was carried out in the agricultural years 2010/2011, 2014/2015, 2015/2016 in a completely randomized block design with subdivided plots and randomized blocks in 2016/2017. In 2010/2011, 2014/2015 and 2015/2016 treatments were lowland rice cultivars grown under five sprinkler irrigation layers (0, 50, 100, 150 and 200% of the crop evapotranspiration, ETc) with four replications. In 2016/2017, the experimental design was maintained, but the 0% ETc depth was removed and the 250% ETc irrigation depht was added. The need for irrigation was determined from the crop evapotranspiration (ETc), multiplying the reference evapotranspiration (ETo) by the crop coefficient (Kc). The water input (I) (m³ ha-¹) was measured from the sum of the irrigations for each sprinkler irrigation depth. The Total Water (WT) (m³ ha-¹), was measured by the sum of the irrigation volume plus the rainfall recorded during the entire crop development cycle. The Irrigation Water Productivity (WPi) (kg m-³), as the relationship between grain yield (13% humidity) and water input. Total Water Productivity (WPt) (kg m-³) was calculated as the relationship between grain yield and total water volume (irrigation + rainfall). In all agricultural years there was no interaction between sprinkler irrigation depths and cultivars for WPi and WPt, showing a significant difference between sprinkler irrigation depths and between lowland rice cultivars. The highest water input was observed in the 2014/2015 agricultural year with a total volume of 3003.10 m³ ha-¹. The highest value for WPi was observed in the 209% depth of ETc, with WPi of 3,389 kg m-³. For WPt the highest value observed was in the irrigation sprinkler of 156.76% of ETc, with WPt of 0.806 kg m-³. Among the genetic materials used, the lowland rice hybrid XP 102 CL showed the highest values for WPi and WPt in the different agricultural years of this study. The average of the irrigation depths to find the highest values of WPi and WPt for the four agricultural years of study are 163.80 and 176.21% of ETc, respectively.