Abstract
ABSTRACT Due to the sensitivity of the cowpea to water deficit during the dry season in the Amazonian environment, there is a need for studies related to water management and the optimization of annual yield. Thus, the objective was to estimate the crop evapotranspiration (ETc) and the actual evapotranspiration (ETr), whilst also evaluating the effect of different irrigation depths on the yield response factor (Ky) and dry biomass (Kss) of the cowpea cultivar BR3-Tracuateua under edaphoclimatic conditions in the Amazon region. The experiment was carried out in randomized blocks, with six replicates and four treatments: T1 (100% ETc), T2 (50% ETc), T3 (25% ETc), and T4 (0% ETc), commencing in the reproductive phase with a drip irrigation system. The total evapotranspiration recorded for the cowpea cultivar BR3-Tracuateua across the four treatments was 337.5, 284.35, 258.62, and 219.82 mm with an average consumption of 4.6, 3.90, 3.54, and 3.01 mm d-1 for T1, T2, T3, and T4, respectively. The emergence phase showed evaporation rate of 5.19 mm d-1 and the reproductive, vegetative, and senescence ETc phases showed evaporation of 4.87, 4.84, and 3.32 mm d-1, respectively. The flowering stage had the greatest water demand (5.88 mm d-1). There was a significant difference in the crop yield among all treatments, with decreases of 18.91, 33.12 and 57.17% for T2, T3 and T4 in the grain yield, with a Ky of 1.48, and Kss of 2.03, 1.08, and 0.87 for the flowering, grain filling, and physiological maturation stages, respectively.
Highlights
Grain yield is affected by the duration and time of occurrence of the water deficit, with the knowledge of water demand in the phenological stages being a fundamental need for efficient irrigation (Azevedo et al, 2011)
It is necessary to quantify the evapotranspiration and define the response factors of the crop to water deficit (Ky), which helps us to understand the phenological stage that is most sensitive to water stress (Doorenbos & Kassam, 1994; Keffer et al, 2019; Patanè & Saita, 2015)
There are no estimates in the FAO 33 for the Ky/Kss for cowpea; estimates are only provided for common beans (Phaseolus vulgaris) that are highly sensitive to water deficit (Ky = 1.15) (Doorenbos & Kassam, 1994; Patanè et al, 2011)
Summary
Grain yield is affected by the duration and time of occurrence of the water deficit, with the knowledge of water demand in the phenological stages being a fundamental need for efficient irrigation (Azevedo et al, 2011). It is necessary to quantify the evapotranspiration and define the response factors of the crop to water deficit (Ky), which helps us to understand the phenological stage that is most sensitive to water stress (Doorenbos & Kassam, 1994; Keffer et al, 2019; Patanè & Saita, 2015). There are no estimates in the FAO 33 for the Ky/Kss for cowpea; estimates are only provided for common beans (Phaseolus vulgaris) that are highly sensitive to water deficit (Ky = 1.15) (Doorenbos & Kassam, 1994; Patanè et al, 2011). Technical studies during periods of lower rainfall and on the effects of irrigation on crop productivity are necessary to increase productivity in the region
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