Evapotranspiration, crop coefficient and water use efficiency of onion cultivated under different irrigation depths

Abstract

This study aimed to determine crop evapotranspiration through the soil water balance, the crop coefficient and water use efficiency of the onion (Allium cepa L.) in a system with four irrigation regimes, cultivated in the semiarid region of northeastern Brazil. Two field experiments were carried out during the rainy and dry periods of the region in 2018, using the treatments of 100% (T1), 75% (T2), 50% (T3) and 25% (T4) of the reference evapotranspiration for daily water replacement and five replicates for each treatment. It was verified that crop evapotranspiration varies according to the water availability in the soil; however, the highest water use efficiency occurred for the T3 treatment. The T1 treatment obtained the highest estimated yield, 43.86 tons ha-1, while T4 obtained 13.47 tons ha-1, the lowest estimated yield among the treatments, and this difference was statistically significant (p ≤ 0.05) by F test. The crop coefficients obtained were 0.68, 0.89, 0.99 and 0.73 for the initial, vegetative, bulbing and maturation stages, respectivelyThis study aimed to determine crop evapotranspiration through the soil water balance, the crop coefficient and water use efficiency of the onion (Allium cepa L.) in a system with four irrigation regimes, cultivated in the semiarid region of northeastern Brazil. Two field experiments were carried out during the rainy and dry periods of the region in 2018, using the treatments of 100% (T1), 75% (T2), 50% (T3) and 25% (T4) of the reference evapotranspiration for daily water replacement and five replicates for each treatment. It was verified that crop evapotranspiration varies according to the water availability in the soil; however, the highest water use efficiency occurred for the T3 treatment. The T1 treatment obtained the highest estimated yield, 43.86 tons ha-1, while T4 obtained 13.47 tons ha-1, the lowest estimated yield among the treatments, and this difference was statistically significant (p ≤ 0.05) by F test. The crop coefficients obtained were 0.68, 0.89, 0.99 and 0.73 for the initial, vegetative, bulbing and maturation stages, respectively. Este estudo objetivou determinar a evapotranspiração da cultura através do balanço de água no solo, o coeficiente de cultivo e a eficiência do uso da água da cebola (Allium cepa L.) em um sistema com quatro regimes de irrigação, cultivada no semiárido nordestino. Foram realizados dois experimentos de campo durante os períodos chuvoso e seco da região no ano de 2018, utilizando-se os tratamentos de 100% (T1), 75% (T2), 50% (T3) e 25% (T4) da evapotranspiração de referência para reposição hídrica diária e cinco repetições para cada tratamento. Verificouse que a evapotranspiração da cultura varia de acordo com a disponibilidade hídrica no solo, entretanto, a maior eficiência do uso da água ocorreu para o tratamento T3. O tratamento T1 obteve a maior produtividade estimada em 43.86 tons ha-1 e T4 com 13.47 tons ha-1, a menor produtividade estimada entre os tratamentos. Essa diferença foi estatisticamente significativa (p ≤ 0,05) pelo teste F. Os valores do coeficiente de cultivo obtidos foram de 0,68; 0,89; 0,99 e 0,73 para as fases inicial, vegetativo, bulbificação e maturação, respectivamente.