Demanda hídrica e eficiência do uso da água em área de coqueiro-anão-verde (cocos nucifera) irrigado em Santa Izabel do Pará, Amazônia oriental.

Abstract

The green dwarf coconut palm (Cocos nucifera L.) has high socioeconomic importance due to the growing demand for coconut water, contributing to the increase of irrigated plantations. However, information that can assist in decision making, planning and irrigation management efficiently is still scarce for the studied region. The objective of this study was to determine the maximum crop evapotranspiration (ETc), the single crop coefficient (Kc) and dual (Ke and Kcb) and the irrigation water use efficiency of the green dwarf coconut in a commercial plantation under the microclimatic conditions of Santa Izabel do Pará, Brazilian Amazon. The experiment was approximately in an irrigated area of 7 ha (01º 13’ 40,16” S e 48º 02’ 54,35” W), with coconut-pot plants in the fourth year of production. A micrometeorological tower was installed in the area to perform measurements of incident global radiation, radiation balance, soil heat flux, air temperature and relative air humidity, wind speed, rainfall. The maximum evapotranspiration was determined by the energy balance method – Bowen ratio, the simple (Kc) and dual (Kcb and Ke) coefficients, the evapotranspiration of refrence by the Penman-Monteith-FAO56 method and the efficiency of water use in terms of fruit production as well as of coconut water production. The accumulated evapotranspiration of the coconut tree in the period from August to November was 488.88 mm (2020) and 480.09 mm (2021), which correspond to the months of irrigation management. ET0 underestimated the water needs of the coconut tree, being 5.1% lower than ETc. The mean values of Kc, Kcb and Ke were 1.1, 0.51 and 0.56, respectively. The volume of coconut water per fruit and the weight of the fruits increases during the wettest period and decrease in the less rainy season, even with the use of the irrigation system. The WUEf was 1.87 fruits m-3 (2020) and 2.94 fruits m-3 (2021) and the WUEac 0.66 L m-3 (2020) and 0.98 L m-3 (2021). These results demonstrate that environmental conditions influence the water demand of coconut palm swells and are fundamental for a more efficient management of irrigation systems, contributing to the sustainability of water resources.