Evapotranspiration and Crop Coefficient of Economically Important Fruit Trees in the Eastern Amazon

This study aimed to determine the actual crop evapotranspiration (ETc act) and the crop coefficient (Kc) of economically important fruit crops in the Amazon, under both irrigated and non-irrigated conditions. The ETc act was determined using the soil water balance method, while Kc was determined using the ratio of ETc act to reference evapotranspiration (ETo). The treatments were evaluated during the rainy period (RP) and the less rainy period (LRP). During the RP, ETc act showed no significant differences between treatments, ranging from 2.26 to 3.03 mm day−1. During the LRP, the irrigated treatment (2.91 to 4.02 mm day−1) showed higher ETc act compared to the non-irrigated treatment (1.53 to 2.87 mm day−1). For the non-irrigated treatment, only the dwarf green coconut and the acid lime had a higher ETc act in the LRP than the RP, while the açaí palm and the cocoa showed lower values during the LRP. In general, ETc act remained below ETo, with Kc values ranging from 0.81 to 0.85 during the RP and increasing to 0.89–0.93 during the LRP. Irrigation provided water support to the studied fruit crops during periods of lower rainfall, meeting the higher atmospheric demand during the less rainy period.