Net radiation partitioning, evapotranspiration, and crop coefficients of the green dwarf coconut in Santa Izabel do Pará, Brazilian Amazon

Abstract

Inadequate management of the irrigation system has compromised yield and favoured the degradation and waste of water resources. To ensure efficient irrigation management, providing yield increases, sustainability in the use of water resources and reduction of production costs, studies about the water demand of coconut palms are needed. The objective of this study was to determine the energy partition, crop evapotranspiration (ET c ), and the simple crop coefficients (K c ) of the green dwarf coconut palms in Santa Izabel do Pará, Pará, Brazil. The experiment was carried out in a coconut plantation at Reunidas Sococo Farm, with an area of approximately 7 ha in a triangular spacing of 7.5 × 7.5 m, during 2020 and 2021. The ETc was determined by the Bowen ratio method, with measurements of temperature and relative humidity at two levels above the crop canopy and reference evapotranspiration (ET o ) by the FAO Penman-Monteith method, using data from the National Institute of Meteorology. The K c was determined by the ratio between ETc and ETo. The total water demand of the coconut palm was 489 (2020) and 480 mm (2021), with a daily average of 4.21 (2020) and 4.14 mm (2021) for the dry season. The mean value of K c was 1.06 (± 0.12). Evapotranspiration was driven mainly by energy availability, associated with a control of atmospheric demand on K c values, suggesting a possible influence of coconut trees on Kc values even under good water availability and small variability in vegetation cover.