Evapotranspiração e viabilidade econômica da irrigação no cacaueiro na região transamazônica.

Abstract

The cocoa tree (Theobroma cacao L.) has high socioeconomic importance for the Transamazon region, with increasing demand for its beans for chocolate production and other industrial segments. However, information supporting decision-making and efficient irrigation management for this crop in the region remains limited. Therefore, this study aimed to quantify crop evapotranspiration (ETc), determine the crop coefficient (Kc), and evaluate the economic feasibility of irrigation in cocoa cultivation in the northwestern region of the state of Pará, Brazil. The experiment was conducted in a 10 ha commercial plantation of seed propagated cocoa in the municipality of Vitória do Xingu, Pará. A micrometeorological tower was installed in the area to measure air temperature and relative humidity, global solar radiation, rainfall, soil moisture, and wind speed. Reference evapotranspiration (ET0) was calculated using the FAO-56 Penman–Monteith method, while crop evapotranspiration was estimated through the soil water balance method. Crop coefficients (Kc) were determined, and an economic feasibility analysis of irrigation was performed. Mean ET0 was higher during the less rainy period, with an increase of 25.14%. In the irrigated system, crop evapotranspiration (ETc) averaged 3.03 ± 0.79 mm day-1 during the rainy season, increasing to 4.02 ± 0.84 mm day-1 in the dry season. Under rainfed conditions, mean ETc was 2.98 ± 0.67 mm day-1 in the rainy period, decreasing to 1.53 ± 0.23 mm day-1 in the less rainy period. Crop coefficients (Kc) in the irrigated treatment were 0.84 in the rainy period and 0.89 in the less rainy period, whereas in the rainfed treatment they were 0.83 and 0.34, respectively. The economic analysis demonstrated that irrigated cultivation showed superior performance compared to rainfed cultivation, with higher net present value (NPV), internal rate of return (IRR), benefit–cost ratio (B/C), and shorter payback period. Thus, irrigation represents a viable alternative for producers. The present study indicates that edaphoclimatic conditions determine the water demand of cocoa, playing an essential role in irrigation efficiency and water sustainability.