Irrigation management alters energy partitioning, crop coefficients, and productivity of ‘Tahiti’ acid lime

Abstract

ABSTRACT Climate variability poses a major challenge to tropical citrus production, especially in regions with marked water seasonality. This study aimed to evaluate the effects of irrigated and rainfed regimes on the crop coefficient, energy partitioning, and yield of ‘Tahiti’ acid lime grafted onto Swingle citrumelo. The study was conducted from 2023 to 2025 in Capitão Poço, Pará State, Brazil, using a completely randomized design with two treatments (irrigated and rainfed) and 10 replications, totaling 20 plots. Micrometeorological data were obtained from an automatic weather station installed in the experimental area, and crop evapotranspiration (ETc) was estimated using the soil water balance method. An irrigation depth of 4.42 mm (66.3 L) per plant per day was sufficient to increase the average fruit yield and to concentrate 50.8% of the 2024 agricultural production during the off-season. During dry periods, the irrigated regime showed an average ETc of 3.7 mm per day and a crop coefficient (Kc) of 1.0, both indicating conditions close to atmospheric evaporative demand. In contrast, the rainfed regime had an average ETc of 2.9 mm per day and a Kc of 0.8. Despite the yield increase, radiation balance analysis revealed sensible heat flux values approaching latent heat flux values, indicating differences in flux partitioning under drip irrigation. Total yield was higher in the irrigated system (40.67 t ha−1) compared to the rainfed system (19.50 t ha−1), with significantly greater yields during the off-season.