Water balance and crop coefficient estimation of a citrus orchard in Uruguay

摘要

The actual evapotranspiration (ETc) of mature 'Valencia' orange trees [Citrus S_1nenS_1s (L.) Osb.], drip-irrigated and non-irrigated, was calculated uS_1ng the water balance method, over three years. Annual ETc was 24% higher from irrigated trees that from non irrigated trees (767 and 620 mm year~(-1), respectively). Maximum monthly average ETc was 3.3 mm day~(-1) or 80 L tree~(-1) da~(-1)(trees were spaced at 6x4 m). Generally ETc rate was reduced in January, the month of maximum atmospheric demand, compared with December, even under fully irrigated trees. The average annual value of the crop coefficient (Kc) for irrigated trees was 0.69. Monthly Kc values also showed a clear seasonal trend, with minimum values in summer (0.60), intermediate values in autumn and spring (0.77 and 0.80, respectively) and maximum values in winter (0.87). These values provide a useful base for the deS_1gn and operation of micro-irrigation systems, for mature citrus trees in Uruguay.