Winter irrigation increased yield of ‘Washington’ navel orange (Citrus sinensisL. Osbeck)

Abstract

SummaryThe present study aimed to quantify the effect of withholding irrigation during the winter season in southern California on the productivity of ‘Washington’ navel orange and to determine whether the additional expense of irrigating navel orange trees during the winter is a cost-effective production management strategy. Yield and fruit size were quantified for 30 year old ‘Washington’ navel orange scions on Troyer citrange rootstock which were rain-fed from October 1 to March 1 in each of three successive years and for another set of trees which were irrigated during the winter. Supplementing winter rainfall with irrigation significantly increased the weight of fruit per tree in all three years of the study (45 ± 17 kg fruit tree−1, n = 3 years) and number of fruit per tree in the two years in which the rain-fed, –winter irrigation trees had significantly lower predawn water potentials than the +winter irrigation trees. Despite the yield increases which resulted from supplementing winter rain with i...