Gains in citrus fruit quality through regulated irrigation

Results of several South African irrigation experiments are compared to find a clear picture of the relationship between citrus fruit quality and irrigation timing as well as quantity of water. These trials include Valencia, grapefruit and navel orchards. Generally fruit size was the most sensitive quality indicator of poor irrigation practices. Phase II (cell enlargement) was the most sensitive to water stress in Valencias, but phase I (flowering and cell division) was more important in grapefruit and navels. Fruit size recovery after alleviation of water stress was better in Valencias than in either grapefruit or navels. In the main experiment, Olinda Valencia on Cairn rough lemon was subjected to two levels of water stress during each of three phenological stages. Total soluble solids (TSS) and acidity in the juice decreased with increased volume of water applied. Both TSS/acid ratio and juice content were positively correlated with quantity of irrigation water, particulatly during phase II. Rind thickness increased as a result of water stress in all experiments. Water management guidelines for the production of highest fruit quality are proposed, taking into account water use efficiency.