The Effects of Rainfall and Irrigation Management on Citrus Juice Quality in Texas1

Juice yield, degrees Brix (soluble solids), citric acid, suspended solids, L-ascorbic acid (Vitamin C), pH, and naringin content in grapefruit were measured from 1969–1975 on 2 sizes of ‘Marrs’ and ‘Valencia’ oranges, Citrus sinensis (L.) Osbeck, and ‘Ruby Red’ grapefruit, C. paradisi Macf., subjected to 4 irrigation management regimes in an area where rainfall contributes about half the annual water requirement. Irrigation main effects in individual years were influenced by variable annual amounts and seasonal distribution of rainfall. Vitamin C, juice yield, pH, and suspended solids were only occasionally affected by irrigation treatment. Citric acid content of ‘Valencia’ orange juice was consistently higher and the citric acid and Brix of grapefruit juice were usually higher in the 2 less frequently irrigated treatments, regardless of rainfall. Among-years analyses of variance showed significant reductions in Brix, citric acid, and suspended solids with increased frequency of irrigation for all cultivars.