RECLAIMED WASTE-WATER IRRIGATION AND FERTILIZATION OF MATURE REDBLUSH GRAPEFRUIT TREES ON SPODOSOLS IN FLORIDA

An experiment was designed to determine the effects of canal water and reclaimed wastewater on growth, yield, and fruit quality of mature (25-year-old) 'Redblush' grapefruit (Citrus paradisi Macf.) trees on sour orange (C. aurantium L.) rootstock. The study war conducted from 1 Oct. 1990 to 18 Apr. 1994 at a site adjacent to the Indian River County municipal wastewater treatment facility located near Vero Beach, Fla. Treatments included canal water applied based on one-third or two-thirds soil water depletion and reclaimed wastewater applied using microsprinklers at 23.1 mm/week (low), 30.7 mm/week (moderate) and 38.6 mm/week (high). Trees receiving low and moderate levels of reclaimed wastewater had the largest canopies and trunk diameters and highest yields, even though the amount of fertilizer applied was less than that of canal water plots, Leaf nutrient levels were generally within acceptable ranges for N, P, K, Ca, Mg, and Na except in 1991 when levels were deficient due to excessive rainfall and leaching, Leaf B levels were similar for all reclaimed wastewater treatments but were lower for the canal water treatment in 1992 and 1993. Fruit growth rate, fruit and juice weight, total soluble solids (TSS), titratable acidity (TA), and TSS : TA ratio were similar for all treatments in 2 of 3 years, Peel thickness was similar for all treatments, Heavy metal concentration in the reclaimed wastewater was at low or nondetectable levels, Similarly, enteric viruses in the effluent were always <0.003 plaque forming units/liter. Reclaimed wastewater irrigation significantly increased weed growth compared to the canal water treatment.