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  • Author or Editor: Jack E. Rechcigl x
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A renewed interest in sulfur (S) deficiency has occurred because of reductions in atmospheric depositions of S caused by implementation of clean air regulations around the world. In vegetable production systems, other sources of S exist, such as soil S, fertilizers, and irrigation water. While soil testing and fertilizer labels impart information on quantity of S, it is unknown how much S within the irrigation water contributes to the total crop requirement. Two studies were conducted to determine the influence of elemental S fertilization rates and irrigation programs on tomato (Solanum lycopersicum) growth and yield. Irrigation volumes were 3528, 5292, and 7056 gal/acre per day and preplant S rates were 0, 25, 50, 100, 150, and 200 lb/acre. Data showed that neither plant height, leaf greenness, soil pH nor total soil S content was consistently affected by preplant S rates. During both seasons, early marketable fruit weight increased sharply when plots were treated with at least 25 lb/acre of preplant S in comparison with the nontreated control. Early fruit weight of extralarge and all marketable grades increased by 1.5 and 1.7 tons/acre, respectively, with the application of 25 lb/acre of S. There were no early fruit weight differences, regardless of marketable fruit grade, among preplant S rates from 25 to 200 lb/acre. Based upon this result, adding preplant S to the fertilization programs in sandy soils improves tomato yield and fall within the current recommended application range of S (30 lb/acre) for vegetables in Florida. At the same time, irrigation volumes did not consistently influence soil S concentration, soil pH, leaf S concentrations or tomato yield, which suggested that irrigation water with levels of S similar to this location [58 mg·L−1 of sulfate (SO4) or 19 mg·L−1 of S] may not meet tomato S requirement during a short cropping seasons of 12 weeks, possibly because microbes need longer periods of time to oxidize the current S species in the water to the absorbed SO4 form.

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