The 2009 ASHS Annual Conference

There has been a renewed interest in sulfur (S) deficiencies because of the reduction in atmospheric depositions. Sulfur deficiencies are often confused with other deficient elements such as nitrogen (N). Tomato production in Florida is typically on deep Spodosols (fine sand) with low organic matter (>2%) and therefore inherently low in organic and inorganic S. Previous studies have found a positive response to the addition of S to fertilizer programs, regardless of source or form. Two studies were conducted in 2008 to determine the influence of S fertilization rates and irrigation programs on tomato growth and yield. The irrigation programs were 3528, 5292, and 7056 gallons of water per acre per day. The S rates were 0, 25, 50, 100, 150, and 200 lbs S per acre.  Irrigation program increased vigor early in the season before fruit set, but did not continue to influence visual vigor ratings as the fruit were set. Chlorophyll content was not influenced by irrigation program or S fertilization rates. In the first study, the first harvest of tomatoes, the rate of 25 lbs/A S increased yield by 26% over the non-treated control.  Increasing the S rate beyond 25lbs/A S had less yield than 25 lbs/A S, but more than the non-treated control.