Abstract
Two field studies were conducted to determine the effect of S fertilization on tomato (Lycopersicon esculentum Mill.) yield and foliar S concentration. The soil had very low S content (<30 ppm) and 1.5% organic matter. Fertilizer sources were: 1) ammonium nitrate (AN; 34% N) at a rate of 300 lb/acre of N; 2) AN + potassium sulfate (PS; 23% S and 55% K) at rates of 300 + 343 lb/acre of N and S; 3) ammonium sulfate nitrate (ASN; 26% N and 14% S) at a rate of 300 + 343 lb/acre of N and S; and 4) a non-treated control. Muriate of potash (60% K) was used to balance total K amounts in each treatment to ensure that this nutrient was under non-limiting conditions. Plots treated with either rate of AN or non-treated had the lowest foliar S concentration, ranging between 0.55% and 0.53%. However, plots treated with S-containing fertilizers increased foliar S concentration when compared with the non-treated control and AN-treated tomatoes. Average S concentration was about 0.74%, which was 40% higher than the concentration in non-treated control plots. There were no significant marketable yield differences in plots treated with either AN + PS or ASN. Average marketable yield ranged between 27.5 and 28.2 ton/acre in the S-treated plots. In contrast, average yield in the AN-treated plots was 18.7 ton/acre, which was 44% and 42% less than the yields in the AN + PS and ASN-treated plots. These results suggest that soil analysis should be performed in tomato fields before planting to determine appropriate S application rates.
