Effect of Sulfur-coated Urea on Yield, N Uptake, and Nitrate Content in Turnip Greens, Cabbage, and Tomato1

In a 3-year study sulfur-coated urea (SCU) resulted in differences in crop response which were related to the different N release rates. On Decatur silty clay loam at Normal, Alabama, SCU with relatively high N-dissolution rates performed best in terms of yield and N uptake for turnip greens, Brassica campestris L. (Rapifera group) while SCU with a slower dissolution rate performed better on Morrison sandy loam at Tuskegee, Alabama. On cabbage, Brassica oleracea L. (Capitata group) SCUs performed similar to ammonium nitrate (AN) and uncoated urea (UCU). With tomato, Lycopersicon esculetum Mill., spring-applied SCU with the highest dissolution rate, performed as well as split applications of AN, indicating the possibility for labor saving with SCU through reduced number of applications. Effect of SCU on nitrate accumulation was minimal. At harvest in the top 15 cm soil the total N content was highest in tomato plots treated with split AN, followed by SCU-A, SCU-C, and AN, respectively.