An Evaluation of Sulfur-coated Urea as a Preplant Total Season Nitrogen Supply for Trellised Tomatoes
1976
Shelton, J. E.
The use of a controlled release N source for the production of trellised tomatoes (Lycopersicon esculentum) which require frequent topdressings would be desirable. Three sulfur-coated urea (SCU) materials having release rates of 11.4, 21.5, and 29.3% over a 7-day period were compared to NH₄NO₃ applied preplant or as multiple applications. Nitrogen rates were 392, 560, and 729 kg N/ha. Marketable yields from an application of SCU₁₁.₄ at 392 or 560 kg N/ha were greater than with the same rate of N as NH₄NO₃ either as preplant or split applications. When SCU₂₁.₅ or SCU₂₉.₃ was used, the yields were comparable to a single application of NH₄NO₃. Differences in fruit number per plot were not significantly related to treatments. However, there was a significant difference in average fruit weight which was correlated with total yield. Tissue N content was highest at the first sampling from a single application of NH₄NO₃ and lowest from SCU₁₁.₄. However, at later sampling periods the N content was maintained at a higher level with SCU₁₁.₄. Although 729 kg N/ha as a single application of NH₄NO₃ detrimentally affected plant growth and production, this effect was not noted with the sulfur-coated urea materials.
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