Uptake Efficiency and Requirement Using 15 N in Tomatoes Grown on Sandy Soils.

In the absence of a reliable soil test, nitrogen (N) is applied based on research data showing the general requirement of different crops grown in different soils and under different management conditions around the world. However, the uptake efficiency of applied N is estimated to be only around 50% for most crops. In sandy soils particularly, leaching may be a potential pathway for loss. Therefore, it is important to improve our understanding of crop N requirement and uptake efficiency. A replicated field study to determine both crop N requirement and N uptake efficiency in tomatoes (var. BHN 602) grown in sandy soils under a plastic-mulched bed system was conducted in north Florida using ¹⁵N-ammonium nitrate. Spring tomatoes were followed by a Fall tomato crop in the same field for determining the residual soil N. Data from the spring season tomato experiment are presented here showing the crop N requirement and the N uptake efficiency.