Preliminary results of the effects of annual fertilizer rates on tomato, cabbage, lima and snap bean yield and quality

Due to the comparatively low costs of fertilizer elements in recent years, vegetable growers have, in the past, frequently applied more fertilizer than soil tests have called for and have therefore raised the phosphorus and potassium levels to a point where additional applications may not significantly increase yields. In an attempt to determine what benefits can be obtained from further fertilization of these high testing soils, and to what degree fertilizer rates could be cut without significantly reducing yields, a five year study was undertaken at the University of Tennessee Plant and Soil Science Farm, the Plateau Experiment Station at Crossville, and the West Tennessee Experiment Station at Jackson. Tomatoes on one set of plots and cabbage followed by lima or snap beans on another were grown under seven different fertilizer regimes. Fertilization rates ranged from no fertilizer to 134 kg./ha. of nitrogen, phosphorus and potassium. . The experiment was to be run on the same plots for five consecutive years. The first year's results at all locations,and the second year's at the Knoxville location only, were available and included in this report.

Generally it was found that cabbage and tomatoes responded to nitrogen, a fertilizer element known to not carry over well at this southern latitude. Phosphorus and potassium response was not as pronounced in cabbage and was, in many cases, not evident. Lima and snap beans were, for the most part, adequately supplied by residual phosphorus and potassium levels in the soil. When they did show a response, it was between no fertilizer and the application of the first increment, with no apparent correlation between amount of fertilizer applied and yield of beans.

These preliminary results suggest that any decrease in fertilizer rates to counter increased fertilizer prices, which does not result in a decrease in yield, quality, or a delay in maturity will net the grower a wider margin of profit.