Nitrogen and Phosphorus Needs for Tomatoes and Green Peppers Grown with Drip Irrigation

Production of processing tomatoes and green peppers may be impacted by the regulation of nutrient management, because producers use high rates of nitrogen (N) and phosphorus (P) fertilizers. This experiment, initiated in 2002, aimed to determine the effects of N and P on yield and quality of the two crops, and on risk of nutrient losses under intensive management using drip fertigation.

In both of the first 2 years, P fertilizer increased the marketable yield of peppers, despite soil test levels so high that it would not have been recommended. However, in the last 2 years, the peppers did not respond to P.

Over 4 growing seasons (2002-2005), optimum marketable yields required 180 to 250 lb N/A for green peppers, and 190 to 270 lb N/A for tomatoes. These rates exceed the current recommendations by more than three-fold for peppers and two-fold for tomatoes. This information will provide an excellent basis for a change in recommendations. ON-27F