Tomatoes - Fertility

Nitrogen

Fresh-Market Tomatoes

Avoid late side-dress applications. They may prune the roots and cause blossom-end rot. If additional nitrogen is required late in the season, it may be injected through the irrigation system.

Processing Tomatoes

The nitrogen rate will vary greatly, according to the variety, soil type, crop rotation, organic matter and soil management. Apply nitrogen as a preplant broadcast application according to the recommendations in Table 9-92, Processing Tomatoes Nitrogen Recommendations.

Broadcast and incorporate the recommended preplant nitrogen with all the required phosphate. Inject equal amounts of soluble nitrogen and potash through the drip tape according to the schedule in Table 9-93, Fertigated Tomatoes Nitrogen Recommendations. Do not inject fertilizers containing phosphorus through the drip line.

Table 9-92. Processing Tomatoes Nitrogen Recommendations

Table 9-93. Fertigated Tomatoes Nitrogen Recommendations

Fertigated Tomatoes

Broadcast and incorporate the recommended preplant nitrogen with all the required phosphate. Inject equal amounts of soluble nitrogen and potash through the drip tape according to the schedule in Table 9-93, Fertigated Tomatoes Nitrogen Recommendations, above. Do not inject fertilizers containing phosphorus through the drip line.

Phosphorus

Test the soil to determine phosphorus requirements. Where the soil test values are 61 mg P per L soil (ppm) or higher, tomatoes are unlikely to respond to additional phosphate applications. For soils testing lower than 61 mg P per L soil (ppm), see Table 1-10, Phosphorus Requirements: Vegetables on Mineral Soils, on page 12.

Potassium

Test the soil to determine potassium requirements. Where the soil test values are 181 mg K per L soil (ppm) or higher, fresh-market and paste tomatoes are unlikely to respond to additional potash applications. For whole-pack tomatoes, use a higher threshold of 250 mg K per L soil (ppm).
For soils testing lower than the threshold values listed above, see Table 1-12, Potassium Requirements: Vegetables on Mineral Soils, on page 14.

Starter Solution (all tomatoes)

Apply a high-phosphorus starter fertilizer in the transplant water when transplanting tomatoes. Starter fertilizer is especially important when planting in cool soils. Starter fertilizers are available in several forms, including liquids (10-34-0 or 6-24-6) or granular materials (10-30-20 or 10-52-10). Apply according to the recommendations in Table 9-94, Tomato Starter Solution Recommendations.

Table 9- 94. Tomato Starter Solution Recommendations

Magnesium

A magnesium deficiency may occur on tomatoes. The usual symptoms are yellowing of older leaves while the veins remain dark green. Excessive potash applications may induce a magnesium deficiency. Reduce potassium fertilizer rates on soils testing less than 100 ppm. Adjust the potassium rate proportionally to a minimum of 50% at 50 ppm Mg. See the section Micronutrients, on page 16, and Table 1-13, Application Rates for Magnesium, Calcium and Micronutrients, on page 16.

Plant Analysis

When used in conjunction with a soil analysis, plant analysis is a useful tool for diagnosing crop problems or for evaluating a fertilizer program. The objective of a good fertilizer program is to maintain tissue nutrient concentrations on the lower side of the sufficiency range. Attempting to bring the nutrient analysis up to the higher end of the range could possibly result in over-fertilization and may not be economical. For more information see the section, Plant Analysis, on page 3.

Only use sufficiency ranges as a reference and a guideline. Plant analysis does not replace soil testing or a sound soil fertility program. See Table 9-95, Tomato Nutrient Sufficiency Ranges.

Table 9-95. Tomato Nutrient Sufficiency Ranges

Plant Part: Most recently matured leaf

Adapted from Maynard, D.N., and G.J. Hochmuth. 1997. Knott's Handbook for Vegetable Growers, 4^th Edition. John Wiley & Sons, Inc. New York.

Related Links

• Publication 363 - Vegetable Production Recommendations

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