When properly fertilized, tomatoes can thrive.

How Often Should You Fertilize Tomato Plants?

by Kimberly Caines

If you're a mom with a green thumb, growing tomatoes (Lycopersicon esculentum) can be an ideal, money-saving venture. This member of the Solanaceae family is a good source of fiber, potassium and vitamins A and C, and can be eaten in many ways including raw, stewed, grilled and sauteed. Tomato plants are challenged with producing branches, foliage, blossoms and fruit. To successfully do this, they count on you to provide several applications of fertilizer, starting even before you transplant them.

1. Soil Test

Tomatoes thrive in soil with a pH range between 6.0 and 6.8. The pH is an indication of available nutrients in the soil. Before starting tomatoes, use a commercial soil test or consult your local Cooperative Extension Service about soil testing. If the test results indicate that your garden's soil has a low pH, you can incorporate limestone into the top 7 inches of soil to raise it. If the pH is high, tilling sulfur into the soil can lower it.

2. Before Transplanting

Fertilizing the soil before transplanting gives tomatoes a good start. Apply a 5-10-10 or 5-10-5 fertilizer at a rate of 2 pounds per 100 square feet. Incorporate the fertilizer in the soil to a depth of 6 inches. Another way to apply the fertilizer is to dig a long, 6- to 8-inch-deep furrow in the row where you plan to grow the tomatoes. Sprinkle a thin band of fertilizer in the furrow, and cover it with 3 inches of soil. Then, transplant the tomato plants on top of this to prevent direct contact between the fertilizer and tomato roots.

3. Side Dressing

Because the initial fertilizer application isn't enough to last throughout the growing season, side-dressing with fertilizer is required. When the fruit is about the size of a golf ball, dig a 1-inch deep, circular furrow in the soil around each tomato plant. Make the circle in a 6-inch diameter around the stem. Sprinkle 1 1/2 tablespoons of a 5-10-10 fertilizer in each furrow and cover it with 2 inches of soil. Then, water it in. Side-dress the plants again in the same way about two weeks after you pick the first fruit, and again, one month hereafter.

4. Considerations

Observing your tomato plants can indicate whether you're correctly fertilizing them. Nutrient deficiencies can trigger symptoms, such as blossom-end rot, in which the bottoms of the fruit turns brown. The flower buds can turn yellow and drop off the plant, growth might be stunted and the leaves can discolor and turn yellow, brown, or dark or light green. Also, avoid fertilizing with too much nitrogen, because this can cause the plant to focus more on developing foliage than fruit.

Photo Credits

  • Ryan McVay/Photodisc/Getty Images