The best approach to fertilizing a garden is to follow the soil test recommendation. Spread lime and other fertilizer (evenly and uniformly) over the entire garden area. Gardeners who prefer to add fertilizer to the row should place it at least 3 inches below and 2 to 3 inches to the side of the seed position. Closer placement may result in fertilizer burn and poor stands.
If the soil was tested last year but not tested for the current season, apply the fertilizer at the same rate as the previous year. Do not apply lime until another test is taken. Poor growth and nutrient deficiencies may occur with too much lime.
Applying limestone when needed according to soil test results will benefit the garden in two ways. It eliminates some acid in the soil and allows plant nutrients to become more available to plants. Limestone is also a form of fertilizer because it contains calcium, a necessary nutrient for plant growth. Dolomitic limestone also contains magnesium, which is essential for plant growth. Lime effectiveness is increased by grinding, and the smaller the particles, the faster it will become effective in reducing acid. Pulverized limestone is the most effective form of agricultural limestone. Other types of lime are sold but must be used at differing rates. All recommendations are based on the use of agricultural limestone.
If a recent soil test is not available, apply 5-10-10 at the rate suggested in Table 1. This initial preplant application will normally supply all of the phosphorous and potash needed by most garden vegetables. Nitrogen requirements vary from crop to crop, and heavy rainfall may cause nitrogen to leach from the soil. For these reasons additional nitrogen may be required.
The application of fertilizer after plants are established is called sidedressing, and some plants respond more than others. This application should contain primarily nitrogen. Apply in a band along one side of the row and about 4 to 6 inches from the plants, depending on the plant size. Repeat this application if your garden is sandy. An additional application of general fertilizer (the same as you applied preplant) will be beneficial after heavy (3 inches or more) rains.
Calcium nitrate is often suggested as a sidedressing material. There are many others that could be used. Table 2 lists some sidedressing fertilizers and the suggested rate for each. Other materials can be used by comparing their nitrogen content. Some crops do not require a lot of extra nitrogen. Table 3 gives a general idea of required sidedressing applications based on the kind of crop grown.
Table 1. Suggested Fertilizer Application Where No Soil Test has Been Taken
|Time of Application||Rate of Application|
|Apply preplant||5-10-10 fertilizer at 30 pounds per 1,000 sq feet|
|Apply 4 weeks later (sidedressing)||Calcium nitrate at 7 pounds per 1,000 sq feet or 2 pounds per 100 feet of row|
Table 2. Commonly Available Sidedressing Fertilizers & Rates of Application
|% N||pounds/100 feet of row|
|Ammonium sulfate & urea||34.0||1|
Table 3. Sidedressing Schedule for Selected Vegetables Crop
|Crop||Type Fertilizer¹||Number of Times per Season|
|Tomato||Nitrogen or complete fertilizer||1|
|¹Apply 0.3 pounds of actual nitrogen per 100 feet of row.
²Sources of nitrogen may include synthetic materials such as 5-10-10 and urea or natural materials such as bloodmeal or cottonseed meal.
Excerpted from the South Carolina Master Gardener Training Manual, EC 678.