Supplement to the Soil Test Lab Report and Recommendations from the Jefferson County, Florida, Extension Service
Most garden vegetables yield best in soil with a pH between 5.5 and 6.5. Calcium, an ingredient in limestone and gypsum, may prevent blossom end rot of vegetables such as tomatoes and watermelons. If you have not limed the garden in the past 3 to 4 years, a pH test should be run.
Always have your garden soil pH checked before applying lime. The County Extension staff will help you prepare a sample for analysis. The cost of a pH test and lime recommendation from the University of Florida extension soil testing lab is $3.00. A complete analysis costs $7.00, and provides tests for phosphorous, potassium, calcium, magnesium and lime. The results are sent to you, with copies to the Extension Office. Come by the office for a copy of the Landscape and Vegetable Garden Soil Test Information Sheet (SL-136) or print out a .pdf version.
Fertilizers which are commonly available to gardeners in Jefferson County are 8-8-8, 10-10-10, 5-10-15, 16-4-8, 20-5-10, 15-0-14, 20-0-20 and ammonium nitrate (34-0-0). The numbers are percentages of nutrient or pounds per hundred pounds of fertilizer. They are always in the order of nitrogen-phosphate-potash (N – P205 – K20). Different analysis fertilizers may be used to provide garden plants with the nutrient levels recommended on the soil test report. Fertilizers of similar ratios may be substituted according to availability and price. To achieve the same level of fertilization as one pound of 10-10-10, you may use 1-2/3 pounds of 6-6-6, or 1-1/4 pounds of 8-8-8, or 3/4 pound of 13-13-13.
Garden fertilizer rates on the other side of this page are for application when you have not had a soil sample tested. The test may indicate significant levels of nutrients in the soil, allowing reduced fertilizer application. In many cases, garden soils test high for phosphorus (P), and little or no phosphate (P205) fertilizer need be applied. When test results show high or very high levels of P, substitute 2/3 pound of 15-0-14 or 1/2 pound of 20-0-20 for each pound of 10-10-10. Likewise, if soil test results show high or very high potassium (K) levels, use a fertilizer with relatively low potash (K20) content.
High concentrations of fertilizer may reduce seed germination or cause seedling damage due to salt injury. Place planting-time fertilizer below and to the side of seed. Heavy rainfall or irrigation can “leach” fertilizer beyond the plant’s root zone or cause it to run off. The fertilizer may eventually pollute surface and ground water. Nitrogen and potassium are relatively soluble and subject to leaching. Applying fertilizer at lower rates and more often is more desirable than fewer large applications.
Often a water soluble “starter fertilizer” is used to water in transplants. Some garden centers carry 8-32-16, 12-24-12, 15-30-15, 20-20-20 or similar water soluble fertilizers which are mixed at the rate of 2 tablespoons per gallon of water. Apply 1 cup of this solution around the base of transplants as they are set in the garden.
- 1 cup of fertilize weighs about ½ pound
- 1 pint of fertilizer weighs slightly less than 1 pound
- 1 quart of fertilizer weighs about 1¾ pounds
- There are 43,560 square feet per acre
| Crops | Amount and analysis of fertilizer per 100 sq.ft. area* | Additional fertilizer rates, analyses, and timing for sidedress applications per 25 ft of row length |
|---|---|---|
| Corn | 1½-2 lbs of 10-10-10 or 5-10-15 | 1 pound of Ammonium Nitrate or 1½ pounds of 20-0-20 when plants are 8-10″ high and again when tassels show on ½ of stalks |
| Squash and Cucumbers | 1-1½ lbs of 10-10-10 | ½ pound of 10-10-10 or ¼ pound of 20-0-20 every 10 days to two weeks or as leaves turn to light green |
| Beans | 1-1½ lbs of 10-10-10 | ½ pound of Ammonium Nitrate or 1 pound of 20-0-20 when first blooms show |
| Southern Peas | ½-1 lb of 10-10-10 | ¼ pound of Ammonium Nitrate or ½ pound of 20-0-20 when first blooms show |
| Greens | 1½-2 lbs of 10-10-10 | ½ pound of 20-0-20 three weeks after plants emerge and again three weeks later |
| Tomatoes | 3 lbs of 10-10-10 | 2 pounds of 10-10-10 when fruit are 1½” in diameter, and 1 pound of Ammonium Nitrate (or 2 pounds of 20-0-20) two weeks after picking the first ripe tomatoes. Repeat one month later |
| Pepper and Eggplant | 1½-2 lbs of 10-10-10 | 1-1½ pounds of 10-10-10 or ½ pounds of 20-0-20 every 3 to 4 weeks |
| Potatoes | 1½-2 lbs of 10-10-10 | 1 pound 10-10-10 after 3 weeks and 1 pound Ammonium Nitrate or 1½ pounds of 20-0-20 after tuber formation begins |
| Sweet Potatoes | 2 lbs of 5-10-15 | 1 pound of 20-0-20 after 3 to 4 weeks |
| Okra | 1½-2 lbs 5-10-15 | ¼ pound 20-0-20 after first pods are cut and every 3 to 4 weeks later |
| Onions | 1½-2 lbs 10-10-10 | 1 pound of 10-10-10 every 3 to 4 weeks |
| Strawberries | 1½ lbs of 10-10-10 broadcast and 1½ lbs 10-10-10 banded 4-6″ between rows in the bed and 6″ below the crowns | Mulched beds should not need additional fertilizer |
| * Applied broadcast and thoroughly mixed into the soil prior to planting; half of this rate may be broadcast or spread and the remainder applied as a band 2-3 inches beside and 2-3 inches below the seed drill. Never allow seed to come into direct contact with or to be planted directly above the fertilizer band. | ||
To select the equivalent nutrient rates from organic sources, see Organic Vegetable Gardening (including fertilizer sources and rates). Also refer to Jim Stephens’ Fertilizing the Vegetable Garden.