| Fertilizer | Cups per 100 Square Feet(a) |
Pounds per 100 Square Feet(b) |
Teaspoons per foot of shrub height |
| 8-8-8 | 2.5 | 1.25 | 4 |
| 10-10-10 | 2.0 | 1.00 | 3 |
| 13-13-13 | 1.5 | 0.77 | 2 |
| 15-15-15 | 1.3 | 0.67 | 2 |
| 15-0-15 | 1.3 | 0.67 | 2 |
| Ammonium nitrate (33-0-0) | 0.6 | 0.30 | 1 |
| Sodium nitrate (16-0-0) | 1.3 | 0.63 | 2 |
| Ammonium sulfate (21-0-0) | 1.0 | 0.48 | 1 1/2 |
| Urea (46-0-0) | 0.4 | 0.22 | 1/2 |
| Muriate of potash (0-0-62) | 0.3 | 0.16 | 1/2 |
| Sulfate of potash (0-0-50) | 0.4 | 0.20 | 1/2 |
| Superphosphate (0-20-0) | 1.0 | 0.50 | 1 1/2 |
| Bonemeal (0-20-0) | 1.0 | 0.50 | 1 1/2 |
| Triple superphosphate (0-46-0) | 0.4 | 0.22 | 1/2 |
| Ground limestone(b) | 10.0 | 5.00 | 15 |
(a)The numbers in these columns are also equal to the cups or pounds of fertilizer per inch of tree trunk diameter at a 4-foot height. (b)These rates of limestone are equivalent to applying one ton per acre.
To stimulate growth, fertilize three times a year. Normally, the first fertilization is made in February for trees and in March or April for shrubs. Space later fertilizations 2 months apart. If the trees or shrubs are large enough, fertilize only once or not at all. Do not fertilize later than mid-August with N, or the new growth is likely to be injured by cold weather.
For roses and annuals, follow soil test recommendations for lime, P, and K, then fertilize with N monthly from March through August at half the rates recommended for shrubs. Perennial herbaceous ornamentals, such as tulips, irises, daffodils, dahlias, peonies, and daylilies, can be fertilized at the same rates as shrubs. However, one N application per year is usually sufficient. Disease and insect infestations are more likely when lush growth is stimulated by high rates of N.
1. An established bed of daylilies, about 10 feet wide and 15 feet long.
Soil test recommendations: no lime, 120 pounds N per acre, 40 pounds P2O5 per acre, and 120 pounds K2O per acre. The comment on the soil test report suggests: per 100 square feet, in March apply 2.5 cups 8-8-8; in May and July apply 1.3 cups 15-0-15.
The bed is 150 square feet (10 x 15 = 150). Therefore, half again as much fertilizer as suggested per 100 square feet will be needed (150 ÷ 100 = 1.5) in each application:
2.5 cups 8-8-8 x 1.5 = 3.75 cups 8-8-8
1.3 cups 15-0-15 x 1.5 = 1.95 cups 15-0-15
However, 8-8-8 and 15-0-15 are not available in the local garden store! A 13-13-13 fertilizer, ammonium nitrate (33-0-0), and muriate of potash (0-0-62) are available. The 13-13-13 can be substituted for the 8-8-8 if the right amount is used. Referring to the table, you see that:
2.5 cups 8-8-8 = 1.5 cups 13-13-13
1.5 cups 13-13-13 x 1.5 (for 150 sq ft) = 2.25 cups 13-13-13
Ammonium nitrate and muriate of potash can be substituted for the 15-0-15 (again, from the table):
1.3 cups 15-0-15 = 0.6 cups ammonium nitrate + 0.3 cups muriate of potash
0.6 cups ammonium nitrate x 1.5 (for 150 sq ft) = 0.9 cups ammonium nitrate
0.3 cups muriate of potash x 1.5 (for 150 sq ft) = 0.45 cups muriate of potash
Therefore, this daylily bed can be fertilized in March with 2.25 cups 13-13-13, and in May and July with 0.9 cups ammonium nitrate plus 0.45 cups muriate of potash.
2. Chinese hollies around a home, all about 4-feet tall.
Soil test recommendations: 1 ton lime per acre, 120 pounds N per acre, 80 pounds P2O5 per acre, and 40 pounds K2O per acre. The report suggests: per 100 square feet, apply 5 pounds lime now; in March apply 2.5 cups 8-8-8; in May apply 1.0 cup superphosphate; and in May and July apply 0.6 cups ammonium nitrate.
Now use the table to convert fertilizer materials to a per foot of shrub basis:
First, apply lime as recommended to the soil:
Lime = 5 pounds per 100 square feet
8-8-8 = 4 teaspoons per foot of shrub
Superphosphate = 11/2 teaspoons per foot of shrub
Ammonium nitrate = 1 teaspoon per foot of shrub
Now multiply these figures by four, since the shrubs are 4-feet tall. This will give you the actual amount of fertilizer material you will need to apply.
3. A rose bed.
Soil test recommendations: no lime, 120 pounds N per acre, 40 lbs P2O5 per acre, and 80 pounds K20 per acre. The report suggests: per 100 square feet, in March and May apply 1.25 cups 8-8-8; in April and June apply 0.65 cups 15-0-15; and in July and mid-August apply 0.3 cups ammonium nitrate.
You already own a lawn fertilizer with a 24-8-16 analysis. No pesticides are in this product, so it is safe to use if used at the proper rate. Also this fertilizer contains the same ratio of nitrogen, phosphorous, and potassium as recommended by the soil test results. Therefore, it can be used for each of the six fertilizations alone to provide the needed nutrients. Roses should be fertilized monthly at half the rate of normal shrubs. This rate should be 0.05 pound nitrogen per 100 square feet. To determine the amount needed, divide the pounds of N desired by the percentage of N in the fertilizer:
0.05 pound N desired ÷ 0.24 pound N per pound of 24-8-16 = 0.21 lb of 24-8-16
So, 0.21 pound of 24-8-16 per 100 square feet per application will supply the recommended nutrients at the correct rate. This would be about 0.4 cup of 24-8-16 per 100 square feet or 1/2 teaspoon per foot of height of each rose.