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Fertilizing Guidelines

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University of Massachusetts Soil Testing Laboratory

Plants produce their own energy using air, water and sunlight, but require fertile soil or growth media to provide essential nutrients. Healthy, well-fed plants are better able to withstand environmental stress, diseases and insect pressure and compete with weeds. For a small investment, routine soil analysis can establish your soil's fertility level and determine if any corrective measures are required. Soil testing is the most effective tool available for determining lime and fertilizer needs to produce healthy plants and protect the environment. Soil testing removes the guesswork and prevents the risk of over or under liming and fertilizing. The University of Massachusetts Soil and Plant Tissue Testing Laboratory provides affordable analytical testing and research-based recommendations to support sustainable management decisions. See: UMass Soil and Plant Nutrient Testing Laboratory for more information soil testing.

The information below is a guideline for fertilizing plants in home gardens, lawns and landscapes.

How to Determine How Much Fertilizer to Use Based on Soil Test Recommendations

The numbers on a fertilizer bag refer to the percentage of nitrogen (N), phosphorus (P) and potassium (K) which are the nutrients needed in largest amounts by plants. Fertilizer is not a cure-all for plant problems and must be used as one of the tools for improving growth and health of the plant.

Fertilizer recommendations for home gardens may be given in pounds of N, P205 and K20 per 100 sq. feet. To determine how much fertilizer to use, divide the lbs. of the specific fertilizer material recommended in the soil test result by the percent of that same material in the fertilizer being used. When using percentages in calculations, convert the number to its decimal form.

For example: The soil test recommends .25 lb of nitrogen per 100 sq. ft. and you plan to use a 10-10-10 fertilizer, then this is how to figure how much fertilizer to use to supply 0.25 lb. of nitrogen.

0.25 (lbs of nitrogen from recommendations) divided by 0.10 (10% nitrogen in fertilizer) = 2.5 lbs of 10-10-10 fertilizer to supply 0.25 lb nitrogen per 100 sq. ft.

Natural Fertilizers: Rotted manures and compost are excellent soil conditioners and should be incorporated into the soil each year. However, to provide a balanced fertilizer, they must be used in combination with other materials. The following recipe could be used to provide a balanced fertilizer in place of a commercial type fertilizer and is equivalent to 40 to 50 pounds of 5-10-10. Apply each year per 1000 square feet of garden prior to planting:

1000 lbs. (25 bu.) compost or rotted, not dehydrated, manure source of N
20 lbs. bonemeal (10 qts.) source of P
30 lbs. wood ash (15 qts.) source of K

If large quantities of compost or manure are difficult to obtain, try using a combination of organic and synthetic fertilizers.

Vegetables and Flowers

Prior to planting: Broadcast 20 pounds of 5-10-5, 5-10-10 or 10 pounds 10-10-10 per 1000 square feet. Lime can be applied at the same time. Rake into the top few inches of soil.

Sidedress: During the growing season apply up to 20 pounds of 5-10-10 or 5-10-5 per 1000 square feet or band 8 ounces for every 10 feet of row or use half as much 10-10-10.

Flowering Bulbs

Prior to planting: Broadcast 2 pounds 5-10-10 or 1 pound 10-10-10 per 100 square feet.

Sidedress: As plants flower, apply 2 pounds 5-10-10 or 1 pound 10-10-10 and 2 pounds of bonemeal per 100 square feet.

Perennial Flowers

Early spring and again in early June: Broadcast 2 pounds 5-10-5 or 5-10-10 or 1 pound 10-10- 10 per 100 square feet.

Groundcovers

Early spring: Broadcast 2 pounds 5-10-5 pr 5-10-10 or 1 pound 10-10-10 per 100 square feet. When the foliage is dry, use a broom to shake off any fertilizer adhering to the leaves to prevent burning the foliage.

Small Fruits

Strawberries

Prior to planting: Two to five bushels aged manure or compost and 2 pounds 10-10-10 or equivalent per 100 square feet.

After planting: One to two pounds 10-10-10-10 per 100 square feet 4-6 weeks after planting and again in late August.

Fruiting Year: Do not apply fertilizer in the spring of the fruiting year as it results in large, soft berries.

After renovation: Four pounds 10-10-10 per 100 square feet over the rows when plants are dry.

Grapes

Prior to planting: Two to five bushels aged manure or compost per 100 square feet.

After planting: Commercial fertilizers are generally not necessary the year vines have been planted. If newly planted vines are growing poorly, 4-6 ounces 5-10-10 may be applied.

Bearing vines: Each year, double the rate listed above until plants reach maturity. Three to four pounds of 5-10-10 (or equivalent) per vine, per year is recommended for mature vines.

Raspberries

Prior to planting: One pound 5-10-5 or 5-10-10 or one-half pound 10-10-10 per 100 square feet.

Following years: Six to eight pounds 5-10-5 or 5-10-10 or three to four pounds 10-10-10 per 25 feet of row. Hand broadcast between rows as early as possible in spring.

Blueberries

Four weeks after planting: One-half to one ounce 10-10-10 or equivalent in a band around the base of the plant.

Following years: Increase rate of fertilizer by one to two ounces. (10-10-10) per year until mature. Mature blueberry bushes (7 years or older) require one-half pound of 10-10-10 per year applied in April. In addition (beginning 3 years after plants are set) apply ammonium sulfate at the following rates:

Years After Plants Are Set Oz. Ammonium Sulfate Per Plant
3 1.5
4 2
5 3
6 3.5
7+ 4

Tree Fruits

The amounts suggested below apply to young trees. Ten to fifteen pounds of 5-10-5 or 5-10-10 or five to eight pounds of 10-10-10 is sufficient for mature apple, plum, cherry and pear trees. Mature peach trees should not require more than fifteen to twenty pounds of 5-10-15 or 5-10-10 or seven to ten pounds of 10-10-10.

Pounds of Fertilizer/Year of Tree Age

Type of Tree 5-10-5 or 5-10-10 10-10-10
Apple, Plum, Cherry 1 1/2
Pear 1/2 1/4
Peach 2 1

Do not fertilize at time of planting. After growth starts the year of planting, scatter fertilizer within 1 foot of trunk. After the first year, fertilize trees annually sometime between mid April and early May. Fertilizer should be applied in a band extending from the tip of the branches to within three or four feet of the trunk of large trees.

Where mulches of hay or law clippings are used, the amount of fertilizer may be decreased after the mulch starts to decay. Where sawdust is used for mulch, the amount of fertilizer will probably need to be doubled because soil bacteria rob nitrogen from plants to break down the sawdust.

Trees are susceptible to boron deficiency which causes premature ripening of fruit and localized spots in the flesh of the fruit. Application of boron once every three years will prevent the occurrence of this deficiency in apple and pear trees. The rate of application per tree will vary with tree age and size. Apply one-quarter pound of borax (11.1 percent actual boron) or its equivalent under young trees. Be sure to note the percent of actual boron in the fertilizer being used to supply this element because applying an excessive amount of boron can cause tree injury. Boron fertilizers vary from approximately 11 to 21 percent actual boron. Apply the borax at the same time and the same way as other fertilizers used under fruit trees. Fruit trees mulched with lawn clippings and/or hay probably will not require any fertilizer except boron.

CAUTIONS: Do not apply more than the suggested amounts of borax since too much boron is toxic to trees. Do not fertilize fruit trees in the fall because it may cause winter injury.

Ornamental Trees and Shrubs

Newly Planted Ornamental Trees and Shrubs

Do not fertilize at time of planting. Instead, plant trees and shrubs in soil containing plenty of organic matter. After growing in this soil for two or three years, they may be included in a fertilizer program.

Types of Fertilizers

High nitrogen fertilizers such as 18-6-12 or 24-6-12 are best although garden fertilizers such as 10-10-10 will do as a substitute. Compost, well-rotted manures and cotton-seed meal are also good materials to use. The important point is to use a complete fertilizer containing nitrogen, phosphorus, and potassium. Because trees are not fertilized frequently, it is recommended that one-half to two-thirds of the nitrogen be in an organic or other slow release form.

When to Fertilize and How Often

Fertilize in early spring or late fall (October) after top growth has ceased. Generally it is safe to fertilize every 2 or 3 years.

Trees

Needle-type Evergreens: One pound 10-10-10 or equivalent per inch of trunk diameter (at 4 feet above ground). If the tree is over 6 inches in diameter, use 2 pounds per inch.

Non-Evergreen: Two pounds 10-10-10 or equivalent per inch of trunk diameter (at 4 feet over ground). If tree is over 6 inches in diameter, use 4 pounds per inch.

Flowering trees: One-half pound 10-10-10 per inch of trunk diameter (at 4 feet above ground).

Methods of Application

Surface Application: Recommended for trees with a 4-inch or less trunk diameter (at 4 feet above ground) or to trees where there are no other plants, including grass, growing under the tree. Where appropriate, spread recommended fertilizer uniformly on the surface under the branches. If grass or other plants are growing under the tree, it may be necessary to apply the fertilizer in 2 or 3 applications with thorough watering after each application.

Drill Hill Application: It is generally thought that larger shade trees require more fertilizer than surface applications can provide. Rates recommended for larger trees would stimulate excessive growth of ground covers and lawns and, if fertilization rates become high enough, toxic effects to groundcovers could occur. Also, University of Massachusetts research indicates that phosphate does not move downward in soil. Therefore, sub-surface placement of fertilizer using drill hole application is recommended. Use an auger, crowbar, or soil sampling tube to drill holes into the soil over tree roots. Holes should be 1-1 ½ inches in diameter, 12-18 inches deep and spaced about 2 feet apart arranged in concentric circles beginning 1 foot from the trunk and extending at least a foot or two beyond the spread of the branches. Distribute fertilizer uniformly among the holes using a funnel. Then fill the holes with topsoil or a soil amendment such as peat moss or perlite.

Shrubs

Fertilizers should be broadcast on the soil surface over the roots and watered in, between mid April and mid May.

Individual Specimen Shrubs: One-half to one pound 10-10-10 or equivalent per plant.

Groups of Shrubs: Two to four pounds 10-10-10 or equivalent per 100 square feet.

Hedges: Four pounds 10-10-10 or equivalent per 100 linear feet; one-half of the amount along each side of the hedge.

Broadleaf Evergreens: Two to four pounds 10-10-10 per 100 square feet. The amount may be split into two applications, one in early spring and the second after flowering. Organic fertilizers such as cottonseed meal, which contains nitrogen in the organic form, is satisfactory for fertilizing acid loving broadleaf evergreens. Apply organic fertilizers at a rate of 4-5 pounds per 100 square feet.

Last Updated: 
Apr 4, 2012
Topics: 
Home Lawn & Garden
Home Lawn and Garden topics: 
Cultural Practices/Fertilizing
Flowers
Fruit
Vegetables