University of Maryland Extension

Fertilizer - Organic/Inorganic - Fruits

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Fertilization is important for all fruit crops. Where the levels of one or more of the critical nutrients—nitrogen, phosphorus, and potassium—are below those required for good growth and maintenance of the crop, plants become stressed and produce fruit of poor quality. Plants under severe nutrient stress often decline and can be predisposed to certain diseases and insect pests that will eventually kill them. Conversely, overfertilization, regardless of the nutrient source, can produce weak growth, prone to attack by diseases and sap sucking insect pests.

Although too much fertilizer can be toxic to plants, most of the excessive amount is wasted. Excess is carried away by ground and surface water and can contaminate streams, lakes, and the Chesapeake Bay.

Small fruits are not heavy nutrient users, but timely applications of fertilizers will be essential. Be careful not to burn foliage with liquid or granular fertilizers. Keep fertilizers 8 to 12 inches from crowns.

Organic fertilizers. All fruit trees and plants benefit from the generous mixing of organic matter with soil prior to planting. Organic matter enhances root growth, provides a wide range of nutrients and increases the soil’s water-holding capacity. Many organic gardeners grow successful backyard fruit crops by relying entirely on sources of organic matter for necessary plant nutrients.

Organic fertilizers, such as composts, blood meal, and fish meal, can be substituted for chemical fertilizers in home fruit plantings. Composts made from manures or yard waste should be fully decomposed and aged for at least 6 months before it is used around fruit plants. Fresh manure can carry human pathogens and burn plant roots due to the high salt content (especially poultry manure). Foliar applications of seaweed extract, compost tea, or fish emulsion are also beneficial organic fertilizers and work best when applied in early spring when new growth starts, at bloom, and at fruit set.

Organic fertilizers are generally lower in major nutrients, more expensive, less consistent in nutrient content, and bulkier than chemical fertilizers. But they have the advantage of providing many essential nutrients to plants, at a slow rate over an entire growing season, and are less likely to burn plant roots or foliage. Because the mineral nutrients in organic fertilizers are still bound in various organic products, these fertilizers should be applied in the late fall to early winter so that biological decomposition can occur before these elements are needed in the spring.


Inorganic fertilizers. The advantage of inorganic fertilizers is that relatively small quantities are needed and the exact amount of nutrients applied is known and adjustable. Complete inorganic fertilizers contain all three major nutrients—nitrogen, phosphorus, and potassium—and are labeled with the percent by weight of each nutrient. Thus, a 10-6-4 fertilizer contains 10, 6, and 4 percent nitrogen, phosphorus, and potassium, respectively. In the home garden, a balanced 10-10-10 fertilizer is one of the most versatile. Because the nitrogen, phosphorus, and potassium in inorganic fertilizers is in a form that can be readily absorbed by plant roots, these materials can be applied in the early spring. This ready availability is a disadvantage in that, at excessive rates, foliar burn may occur.  Fertilizers applied in the fall or winter risk the chance of being leached down through the rooting zone before they can be utilized. Late summer and early fall fertilization can also interfere with the plant’s ability to harden off for the winter and encourage succulent late growth that is easily killed in winter.

After planting, fruit crops should be fertilized each spring, unless they are grown adjacent to turf that is regularly fertilized or are making excessive leaf and shoot growth.

A good rule of thumb is to apply 1 pound of 10-10-10 fertilizer per 100 square feet (10 feet by 10 feet) of soil each year. This should give fruit plants good green leaf color and allow moderate plant growth and fruit development. Remember that excessive applications of fertilizer can reduce both the yield and quality of fruit and, in some instances, make plants more susceptible to disease and to winter injury. Apple trees that produce 12-18 inches of new shoot growth each year do not need to be fertilized. Keep in mind that fertilizers applied when conditions are dry are not available to the plant; if adequate rainfall does not occur, make sure newly fertilized plants receive adequate water to ensure the availability of nutrients in the rooting zone.

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