Fruit and Nut Review

Fertilizing and Irrigating

Applying fertilizer to fruit trees is essential to maintain adequate tree growth and good fruit production. Insufficient amounts of fertilizer result in a decrease in tree vigor, fruiting intensity, and fruit quality. Excessive amounts of fertilizer may mean a loss of fruit quality, primarily due to shading and poor spray coverage from the lush growth.

Before planting fruit trees, take a soil sample to determine soil pH and phosphorus and potassium levels in the soil. Fruit trees perform best at a soil pH of 6.0 to 6.5. If soil test results indicate a need for lime or phosphorus, apply these materials before planting the tree. Take additional soil tests every fourth or fifth year on established trees.

In most situations, fertilize fruit trees every year, including the year of planting. For the year of planting, apply fertilizer in early summer after the trees are set. For established trees, apply fertilizers about one month before start of growth in spring.

With newly-set trees, do not apply fertilizers within 10-12 inches of the trunk. For established trees, apply fertilizers under the tree, from close to the trunk to the drip line (outer edge of the branches).

Generally, you should broadcast fertilizer on the soil surface where rainfall or supplemental watering will aid in getting it into the soil.

Fertilizer rates depend on the type of tree, vigor, last year's growth and fruiting, and the ground cover under and around the tree. For most fruit trees grown in sod (except pears), use a basic rate of 0.1 pound actual nitrogen per year of tree age. Level off rates at about the sixth to seventh year. When tree age is not known, use a basic rate of 0.1 pound actual nitrogen per inch of trunk diameter measured one foot above ground. Level off rates at 0.6 to 0.7 pound actual nitrogen. Although fertilizer materials other than nitrogen may be needed, recommendations are based on nitrogen since it is the element found to be most frequently growth-limiting. Fertilize pear trees at half the basic rate.

The basic fertilizer rate may need to be adjusted up or down, depending on growth and fruiting of the tree the previous year. If trees are making less growth than indicated by Table 1, fertilize heavier than the basic rate. If tree growth is excessive, reduce the basic rate to try to bring growth back into desirable limits. The following table indicates the optimum growth rates for various types of fruit trees.

Table 1. Desirable growth ranges for fruit trees.

Drip irrigation systems have brought to the homeowner ways to irrigate several plants with a relative low volume water source. Drip irrigation is a point-source watering system; only the plants receive the water needed (instead of the whole garden or yard). Irrigation can result in higher quality fruit and vegetables and the overall health of the plant.

Drip irrigation comes in two forms. Emitters are point-source watering devices that are plugged into a polyethylene pipe and drip at the rate of 1/2 to 2 gallons per hour. Emitters are usually used in plantings where there are a few feet between plants, e.g., fruit trees, berry plantings, or perennial plantings around the house.

The other type of system is a drip tape, a small garbage-bag-like hose with tiny holes and drips water at 1/2 to 5 gallons per minute per 100 feet of tape. The drip hose is usually used for rows or plantings, like peas or corn, and discarded after one or maybe two years of use.

Drip irrigation also makes it easier to maintain a good, consistent water supply to the plants. Irrigating with small amounts of water daily (or every other day) is the best to get optimum plant growth.

A drip irrigation system is frequently installed before planting the home orchard and may be practical only when an overall plan is established. The basic system includes a water source, filter, pressure regulator, pressure gauge, cutoff valve, main line, and the drip lines. Filtration is needed to prevent plugging of the emitters or drip tape because of the very small openings where the water comes out.

The main line can be pvc pipe or flexible tubing directly off the water source to the drip lines (buried or above ground). The drip lines can also be buried or above ground, with the emitters above ground at the drip line of the plant or about 6 inches from the base of the plant when it is small. In the case of small trees, the emitter will be 6 to 8 inches away from the base of the plant in the beginning, and then additional emitters are added as the plant demand for water increases with size of the plant.

Frequency of irrigation may depend on the total volume of water available. Small trees and shrub-type plants should be irrigated no more frequently than daily up to every third day. When irrigation occurs every day or less frequently, apply enough water to carry the plant for the entire time until the next irrigation. Most plant use will be in gallons per day per plant or in inches per day. One square foot of water 1 inch deep is 0.6 gallon; one square foot of water 0.25 inches deep is 0.15 gallon. The area of the ground that is shaded by the plant can be calculated. To calculate the water use for plants on a daily basis, use the following formulas:

• Plants over 4 feet in diameter:

  gal/day = 0.125 X area

   

• Plants less than 4 feet in diameter:

  gal/day = 0.17 X area

When planning a drip irrigation system, remember fruit trees should be irrigated according to their water needs and the soil type. A 1-year-old tree usually requires 1 gallon of water per day. If the soil is sandy and the temperature, wind, and sunlight intensity are high, the tree could use 2 gallons per day and more frequent irrigation during these periods.

Excessive watering with any irrigation system can occur if the soil has a high clay content or does not drain well. Overirrigation can cause as many problems with growth as does drought.

A 2-year-old tree usually needs about 2 gallons per day and a 3-year-old tree as much as 4 gallons per day. Daily management and a good growing environment are two of the most important factors that influence water needs of plants.

Continue to irrigate trees, vines, and shrubs even after fruit is harvested. Control plant growth by limiting the amount of fertilizer applied.

Varying: PET 0.20-0.30'' per day and plant factors 0.6-0.8

By Dr. Freddie Rasberry, Extension Horticulturist, and James G. Thomas, Leader, Extension Agricultural Engineering

Mississippi State University does not discriminate on the basis of race, color, religion, national origin, sex, age, disability, or veteran status.

Information Sheet 1449
Extension Service of Mississippi State University, cooperating with U.S. Department of Agriculture. Published in furtherance of Acts of Congress, May 8 and June 30, 1914. Ronald A. Brown, Director

Copyright by Mississippi State University. All rights reserved.

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