Fertilizers and soils are a vital part of producing gardens and orchards. Soil tests are not necessary each year but are used if problems develop or when starting a new garden. Soil tests are available through Utah State University Extension Service offices in each county. A standard soil test costs $10 and tests the phosphorus and potassium levels as well as pH (acidity or alkalinity), salt levels, and lime (calcium). The test indicates which nutrients need to be added and if salt or soil pH may be causing problems with the plants. Standard soil tests do not check nitrogen levels. Nitrogen levels are continually changing and this nutrient is often leached away. Nitrogen recommendations are made on plant needs and not what remains in the soil from year to year.
Routine soil tests do not detect toxic chemicals or pesticide residues in the soil. Those tests are done by specialized laboratories and are very expensive. Soil tests do not indicate neglect, poor variety selections, excessive shade, weeds, diseases, insects or irrigation problems. Soil tests are not a cure but are a tool used in making decisions.Soil tests do indicate trends by area gardeners. One trend is a tendency to overuse some fertilizers. Each year, the Salt Lake County Extension office gets results of soil tests submitted through Utah Sate University. These tests indicate that many gardeners are oversupplying phosphorus. Over 30 percent of the tests show excessive amounts of phosphorus and or potassium. These tie up iron, zinc and other micronutrients and make it difficult to grow many plants. In some cases, however, more phosphorus is needed for heavy feeding plants such as potatoes and corn.
The problem with excessive phosphorus is there is no easy way to remove it from the soil. The only way to get it out once it is applied is to remove it through plant growth. Turfgrass uses only small amounts of phosphorus. Apply nutrients only when needed and don't over-apply as too much will damage plants.
Fruit trees should be fertilized within the next few weeks. Typically, fruit trees should receive fertilizers based on their growth of the previous year. Instead of looking at a chart to find how much fertilizer to put on your fruit trees this year, let the tree tell you. Look at the growth of the past season. The growth starts at the bud scale scar (annual growth ring) and extends to the tip. Last year's wood is usually a more intense color, either bright red or yellow, than the older wood. Two-year and older wood has developed a dull or grayish appearance.
Measure the length of the shoots from the previous years on several branches and determine an average length. The table on this page suggests the average length of shoot growth for healthy trees. Increase the amount of nitrogen fertilizer if the shoot growth is below average and decrease the rate if the growth is above average.
Pears frequently do best without added fertilizer because of the damage fireblight can cause to young vigorous growth. Apply the nitrogen in a band below the outer edge of the branches. For young trees, the width of the fertilizer band may be about 2 feet near the trunk. Mature trees should have a 2- or 3-foot wide band 8 to 10 feet away from the trunk. Nitrogen fertilizer applied in late winter or early spring gives the best results.
If you don't like measuring the limbs on your tree, the chart on this page gives some general guidelines.
Fruit tree fertilization is often misunderstood. Trees have an extensive perennial root system that allows them to absorb adequate nutrients. Iron is the most serious micronutrient problem. Trees that show problems should be treated early and not overwatered. This causes serious problems that are difficult to correct. Careful fertilization will give larger, higher quality fruits to enjoy this summer.
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(Additional information)
Average shoot growth in inches
Fruit tree Young trees Bearing trees
under 6 years over 6 years
Apple, dwarf, semidwarf 10-20 inches 4-8 inches
Apple, standard, spur types 10-20 inches 6-10 inches
Peach, nectarine, apricot 10-24 inches 8-15 inches
Sour cherry, plum 10-20 inches 8-12 inches
Pounds of nitrogen (per tree) for fruit trees
Age of Actual ammonium ammonium
tree nitrogen nitrate sulfate
1-3 years 1/4-1/2 lb. 3/4-11/2 lbs. 11/4-21/2 lbs.
3-8 years 1/2-1 lb. 1-12/3 lbs. 21/2-5 lbs.
Mature 1 minimum 3 minimum 5 minimum
Large
apple,
cherry 11/2-3 lbs. 41/2-9 lbs. 71/2-15 lbs.