It's a real treat to go outside in the fall and pick a fresh apple off of your own apple tree. Growing an apple tree can be very rewarding, but also challenging at times. The apple gardener must be vigilant about insect and fungus problems. Important to mitigating these problems is good soil culture. Gardeners with clay soil will have to pay particular attention to establishing and maintaining proper soil for healthy apple trees.
Apple trees require well-drained, loamy soil containing adequate amounts of organic matter. Contrary to these needs, clay is both inorganic and very water-retaining. When apple tree roots sit in soggy soil the tree begins to decline, followed by death in severe circumstances.
Ideal soil for apple trees should contain adequate amounts of organic matter for the transfer of nutrients to plant roots. While organic matter is moisture-retaining, it also lightens up clay to provide drainage. Loamy soil rich in organic matter also aerates the soil which is good for roots.
Soil pH for apples trees should be about 6.5. Clay soils are often acidic. The right pH enables nutrients in the soil to be taken in by plant roots. Nutrient deficiency in apple trees can happen even when nutrients are present in the soil. Correcting pH makes major nutrients like nitrogen and potassium, as well as micronutrients like iron and magnesium, available.
At planting, amend clay soils with adequate amounts of compost or composted manure. One-third should be adequate. In very heavy clay, add another one-quarter to one-third sand to improve drainage. Soil pH should be adjusted with pulverized limestone (lime) or dolomitic limestone (dolomite) for acidic soils. The adequate addition of compost should moderate most alkaline soils. Clay soils often naturally contain nutrients such as iron, magnesium and manganese. Always apply pH and nutrient supplements according the results of a soil test, which will determine the specific needs of your soil.
Maintain apple tree soils by replenishing mulch which adds organic matter to the soil as it breaks down. Fertilize apple trees regularly to improve fertility. Adjust soil pH only as a soil test determines the need.