Question of the Week
Answer: Poor soils for fruit plants can be those that are too rocky, clayey, poorly drained, too well drained (droughty), acid, and/or infertile. Luckily, there are remedies for almost all of these, and, once established, woody plants are often quite tolerant of these conditions. Read on for some simple ideas on how to deal with soil problems.
Adding organic matter helps break up clay soils, gives life to sandy and rocky soils, improves water absorption and retention, and adds nutrients. However, there can be too much of a good thing. When planting in a clay or rocky soil, for instance, if the grower fills the hole with too much organic matter, he or she can unwittingly be producing a situation like growing in a pot: the roots don't extend beyond the nice hole with all of the good soil and can even become tangled and "pot-bound." So, in a clay or rocky soil, no more than 25% of the backfill in the hole should be potting soil or compost or some other organic matter-rich material. You want to encourage the roots to extend out into the surrounding soil. Unlike a clay soil, it's hard to add too much organic matter to a sandy soil; the roots will easily extend into the sand.
You can also encourage the roots when first planting in a clay soil by making sure that the sides of the planting hole are not perfectly round and/or glazed. A typical shovel can glaze the sides of a hole dug in clay soil, but an auger is really bad for creating that condition. The simple remedy is to score or rough up the sides of the hole with your shovel and make sure you don't curl or bend the roots when placing the plant in the hole. It's better to prune back the roots a little than to bend them, but better yet would be to dig a square hole or otherwise provide channels for root extension. In other words, avoid root constriction.
Regarding drainage, there is internal drainage based on soil texture (clay, sand, and loam) and external drainage based on topography. Clay provides poor internal drainage; a very sandy soil can be too well-drained (droughty). A sandy loam soil is best for most fruit plants, though additions of organic matter make it better still. Our common red and orange clays are indicative of some soil oxygen as these colors are the result of iron oxides (rust) in the soil, so such soils can be used for planting and made better by adding organic matter and taking care during planting as described in the preceding paragraph. Black, white, and gray clays should be avoided altogether because they are usually too wet and, wet or dry, do not provide enough oxygen for plant roots; not much can be done with them for the purposes of fruit growing.
External drainage refers to the water flow over a piece of land. All fruit species adapted to the Ozarks are intolerant of standing water, so avoid boggy spots or areas where the water drains out too slowly. Stone fruits, like plums, peaches, and cherries, are especially intolerant of poorly drained conditions.
If the soil is excessively droughty because it's sandy and/or on a slope, provide a slightly raised berm on the downside of the hole to encourage the water to collect and drain out more slowly.
Acid soils (technically, anything below pH 7) are the norm in the Ozarks; in fact, undisturbed forest soils of the Ozarks are usually around pH 5.2 to 6.0. Fortunately, most fruit plants are tolerant to anything down to pH 5.7 or thereabouts. Blueberries require a highly acid soil (ideally between pH 4.8 to 5.2), so a blueberry grower might actually need to further acidify the soil with a sulfur-based product (but do it according to a soil test). Pears are generally fine with the native pH. Other fruit plants will usually do best in soils that are only slightly acidic (pH 6.0 to 6.5), but they are generally tolerant and can perform well enough in any soil from pH 5.8 to 7.2. The grower will need to have a soil test to ascertain soil pH. The remedy for an acid soil is agricultural-grade crushed limestone applied as per instructions that will come with your soil test results.
Soil samples can be submitted to your county Cooperative Extension office, or you can buy simple soil-testing kits online. Ozark soils are notoriously poor in nutrients, but most trees, including fruit trees, are not particularly demanding. Adding nutrients in elemental form, as in most commercial fertilizers, should be done in accordance with a soil test, but annual or semi-annual applications of compost and mulch on top of the soil (don't put any type of fertilizer in the planting hole) usually provide adequate fertility for home growers. Though technically not organic or "natural," products like Jobe's Tree and Fertilizer Spikes™ are safe and effective ways to provide season-long, slow-release nutrition to young fruit plants.
Past three years of age, most fruit plants do well enough on the fertility provided by decaying mulch and maybe a shovel or two of compost. If you detect nutrient deficiency symptoms like yellow leaves or stunted growth (fruit trees should put on a minimum of about 12 inches of new growth every year), increase applications of compost or winter applications of manure. If fertility issues seem pressing, consider quick-release fertilizers like compost tea or manure tea, fish emulsion, or non-organic liquid fertilizers like Miracle-Gro™.
For more information, consult the ATTRA publication Fruit Trees, Bushes, and Vines for Natural Growing in the Ozarks. This publication discusses how to overcome common challenges of growing fruit trees, vines, and bushes in the Ozarks and suggests what to look for when choosing a variety that will thrive locally.
Note: The mention of specific products or brand names is for educational purposes only and does not constitute endorsement by NCAT, ATTRA, or USDA.
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