GROWING ORNAMENTALS IN THE CLAY SOILS OF THE BLACK BELT
What kind of soil do I have?
Will I have problems with my soil?
How can I tell if my soil holds too much water?
How can I improve the percolation of my soil?
Does a perk test tell me all I need to know?
How can I adjust the pH of an acid soil?
How can I adjust the pH of an alkaline soil?
What can I grow in acid clay soils?
What can I grow in alkaline clay soils?
What kind of fertilizer is best?
How much fertilizer do I need?
How often do I water things in clay soils?
How do I plant things in clay soils?
What problems will I have gardening in black belt soils?
Soil is one of the most critical factors in determining what plants can be grown successfully in the landscape. The primary focus will be on the soils of the Black Belt but the principles outlined are applicable to any clay soil throughout Alabama.
Many plants are limited by the range of soils they can tolerate. Sandy soils can grow a much wider range of plants than clay soils in the same region. Generally, the more clay in the soil and specifically, the more alkaline the pH, the more problems there will be in growing plants successfully.
WHAT KIND OF SOIL DO I HAVE?
Many different kinds of people need to ask this question - engineers, architects, landscape architects, developers, contractors, home builders, and homeowners. The answers will affect property development, sanitary facility types and location, types of foundations for houses, and the suitability for ponds, roads, and recreational facilities.
To find out what kind of soil you have, take the legal description (Section and Township) of your parcel of land to the local Alabama Soil Conservation Service office. They have the Soil Survey books for each county. These books contain aerial photos of the entire county with the soil groups drawn in. The ASCS people can tell you exactly the name of the soil you have and for what it can and can not be used. However, for the purpose of growing plants, this is not enough. The clay soils of the Black Belt are highly variable in the different aspects that can affect plants. These clay soils can range from a pH of 3.5, which is too acid for most plants, to a pH of 8.4, which is too alkaline. Water can soak down less than one half inch per hour in some of the Black Belt soils and down to 20 inches per hour in others. They can have as little as 1/2% organic matter in the poorest soils, up to 7% organic matter in those considered more fertile. They can range in clay content from as low as 2% in some of the sandier soils to 85% clay in some of the alkaline soils. Some swell and shrink very little; others are some of the highest on the scale.
Because the variability is so great, even within a given soil series, just knowing the name is not that helpful. Whether it will cause plant problems or not is more important to the home gardener.
WILL I HAVE PROBLEMS WITH MY SOIL?
Just because the soil looks dark does not mean that it is good. Just looking will not tell you if you will have problems growing your favorite plants. Several tests are required. The amount of clay present in any soil has a great impact on landscape plants in central and south Alabama. Clay is not all bad. Clay particles are the savings account for minerals in the soils. Sandy soils can be very deficient in necessary minerals, and when they are added, there is nothing to hold on to them for very long. On the other hand, clay soils are rarely deficient and the nutrient status can be easily corrected before planting. Once they are corrected, they will stay corrected for some time.
The biggest problem with clay is the size of the particles. Clay particles are very small. In general, soil has three sizes of particles, or components - sand, silt and clay. To give an idea of their relative sizes - if an average clay particle was the size of a marble, then the size of an average silt particle would be about the size of a basketball. The average sand particle would then be about the size of a football stadium! The small size of a clay particle is really the source of the two biggest problems we have with Black Belt soils - they hold too much water and they do not have enough large air spaces. Both of these effect the health of a plant's roots.
HOW CAN I TELL IF MY SOIL HOLDS TOO MUCH WATER?
Do your own Perk Test
Some people are familiar with this test, but only as it relates to engineers and septic tanks. Every homeowner needs to do their own perk test. This test gives an idea of how fast water moves downward through the soil. This then tells us if there is a drainage problem with this soil. It also tells us how often we need to water newly planted plants.
Dig a hole about one foot square and one foot deep. Fill it up with water. Look at your watch and write down the time. Check it every hour, noting how many hours it takes for the water to completely drain away. (To be more accurate, as soon as the hole is empty, fill it again with water and start counting a second time. It should take longer the second time and will be more accurate).
If it takes less than 1 hour for the water to percolate down into the ground, there will be few problems in growing plants in this soil. However, this soil may be too sandy and not hold onto water or minerals long enough for optimum plant growth. It can be made better by rototilling in some organic matter to help hold more water. Some kind of irrigation system will probably be advisable to make the frequent waterings easier.
If it takes up to 2 hours to percolate into the ground, this soil has great percolation. There should be few problems in growing things.
If it takes more than 4 hours to percolate down into the ground, you can expect significant problems in growing plants, particularly during long wet spells. Most of our commonly used landscape plants can't take swamp conditions for very long periods. Under these conditions, the air spaces are filled with water. There is insufficient oxygen in the soil to support normal root function. A breakdown of tissue and a weakening of the root system occurs. Under water-logged conditions, root rot fungi populations build up in the soil. They are able to attack the weakened roots. The plant will wilt and the leaves will turn black. We say that the plant has drowned.
Most Black Belt soils have too much clay in them. The physical structure will have to be altered to obtain a more desirable percolation rate which will improve plant growth potentials.
HOW CAN I IMPROVE THE PERCOLATION OF MY SOIL?
To improve plant growth potentials, you have two choices. One is to improve the internal drainage of the soil. This is called amending the soil. The other is to build raised beds. In some instances, both practices are recommended.
When a clay soil is amended, the goal is to increase the size of the air spaces in these tight clay soils. There are many different things you can use for this purpose. For years, composted manures have been used, not for the nutrients, but for increasing the amount and size of the air spaces. Peat moss and composted leaves have also been used. Shredded pine bark is also appropriate and it comes in several sizes. Use the size that looks most like peat moss. All of these choices are organic sources of things that will increase the amount and size of the air spaces within; however, organic materials have another property that needs to be considered. In sandy soils, we add organic matter to hold moisture, which it does very well. Because of this, organic materials are broken down quickly by microbial activity. When that happens, they lose their effectiveness as amendments. This is a disadvantage of using organic materials to increase the amount and size of the air spaces within a soil. This can be offset, in general, by using inorganic materials instead. Sand has been used for years for this purpose. In some places, an agricultural grade of expanded shale rock can be purchased. Perlite accomplishes the same effect. But a word of caution about vermiculite: even though it is expanded mica, the fluffed up platelets will eventually compress back again. For this reason, vermiculite is not recommended as a permanent soil amendment.
In most instances, these materials are laid down on top of the ground and rototilled in. Research indicates that the perfect growing medium for most plants will contain 35% to 50% air spaces. This would be equal to a soil which is about 1/3 to ½ amending material. Rototillers work in the first 6 inches of the soil. For a half-and-half soil mixture, put down 3 inches of manure and rototill in. Then put down 3 inches of sand, and rototill it in. Adding this much organic and inorganic matter to a native soil will increase the soil volume. This makes building a raised bed all the easier.
DOES A PERK TEST TELL ME ALL I NEED TO KNOW?
No. The second most serious problem with Black Belt soils is their pH. This is a measure of how acid or alkaline the soil is. Black Belt soils can range in pH from 3.5 to 8.4. The pH of a soil effects a plant in either of two ways - by tying up various necessary minerals on the clay particles and making them unavailable to the plant or by causing some minerals to become so available in the soil solution as to become toxic. Soils which have a low pH (which are too acid) or a high pH (which are too alkaline) give plants lots of trouble. We have to know the pH of any soil we are planning to use so we can make the proper adjustments for optimum plant growth.
There are several different ways to determine the pH of your soil. A hand-held pH meter works fine if the cleaning instructions are followed very carefully before and after each use. The small home testing kits are quick and relatively accurate. The major limitation with both of these is that they tell only the pH and not how much of what has to be added to change it. In the long run, you get more useful information for the least amount of money by sending a soil sample to the Auburn University Soil Testing Laboratory. Your local County Extension Office has free supplies available for this purpose. The state partially subsidizes the cost of the analysis. There is a small charge to the individual. Refer to Circular ANR - 6 for information on how to take a soil sample.
Remember, the test is only as good as the sample you provide. Take many spoonfuls of soil from different spots around the yard. Be sure not to get any fertilizer grains with the soil. Mix the samples together in a bucket before filling up the box that is sent to Auburn.
The U.S. Soil Conservation Service uses the following scale to interpret the range of pH values that can appear on soil test reports. These categories relate to the effect of that pH range on plant growth, rather than to pure chemistry (where a pH of 7 is considered neutral).
Soils which are rated in the "Strongly acid" category will cause trouble to many plants, except azaleas and blueberries. Soils which are rated "Mildly alkaline" or higher will cause problems for many plants.
- <4.5 = Extremely acid
- 4.5–5.0 = Very strongly acid
- 5.1-5.5 = Strongly acid
- 5.6-6.0 = Moderately acid
- 6.1-6.5 = Slightly acid
- 6.6-7.3 = Neutral
- 7.4-7.8 = Mildly alkaline
- 7.9-8.4 = Moderately alkaline
- 8.5-9.0 = Strongly alkaline
- >9.0 = Very strongly alkaline
HOW CAN I ADJUST THE pH OF AN ACID SOIL?
This can be done most effectively before planting by rototilling in lime. How much lime to add (and which type to use) is specified on every soil test report. It is determined chemically. There is no other way to accurately tell just how much lime to add to any given soil. The amount of clay in a soil will effect the amount of lime needed to change the pH of a soil. Clay soils can require up to three times the amount of lime as sandy soils to change the pH one increment. The amount of lime specified on the report is a total amount. It may be applied any time of year and in several applications. It is not an annual amount.
All soils are buffered and resist a permanent pH change. With the use of acid forming fertilizers and acid rain, soils get more and more acid every year. In vegetable gardens, where lots of fertilizers are used every year, we recommend a soil test and the addition of lime every year. Otherwise, soil testing is recommended every 3-5 years.
Finely ground lime, mixed well in the soil, acts almost immediately to adjust the pH. If it can not be mixed in, it is another matter entirely! Placed on the surface of a lawn, the lime "moves down" about 1 inch in seven years. This is why, if at all possible, pH adjustments should be made before anything is planted. Certain horticultural enthusiasts want their beds at a precise pH value. It is practically impossible to be that precise. The pH values will vary slightly, according to the method used to determine them. Soils vary as to their response to lime, depending on their clay and organic matter content. This is why an optimum pH is generally expressed as a range, rather than a single number.
HOW CAN I ADJUST THE pH OF AN ALKALINE SOIL?
This is THE MOST FREQUENTLY ASKED QUESTION in Black Belt counties. If your soil pH is mildly alkaline (a pH of 7.4 to 7.8), sulfur is the preferred chemical to use to adjust the pH. Other products, such as ammonium sulfate and aluminum sulfate can be used, but their effect is not as long lasting. For the best results, these materials should be rototilled in before planting.
As with lime, up to three times the amount of an acidifying material is required in a clay soil to make the same pH change as in a sandy soil, depending on the amount of clay present. The effect is not permanent because soils are buffered, and tend to move back to their natural pH. Be careful not to apply too much sulfur at one time. Excessive sulfur can cause problems that are difficult to remedy. It is better to under-apply and check the pH periodically, rather than make one application.
For more alkaline soils, little can be done. Some Black Belt soils can be almost 1/3 lime by volume. The white lumps often seen in these soils are lumps of chalk, which is another name for lime. From a practical standpoint, this is too much lime to neutralize effectively. Although expensive, it is easier and more effective in the long run to replace alkaline Black Belt soil with good topsoil. Replacing soil is practical only for areas limited in size like the shrub and flower beds. It is not feasible for trees and is unnecessary for most lawn grasses.
WHAT CAN I GROW IN ACID CLAY SOILS?
In general, once the percolation rate is improved, an acid pH is easy to work with. This is because most landscape plants tolerate acid conditions better than alkaline conditions. On a moderately acid soil, you can grow almost anything the climate will allow. As a rule, that will be most things carried by the local garden center. Be sure to ask the garden center personnel to explain the requirements of any plants you are unfamiliar with.
WHAT CAN I GROW IN ALKALINE CLAY SOILS?
On alkaline clay soils, where the percolation rate has not been improved, the number of plants that do well is limited. As the pH value goes above 8, the number of choices decreases dramatically. At the higher pH values, many plants will become chlorotic (yellowing of the leaves) because of the tie-up of minor elements, particularly iron in the soil. Here are some plants that tolerate alkaline conditions:
TREES FOR ALKALINE SOILS Celtis laevigata (Hackberry) Cercis canadensis (Eastern redbud) Cercis reneformis 'Oklahoma' (Oklahoma redbud) Crataegus laevigata (English hawthorn) Fraxinus americana (White ash) Fraxinus pennsylvanica (Green ash) Ginkgo biloba (Ginkgo) Koelreuteria paniculata (Golden-rain tree) Lagerstroemia indica (Crape myrtle) Malus 'Profusion' (Crabapple) Pinus nigra (Austrian pine) Prunus (Japanese cherry) Quercus macrocarpa (Bur oak) Quercus muhlenbergii (Chinkapin oak) Quercus nigra (Water oak) Quercus virginiana (Live oak) Rhus typhina 'laciniata' (Cutleaf staghorn sumac) Thuja occidentalis (American arborvitae) Tilia cordata (Little-leaf linden) Taxodium distichum (Baldcypress) Ulmus parvifolia (Lacebark elm) . PLANTS FOR ALKALINE SOILS Acer negundo 'Variegatum' (Box elder) Achillea 'Gold Plate' (Yarrow) Achillea millefolium (Yarrow) Aesculus x carnea Alyssum saxatile (Gold Dust) Anemone blanda 'Mixed' (Windflower) Antirrhinum majus (Snapdragon) Artemisia arborescens Asclepias tuberosa (Butterfly weed) Aucuba japonica (Japanese aucuba) Buddleia davidii (Butterfly bush) Buxus microphylla japonica 'Wintergreen'
(Wintergreen Japanese boxwood)
Buxus sempervirens (Common boxwood) Buxus sempervirens 'Suffruticosa' (Edging boxwood) Campanula cochlearifolia (Bellflower) Campanula latifolia (Giant Bellflower) Canna Carpinus betulus (European hornbeam) Caryopteris x clandonensis Ceratostigma willmottianum (Hardy plumbago) Cercis siliquastrum (Judas tree) Chimonanthus praecox (Wintersweet) Chrysanthemum carinatum (Chrysanthemum) Chrysanthemum maximum (Shasta daisy) Convolvulus tricolor Coreopsis grandiflora (Bigflower coreopsis) Coreopsis tinctoria (Tick-seed) Coreopsis verticillata (Tick-seed) Cornus mas (Cornelian cherry) Cortaderia (Ornamental grass) Cosmos sulphureus (Yellow cosmos) Cotoneaster 'Hybridus Pendulus' Cotoneaster dammeri (Bearberry cotoneaster) Cotoneaster horizontalis (Rock cotoneaster) Crinum Crocus imperati Deutzia scabra (Fuzzy deutzia) Deutzia x rosea Dianthus chinensis (Chinese or Indian Pink) Dianthus x allwoodii (Pink) Dictamnus albus (Burning bush) Echinacea (Coneflower) Eleagnus pungens (Eleagnus) Euonymus alatus (Burning bush) Euonymus japonica (Evergreen euonymus) Fagus sylvatica (European beech) Forsythia x intermedia 'Lynwood' Fraxinus excelsior 'Pendula' (Weeping Ash) Gaillardia (Blanket flower) Gazania x hybrida Gypsophila elegans (Baby's breath) Hedera helix (English ivy) Helianthus annuus (Sunflower) Hibiscus moscheutos (Perennial hibiscus, Common rose-mallow) Hibiscus syriacus (Rose mallow or Tree hollyhock) Hyacinthus orientalis (Common hyacinth) Hypericum calycinum (Creeping St. Johnswort) Hypericum 'Hidcote' (St. John's Wort) Hypericum moseranum (Gold flower) Iberis umbellata (Candytuft) Ilex cornuta (Chinese hollies) Ilex vomitoria (Yaupon hollies) Iris (Tall bearded hybrid, Siberian iris,
Louisiana iris, Spuria iris, Dutch iris)
Iris reticulata Juniperus x media 'Pfitzerana Aurea' Kniphofia (Red hot poker) Lamium galeobdolon 'Variegatum' (Yellow archangel) Laurus nobilis (Sweet bay) Leucojum (Snowflake) Ligustrum japonicum (Japanese privet) Ligustrum ovalifolium 'Aureum' (California privet) Ligustrum sinense (Privet) Lonicera fragrantissima (Winter honeysuckle) Lycoris radiata (Spider lily) Lycoris squamigera (Magic or Surprise lily) Mahonia aquifolium (Oregon grape) Muscari botryoides 'Album' (Grape hyacinth) Myrica cerifera (Wax myrtle) Nandina domestica (Nandina) Nerium oleander (Oleander) Papaver orientale (Oriental poppy) Perovskia atriplicifolia (Russian sage) Philadelphus coronarius (Sweet mock orange) Phlox subulata (Thrift) Rosa hybrida (Hybrid tea roses) Rosmarinus officinalis (Rosemary) Rudbeckia (Coneflower) Salvia splendens (Scarlet sage) Salvia x superba (Salvia) Sambucus nigra 'Aurea' (American elderberry) Saponaria vaccaria (Soapwort) Saxifraga longifolia (Saxifrage) Scabiosa caucasica (Pincushion flower) Sedum x 'Autumn Joy' (Stonecrop) Silene coeli-rosa (Rose of Heaven) Spiraea x bumalda 'Anthony Waterer' (Bumalda spiraea) Stachys machrantha (Big betony) Syringa lacinata (Cut-leaf lilac) Thymus serpyllum (Wild thyme) Verbascum bombyciferum (Mullein) Verbena Vinca major 'Variegata' (Greater periwinkle) Vinca minor (Common periwinkle) Vitex agnus-castus (Chaste tree) Weigela florida Yucca filamentosa (Adam's needle) Grasses: Common and hybrid Bermuda, St. Augustine
WHAT KIND OF FERTILIZER IS BEST?
It depends on two things: the percolation rate, and the pH of your soil. If the percolation is poor, quick release nitrogen fertilizers, like ammonium nitrate, can be wasted. This can also have an adverse effect on the environment. During a heavy rain, too much nitrogen dissolves for the ground to fully absorb. Therefore it runs off into the storm sewer and gets into streams and ponds, and possibly drinking water sources. Nitrogen in drinking water can be very unsafe for us. Elevated levels in ponds and streams cause rapid growth of undesirable plants, like algae, that can clog and pollute these bodies of water.
If the clay soil is alkaline, there is another way to waste nitrogen. The ammonium nitrate in the quick release nitrogen types of fertilizer reacts with the lime in these clay soils, and as much as 1/3 of the nitrogen escapes into the air as ammonia gas. For this reason, slow release nitrogen types of fertilizers are more efficient on alkaline clays, because they don't use ammonium nitrate as their main source of nitrogen.
Two general fertilization strategies minimize nitrogen run off on clay soils. One strategy is to make monthly applications of a quick release nitrogen fertilizer at a low rate per application. The other is to use a slow release nitrogen fertilizer. Slow release fertilizers are generally more expensive than others but only need to be used once or twice per growing season. By slowly releasing nitrogen, they minimize run off and increase the chances of absorption by the clay soils. Because these clay soils are highly eroded, they sometimes can be deficient in other elements essential for plant growth. A soil test is recommended to check for several of these nutrient levels and will report exactly how much of each nutrient element is needed to bring the soil up to levels adequate for good plant growth. In general, nutrient deficiencies can be corrected by using a complete fertilizer like 13-13-13. After several years, additional phosphorus, potassium and magnesium will not be required and a complete or balanced fertilizer is no longer needed.
HOW MUCH FERTILIZER DO I NEED?
Because the levels of nitrogen are so variable throughout the year, the Soil Testing Lab does not test for this. The amounts of nitrogen recommended on a soil test report have been determined by ongoing field research that began in the 1920's. The amounts that are recommended on the soil test represent the cost effective levels - the most amount of growth for the least amount of nitrogen. Exceeding these amounts is not cost effective and can be harmful to the plant and our environment.
The pH of the soil also affects the amount of fertilizer used, particularly when fast release fertilizers are used. When ammonium nitrate is broadcast over wet, highly alkaline soils, up to one third of the nitrogen will be lost to the atmosphere as ammonia gas because of a chemical reaction. This reaction requires that an increased amount of fast release fertilizers will be needed to accomplish the same effect on an acid soil. Slow release fertilizers seem to be unaffected by alkaline soils.
Tight soils, ones with a poor percolation rate, also affect the amount of fertilizer to use because of their bathtub effect. Caution must be taken when fertilizing large plant materials that have been planted in the ground. Just as the water accumulates in the hole and threatens to drown the plant, so too does the dissolved fertilizer. Since it is not draining away, it continues to build up around the roots. To avoid a salting effect, transplanted trees need to be fertilized sparingly.
Routine fertilization of the landscape should be replaced by a low environmental impact approach to soil management, which would minimize the negative effect of nitrogen runoff on our water resources. This approach would have two phases. The first phase would stress building up the basic level of nutrients in the soils. Once adequate levels are reached, this approach would shift to applying amounts of nitrogen adequate to maintain an even foliage color, but not stimulate excess growth. This second phase would have to take into account the needs of different types of plant materials in different stages of development.
Research indicates that trees are very efficient at getting all the elements they need to grow for years. However, they also respond well to additional nitrogen. In general, if the lawn is fertilized, the trees benefit to such a degree that additional fertilizer is unnecessary.
Shrub fertilization should be approached in two phases. When shrubs are young and more growth is desired, more frequent applications of nitrogen are needed. A new landscape should be fertilized two times a season with a slow release nitrogen source fertilizer.
However, once shrubs have reached their mature size or a size at which they can be maintained easily, continued fertilizing only increases the need for pruning. More and more landfills are refusing to accept yard waste and disposing of the trimmings will become difficult and/or expensive. It is more environmentally sound to reduce fertilizer input to minimum maintenance levels that would maintain a good green color, but not stimulate unwanted growth.
Lawn grasses can survive with low rates of nitrogen. If a better green color is desired, slow release nitrogen fertilizers can be used. Grass provided with minimum nitrogen levels will require less frequent mowing.HOW OFTEN DO I WATER THINGS IN CLAY SOILS?
The frequency with which you water corresponds to your perk test results. To apply more water before all has had time to drain away will cause the hole to fill up with water and the plant to drown.
Your finger is an acceptable instrument for use in determining if a plant needs water. The soil should feel damp but not wet. A perk test will provide a more reliable test for determining how often you will need to water to reach greater depths. As a general rule, plants need about 1 inch of water per week to maintain active growth. This is assuming that the soil is sandy enough to absorb all the water that falls on it. With most clay soils, this is far from the case, so that it is not easy to know how long to leave the sprinkler on to get the affect of that 1 inch of irrigation.
HOW DO I PLANT THINGS IN CLAY SOILS?
When it comes to planting things in the clay soils of the Black Belt, you can not always plant them "by the book." The books say to plant the plant at the same level it grew before; but this is assuming the soil has a good percolation rate. In poorly drained clay soils, this can be bad advice and lead to drowned plants.
When dealing with heavy clay soils, it is important to remember the "bathtub effect". No matter how big a hole is dug, you still have a bathtub with no drain. No amount of gravel in the bottom of the hole is going to correct poor percolation. Therefore, certain steps can be taken to assure more successful transplanting.
One thing that can be done on certain sites is to place drainage tiles or slotted pipes in the bottom of the beds after they are dug and before refilling the beds. These pipes are run out to a storm sewer or ditch to allow the excess water to drain away. Care must also be taken to keep these very fine clay soils from washing into these pipes and eventually clogging them up. To do this, an acrylic type fabric is placed over these pipes before refilling with soil. This serves to filter out the fine particles. This whole process is expensive and generally successful, but can only be done where you have enough fall in elevation to do so. On level land other steps must be taken.
One thing-that is commonly done is to discard the soil taken from the hole and replace it with a good, sandy loam topsoil. While this seems to be an easy solution, this can cause problems later on. When the roots eventually fill this space and are forced to venture out into alkaline clay, chlorosis will occur. If the holes are larger, the problem is delayed. The major disadvantage with this is that there is a very great difference between the two types of soil. The looser soil tends to dry out much faster than the surrounding soil and the water in the surrounding soil will not move into the hole to keep the plant from drying out.
Fewer problems will be encountered if some of the discarded soil is mixed in with the replacement soil. This reduces the difference between the two soils. Sometimes a special planting mix can be purchased from garden centers. Either way, you should mix them on a one to one basis.
Another thing that can be done is to plant everything on raised mounds, 6-8 inches higher than the surrounding grade. This insures that the crown of the plant will not be submerged under water. Roots can tolerate standing in water much better than the crown. The crown is the part of the trunk, right at the ground line, where root tissue changes over into stem tissue.
Many people find it more feasible to build raised beds or berms, with good topsoil and not try to modify the percolation rate of the existing clay soil. This has its advantages. The most common disadvantage concerns watering things planted above ground. Above ground beds will need a lot of water. There are several types of drip irrigation and soaker hoses that can be installed at planting which greatly assist in overcoming this problem.
Another solution is to excavate about a foot of soil and discard it before building a raised bed or berm with good sandy loam. In this situation, the bathtub effect works to your advantage, much like a saucer holding excess water that moves back up into the flower pot and keeps it from needing water for a longer time. Beds built this way do not need to be watered as often.
One further problem is encountered because of the bathtub effect, particularly with large plant materials. It is very easy to over fertilize newly planted trees. Since the water is not draining out of the hole, neither does the fertilizer and a build up occurs. Planting is raised beds or on berms minimizes this problem.
WHAT PROBLEMS WILL I HAVE GARDENING ON BLACK BELT SOILS?
There are several physiological problems that are common in the Black Belt area of our state. The most commonly encountered symptom of a problem is chlorotic or yellowing leaves. This yellowing usually occurs between the veins of the leaves. Chlorosis occurs in plants growing in soils with a higher pH range. It can affect new or old leaves, the whole plant or just certain portions of the plant. It does not always appear as classic deficiency symptoms in its appearance. A long term effect on trees is a progressive stunting of the new growth which gives the tree a flat-headed appearance.
The most dramatic effect of alkaline conditions occurs on pine trees. They become very yellow. Most of the needles drop off and they continue to look sickly for years. Unfortunately, when it comes to trees, there is little that can be done to correct this condition. Applying acidification materials and/or extra nitrogen fertilizer can mask the symptoms temporarily, but does not correct the situation. Eventually you will become tired of the way the tree looks and cut it down.
Growing plants successfully in the Black Belt can be a challenge. It requires that you understand the uniqueness of the soils and climate of the region and then adopt practices that promote success.
IF YOU NEED HELP:
If you have additional questions, you can call your local County Extension Agent.