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Clay Soil

Help, I thought clay was for molding and making pottery and facial masks, but alas I seem to have an entire yard of clay soil and what do I do for planting since I am not a potter and I am a burley guy with whickers that does not require a facial mask.

- Ed in Prescott Valley

Ed, it sounds like you are really bogged down in the clay soil and we know that can be a challenge for planting. Clay soil, the dense, cloudy and sticky clay makes planting a trail in patience. To make you feel a little better, there are some ornamentals that thrive in clay soils. Clay soils to after all retain a great deal of nutrients along with the water they hold. However, the majority of annual and perennial plants are not tough enough to survive clay because the clay is so dense it holds little oxygen and will not allow the roots to breathe. Your spring flowering bulbs will not have a chance as they will not overwinter without rotting in the clay soil. For those of you that are not as much in the know about clay soil as Ed seems to be, clay is characterized by its tendency to clod and stick to your garden tools and almost impossible to shovel out of the ground. Heavy clay soils are approximately a 50/50 ratio of clay to soil. All is not lost if you are working with clay soil. It is still possible to create a flowerbed in a clay soil area; it just requires a little more effort and management. The best way to amend clay soil is to mix it with other matter that will make working with it easier and this will also increase the flow of oxygen and promote proper drainage. Here are some helpful hints to working with clay soils. Organic amendments are well suited to modify clay soils. Many of our landscapers prefer organic corrections to clay soil because they believe that organics offer long-term benefits and help establish plants quickly and organics work well to loosen up soils and improve the soil structure. Types of organic material include decomposed plant materials such as grass clippings, kitchen vegetable scraps, and shredded leaves. All of these materials should be well decomposed. Please read our article of a few weeks back on how to create compost using these very items. The improved soil condition will remain long after the organic composted material has disappeared. To incorporate organics into soil, break up approximately the top 8 to 12 inches of soil in the area you are working in. (Do not remove this soil from the area; you are going to add to it) Then add approximately 2 inches of organic material to the soil. When this is mixed then add another 2 inches of organic material and again, mix well and work together. Do this one more time as the final layer. Once you have finished, your bed/planting area will be several inches higher. but it will settle down over time. Keep in mind, this higher planting/bed area will facilitate drainage. You can use what they call inorganic soil corrections such as gravel and sand, but these are not recommended. Sand is the only useful material for breaking up clay, however it must be used in very large quantities often in excess of 50 to 60 percent of the total volume, and if not used correctly or the mix is off, you can create a clay pack that will be even denser than before you started. Gravel can work well to loosen clay and it works well to promote drainage and add oxygen, but it does not provide any nutrients to the plants. So if you add gravel, you must add fertilizer and also organic material. Keep in mind, no matter which soil amendment you select, you should never work the bedding area if the clay area is wet. Amended clay soils areas benefit from smaller more frequent irrigation. Clay soils, even with the addition of amendments will never be an ideal soil for plantings. They can only be improved. Many of you have probably heard about adding gypsum to your clay soils for improvement. Gypsum should only be used if your soil is affectionately called SODIC. Chemistry 101 – SODIC soils have high levels of exchangeable sodium and low levels of total salts. SODIC soils are hard, cloddy and at times they appear to be crusty. The addition of gypsum will not improve clay soils unless the soil is also SODIC. Gypsum has the ability to penetrate clay (fine clay particles) and will add moisture air pockets that will over time loosen up the clay soil structure. You must have patience for this type of application. It does not happen over night, but takes several years, with yearly applications of gypsum to the soil. Gypsum can eventually improve your soil. If you are attempting to plant and amend a larger clay soils area, it might be more beneficial and cost effective to prepare the bed all at one time. If you need only a smaller area for potted plants and accent plants, you should consider purchasing potted soil mixtures to use in the clay area.

Phone: (928) 778-0040


810 E. Sheldon Street, Prescott, AZ 86301

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