By John Green, Certified Texas Expert Gardener, Orange TX
There are numerous types of soil amendments which can benefit garden soil. It is critically important for gardeners to know which amendment is needed before arbitrarily adding enhancers. Too much of an amendment can be detrimental to plants, negatively impacting soil health and the growing environment (image: thepsruce.com)
Colder weather continues ‘lingering’ in our area and will be around for at least two more weeks according to several 30-day weather forecast sites! Spring could be near at hand, as a couple extended weather predictors have balmy weather returning (mid-60’s) at the beginning of February. While I’m looking forward to spring’s return, it is a bit too soon for me to declare spring has arrived but welcome news when realized!
Most gardeners are well-acquainted with SETX clay soil structure and realize it is not optimum for plant health and growth which is often difficult to cultivate. Clay soil is challenging for gardeners and plants. Heavy clay soil drains slowly, retains moisture longer and once completely dry, becomes hard and brittle displaying fissures on a cracked surface. Specifically, our soil type is known as Coast Prairie Soil.
Adding amendments to soil “improves” soil in a variety of ways. Gardeners need to understand that the success of a plant is not simply dependent on its own health but also the quality of the growing environment. We now have more information available and need to educate ourselves as one aspect of soil conditioning has been gaining traction over the past several years. To create the most optimal growing environment for plants, are you taking advantage of it?
Soil amendment (aka conditioners) objective is to replace depleted (missing) macro and micronutrients, increasing nutrient availability, building soil structure to retain moisture. Soil rapidly becomes depleted after successive seasonal plantings unless amendments are continually added throughout the seasons. Some gardeners believe adding improvements once or twice a year is adequate (it might be adequate), though it would depend on the demands required of the soil! For example, vegetable gardens which are in constant production require additional amendments more frequently to maintain soil health between and during growing seasons to satisfy the nutritional needs of plantings. Conversely, many flower beds need two amendment cycles- before spring blooming and again in fall.
The goal is to support plant health and growth. Soil amendments can affect moisture retention, plant health, macro and micronutrient levels, pH, and much more. It is important for gardeners to note that having a soil analysis performed is an important step and a useful tool for gardeners, providing information such as macro and micronutrient availability, structure, pH, and more. Reach out to the local county extension office for more detailed information, and how to submit soil samples for analysis. The soil lab will send a report which provides detailed information on how to improve the soil. The information is valuable and required before adding amendments, other than mulch as top-dressing for moisture retention and weed control.
Where do we begin? Which soil amendments are needed? How much is needed? Building quality soil is a process which takes time! The process must begin with a soil analysis (the crucial “first step”) to improving clay soil. The lab report will provide gardeners with the exact amount of needed or missing nutrients to ‘build’ the best growing environment for healthy plants. Listed are several soil enhancers which can aid in transforming heavy clay soil into plant-friendly growing medium.
Organic Matter– helps to improve drainage and soil structure by lightening heavy clay soil. It provides beneficial nutrients allowing microorganisms within the soil to feed which improves the soil. Adding aged manure and compost is typically added spring before planting. This is accomplished by incorporating a 2 to 3-inch layer of the amendment, then working into the soil at shovel depth. FYI- this gardener continues adding organic matter throughout the growing seasons using shredded leaves, grass clippings, including additional composted manure. Compost is a source for soil microbes such as bacteria and certain fungi.
Raised Beds- building elevated structures or raised beds can increase drainage. Raised beds can take many forms from simple mounds of soil such as is used in a conventional vegetable garden, or it can be elevated from ground level and constructed of wood, brick, stone, or other materials. When constructing a raised bed, ensure the bed’s size (width) is such that gardeners can reach the middle from either side. It is important to note that if a raised bed is utilized, do not use soil from the landscape, as this will defeat the purpose of building the raised bed. Added soil must be of good quality, such as a combination of purchased garden soil, compost, and aged manure.
Mulch Beds- always! Never allow beds to remain bare… as rain will compact the soil making it more difficult to work the soil in spring. Any mulch will work! Mulching keeps weed growth to a minimum during winter. In spring, remove the mulch by placing it on garden paths, as it may not have decomposed enough to be worked into the soil.
Expanded Shale- a common sedimentary rock that comprises of flakes of clay and other minerals such as quartz and calcite. Expanded shale is also found in Texas, from a time when Texas was an enormous lakebed. It is lightweight, gray, porous gravel and closely related to perlite and vermiculite. By adding it to heavy clay soil, it lightens and aerates the soil but can hold 40% of its weight in water. Note expanded shale does not break down readily, meaning clay soil will remain friable many years once incorporated.
Greensand– is an organic fertilizer containing mineral deposits from the ocean floor. It enhances soil structure, allowing for increased root growth and excellent for overall plant health by providing needed nutrients. Greensand isn’t water soluble, so it needs to be incorporated into the soil at a rate of 30lbs per 1000 feet.
Amendments…Continued
Fertilizers- provide plants nutrients and can come in many forms: soluble salts, manure, peat or compost.
Lime- elevates the soil’s pH level, making it less acidic.
Gypsum- is a soft mineral that improves aeration of compacted soil which allows soil to drain more effectively.
Sphagnum Peat Moss- absorbs water, slowly releasing to the plants root for use. It provides aeration, lightening clay soil, and adds mass to sandy soil which helps prevent the loss of important nutrients.
‘New’ Amendment
Mycorrhizal fungi is a soil amendment which in my opinion is under used! It is a beneficial fungus which other plants have been coexisting harmoniously since the beginning of time. Mycorrhizal fungi colonize the plant’s root system and develops a symbiotic relationship with the plant. The fungi’s filaments (fibrous structures) allow the plant to draw nutrients and extract water from the soil which the root system is not able to access otherwise. The fungi excrete enzymes breaking down soil particles (organic matter) into nutrients readily accessible to plants. The fungi (in return) receive sugars, and other nutrients of their own from the plant.
Improving nutrient availability and water absorption enhances a plant’s root systems, which in turn improves a plant’s survival, flowering, production, and harvest. Mycorrhizae dramatically increase the effectiveness of traditional soil amendments!
Until next time fellow gardeners, let’s go out and ‘amend’ ourselves a greener and more sustainable world, one plant at a time! Please send your gardening questions to: jongreene57@gmail.com.
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