Improving Soil Health
Though some gardeners are fortunate to have excellent soil, the majority of us have less-than-ideal soil. Don't be discouraged if your soil contains too much clay, is too sandy, stony, or acidic. Once you grasp the components of good soil, it is not difficult to transform bad soil into plant-friendly soil.
Soil is made up of weathered rock and organic materials, as well as water and air. The organisms—small animals, worms, insects, and microbes—that thrive when the other soil components are in balance constitute the hidden "magic" in good soil.
Minerals. Approximately half of the soil in your garden is made up of tiny pieces of weathered rock that have been gradually broken down by the forces of wind, rain, freezing, and thawing, and other chemical and biological processes.
Soil type is typically characterized by the size of these inorganic soil particles: sand (big particles), silt (medium-sized particles), or clay (very small particles). The mixture of sand, silt, and clay particles in your soil defines its texture and determines drainage and nutrient availability, which affects how well your plants develop.
Organic Substance. Organic matter refers to the partially decomposed remains of soil organisms and plant life, such as lichens and mosses, grasses and leaves, trees, and all other types of vegetative matter.
Organic matter is vital, even though it constitutes just a tiny portion of the soil (about 5 to 10%). It binds soil particles together to form porous crumbs or granules that enable air and water to flow through the soil.
Organic matter may absorb and store nutrients as well as retain moisture (humus may contain up to 90% of its weight in water). Above all, organic matter provides food for bacteria and other kinds of soil life.
Compost, aged animal manures, green manures (cover crops), mulches, or peat moss can all be used to enhance the quantity of organic matter in your soil. Concentrate on the top 6 inches of soil since it contains the majority of soil life and plant roots. Read All About Composting for additional information on how to make your own compost.
Be careful when adding significant volumes of high-carbon material (straw, leaves, wood chips, and sawdust). In their attempt to digest these items, soil microbes will use a lot of nitrogen, potentially depriving your plants of nitrogen in the short run.
Life in the Soil. Bacteria and fungus, protozoa and nematodes, mites, springtails, earthworms, and other small animals can all be found in good soil. These microorganisms are required for plant development. They aid in the conversion of organic materials and soil minerals into vitamins, hormones, disease-fighting chemicals, and nutrients required by plants.
Their excretions also assist in the formation of tiny aggregates of soil particles, which cause the soil to be loose and crumbly. It is your responsibility as a gardener to establish the optimum circumstances for these soil creatures to do their work.
This implies that supplying them with a sufficient source of food (carbohydrates in organic matter), oxygen (found in a well-aerated soil), and water (an adequate but not excessive amount).
Air. Healthy soil contains around 25% air. This much air is required for the survival of insects, bacteria, earthworms, and soil life. The air in the soil is also a significant source of atmospheric nitrogen, which plants use.
Pore space between soil particles or crumbs is abundant in well-aerated soil. Fine soil particles (clay or silt) contain very small gaps between them, in some cases too small for air to get through. Soil made up of large particles, such as sand, has huge pore spaces and lots of air. However, too much air might cause biological materials to degrade too rapidly.
Add enough organic matter to your soil to maintain a balanced supply of air, avoid stepping in the growing beds or compacting the soil with heavy equipment, and never work the soil while it is extremely wet.
Water. Water makes up around 25% of healthy soil. Water, like air, is retained between soil particles in the pore spaces. Rain and irrigation water may flow down to the root zone and into the subsoil because the pore spaces are large.
The gaps between soil particles in sandy soils are so wide that gravity forces water to flow down and out extremely rapidly. That is why sandy soils dry out so quickly.
Water can migrate back up through the capillary action mechanism because the pore spaces are small. Water has filled the pore spaces of waterlogged soils, pushing all of the air out. This suffocates both soil microbes and plant roots.
Your soil should ideally contain a mix of big and tiny pore spaces. Once again, organic matter is crucial because it promotes the development of aggregate, crumbs, in the soil. Organic matter absorbs and stores water until it is needed by plant roots.
Each soil has a unique mix of these five fundamental components. By balancing them, you may significantly enhance the health of your soil and the productivity of your garden. But first, you must determine the type of soil you have.
Texture and Type of Soil
The texture of soil can vary from very fine particles to coarse and gravelly. You don't have to be a scientist to assess the texture of your garden's soil. Simply moisten some dirt in the palm of your hand and rub it between your fingers to get a rough idea.
Your soil is sandy if it feels gritty; silty if it feels smooth, like damp talcum powder; and clay if it feels coarse when dry, sticky or slippery when wet, or rubbery when damp.
Every soil has distinct physical properties that are determined by how it was made. The silty soil of an ancient floodplain differs from the rocky mountain soil; the clay soil that lay underneath a glacier for millions of years differs from the sandy soil near an ocean. Some of these fundamental traits can be strengthened with good management, while others can be harmed by misuse.
Soil types are typically classified based on the major kind of soil particles present: sand, silt, or clay. You can quickly determine the type of soil you're working with by doing a basic soil test.
You should do this test again with various soil samples from your lawn or garden.
1. Fill a quart jar roughly one-third full with topsoil and half-full with water.
2. Screw on the lid and briskly shake the liquid until all of the dirt clumps have dissolved.
3. Place the jar on a windowsill and see how the bigger particles settle to the bottom.
4. The sand part of the soil will settle to the bottom of the jar after a minute or two. Mark the sand level on the jar's side.
5. Leave the jar alone for several hours. The finer silt particles will settle onto the sand over time. The layers have slightly different colors, representing different kinds of particles.
6. Leave the jar alone overnight. The layer above the silt will be clay. Mark the thickness of that layer. A thin layer of organic matter will be on top of the clay. Some of the biological stuff may still be floating in the water.
The jar should be cloudy and full of floating organic material. If not, organic matter will be required to enhance the fertility and structure of the soil.
Enhancing Soil Structure
Even the most worsened soil can be enhanced, and your efforts will be rewarded back. Your plants will be more robust and productive if their roots are in good soil.
Sandy soil. Sand particles are large, irregularly formed pieces of rock. Huge air gaps between sand particles in sandy soil allow water to drain swiftly. Nutrients tend to wash away with the water frequently before plants can absorb them. As a result, sandy soils are typically deficient in nutrients.
Sandy soil also has a lot of air, which allows microorganisms to break down organic materials fast. Because sandy soils contain no clay or organic content, they lack a crumb structure. Even when the soil is damp, the particles do not stick together.
To enhance sandy soil, do the following:
- Work in 3 to 4 inches of organic matter such as well-rotted manure or finished compost.
- Mulch around your plants with leaves, wood chips, bark, hay, or straw. Mulch retains moisture and cools the soil.
- Add at least 2 inches of organic matter each year.
- Grow cover crops or green manures.
Clay Soil. Clay particles are tiny and flat in shape. They tend to pack together so densely that there is almost no pore space. When clay soils become moist, they become sticky and nearly unworkable. They drain slowly and can remain wet well into the spring. When they finally dry out, they usually become hard and cloddy, with the surface cracking into flat plates.
Clay soils are usually deficient in organic matter and microbial activity due to a lack of pore space. Plant roots are shorter because it is difficult for them to push through the dirt. Foot traffic and garden equipment can also contribute to compaction issues. Luckily, most clay soils are rich in minerals that will be available to your plants after the texture of the soil is improved.
To enhance clay soil, do the following:
- Work 2 to 3 inches of organic matter into the surface of the soil. Then add at least 1 inch more each year after that.
- Add the organic matter in the fall, if possible.
- Use permanent raised beds to improve drainage and keep foot traffic out of the growing area.
- Minimize tilling and spading.
Silty Soil. Silty soils include tiny irregularly shaped pieces of weathered rocks, making them very thick with limited pore spaces and poor drainage. They are often more fertile than sandy or clayey soils.
- To enhance silty soil, do the following:
- Add at least 1 inch of organic matter each year.
- Concentrate on the top few inches of soil to avoid surface crusting.
- Avoid soil compaction by avoiding unnecessary tilling and walking on garden beds.
- Consider constructing raised beds.
Soil pH
Your soil's pH level shows how acidic or alkaline it is. The pH of soil water is determined by the ratio of hydrogen (positive) ions to hydroxyl (negative) ions. The pH is neutral when the quantities of hydrogen and hydroxyl ions are equal (pH 7). Acidic soil occurs when hydrogen ions predominate (pH 1 to pH 6.5). When the hydroxyl ions tip the balance, the pH becomes alkaline (pH 6.8 to pH 14).
Most of the major plant nutrients are soluble at pH values ranging from 6.5 to 6.8, which is why most plants grow best in this range. If the pH of your soil is much higher or lower, soil nutrients get chemically bonded to soil particles, rendering them inaccessible to your plants. Plant health suffers as a result of the roots' inability to absorb the nutrients they require.
The pH of your soil should be between 6.5 and 6.8 to increase its fertility. You cannot and should not attempt to modify the pH of your soil in a single day. Instead, gradually change it over one or two growing seasons and then keep it up every year after that. It is also a good idea to apply organic matter liberally since it helps to regulate pH abnormalities.
Acidic Soil. If the pH of your soil is less than 6.5, it may be too acidic for most garden plants (although some, such as blueberries and azaleas require acidic soil).
The most recommended technique to raise the pH of your soil (making it less acidic) is to apply powdered limestone. Dolomitic limestone will also enrich the soil with manganese. Because it takes many months to change the pH, use it in the fall.
Wood ash will also raise the pH, and it works more quickly than limestone and contains potassium and trace elements. But if you add too much wood ash, you can drastically alter the pH and cause nutrient imbalances. For best results, apply wood ash in the winter, and apply no more than 2 pounds per 100 square feet, every two to three years.
To raise the pH of your soil by about one point:
- In sandy soil: add 3 to 4 pounds of ground limestone per 100 square feet.
- In loam (good garden soil): add 7 to 8 pounds per 100 square feet.
- In heavy clay: add 8 to 10 pounds per 100 square feet.
Alkaline Soil. If your soil pH is higher than 6.8, you need to acidify it. Typically, the soil is acidified by the addition of ground sulfur. Organic materials that are already acidic, such as pine needles, sawdust, peat moss, and oak leaves, can also be used.
To lower soil pH by about one point:
- In sandy soil: add 1 pound of ground sulfur per 100 square feet.
- In loam (good garden soil): add 1.5 to 2 pounds per 100 square feet.
- In heavy clay: add 2 pounds per 100 square feet.
Soil Testing
A professional soil test will provide a plethora of information about your soil, such as the pH and quantity of various nutrients.
A professional soil testing service may be available at your local Cooperative Extension Service office. The benefit is cheap cost and outcomes that are tailored to your unique region. If this service is not accessible, you can have your soil analyzed by a third-party soil lab. Choose one in your country's region if at all possible.
Soil test results usually rate the levels of soil pH, phosphorus, potassium, magnesium, calcium, and sometimes nitrogen. (Most labs do not test for nitrogen because it is so unstable in the soil.) Some labs also offer tests for micronutrients such as boron, zinc, and manganese. Unless you feel there may be a deficiency problem, you probably won't need micronutrient testing. As a preventative measure, you can apply organic fertilizers that include micronutrients (such as greensand and kelp meal).
Take a soil sample from each garden area, including the grass, flower garden, and vegetable garden, to ensure the most accurate test results. The best seasons to conduct a soil test are in the spring and fall. The soil is more stable and is the best time to apply any essential nutrients. Upon request, many laboratories will provide suggestions for particular organic changes. If not, you'll have to examine labels to find organic substitutes for any advised chemical fertilizers.
