Successful gardening requires good soil. All plants, flowers, vegetables, trees and shrubs, even the grass plants of your lawn need good soil in which to grow and thrive. Creating good soil is not difficult; and, it is always very rewarding.
Soil Components
Soil is a mix of mineral and organic matter, plus air and water. Mineral components come from weathered or dissolved rock matter; organic components come from decayed plant and animal materials. Air and water circulate within the spaces between the solid mineral and organic particles.
Minerals supply nutrients and give shape to the soil. Organic matter also supplies nutrients and effects how well plants are able to use the other three basic componentsminerals, water, and air.
Soil Textures
Soil’s texture is a function of the particle size of the minerals. There are three kinds of particles—sand (the largest), clay (the smallest), and silt, which has a particle size between sand and clay.
In sandy soil the shape of the individual sandy particles creates large spaces between them, so water and nutrients tend to run through sandy soils very quickly. Deserts and seashores are examples of sandy soils good for growing cacti and some specialty grasses, but not a good environment for most traditional garden plants.
Clay soil, at the other end of the texture spectrum, is comprised of very small solid particles that stick together and tend to have poor drainage and very little air between the particles. Wet clay soil sticks to everything, is very hard to cultivate, and is generally a somewhat hostile gardening environment.
Loamy soil consists of a good combination of sand, clay, and silt particles. The combination of particle sizes allows the loamy soil to hold water, air, and decaying organic matter. Loamy soil also supports good plant root development, and is the best environment for storing the nutrients and water that plant roots absorb as food.
Whatever kind of soil you have, you can make it better. You can always add what your soil lacks; but, it’s very difficult, if not impossible, to subtract what your soil has in excess. Soil improvement, then, is the process of adding what’s missing in order to create the proper balance.
Soil Structure Crumb and Tilth
Soil structure is determined by how well the soil particles stick together to form larger groups. The best structure is when soil particles combine to form small round shapes known as crumbs. Good crumb formation, like good texture, allows good root development and relatively free movement of air and water. A soil that is easy to cultivate is described as having good tilth. The key to good crumb formation and good tilth is having the right amount of organic matter in the soil. The best way to improve tilth in the soil is to till it in order to provide the optimum mixture of mineral particles and organic matter.
The Role of Organic Matter
There are two types of organic matter that are essential to good soil:
1. Dead plant and animal matter in various stages of decay, and
2. The living organisms from microscopic soil bacteria to earthworms that break down the organic matter.
When organic material decays, it becomes a dark, sticky material known as humus. The humus particles act like glue, holding individual soil particles together in larger groups. Humus doesn’t hold the particles as densely as clay, so water and air can still circulate through humus-rich soil. Humus also contributes to soil fertility.
Earthworms and soil bacteria continuously break down organic material to enrich the soil and help provide both good structure and texture. Earthworm tunneling creates pores for water and air to circulate, which in turn provides a healthy environment for soil microbes.
Soil Nutrients
The three major soil nutrients are: Nitrogen (N), Phosphorous (P), and Potassium (K). Indeed, most commercial fertilizers are labeled according to their N-P-K concentration.
Nitrogen affects good leaf and stem growth; it also causes the quick greening of newly fertilized lawns. Too much Nitrogen, however, can “burn” plants and actually kill them.
Phosphorous is important to root development and plays a key role in fruit ripening.
Potassium’s key role is that it enhances resistance to disease.
All other soil nutrients are called “minor elements” even though some are either very important or somewhat toxic to various plants. Copper (Cu), sulfur (S), and boron (B), for example, are very helpful for fruit trees; but, even small amounts of boron can be harmful to vegetable garden plants. Other micronutrients, sometimes called “trace elements,” include: Magnesium (Mg), Iron (Fe), Manganese (Mn), Zinc (Zn), and Calcium (Ca).
Soil Chemistry pH
The standard measure of soil acidity is pH. The pH scale ranges from 1 to 14, with 1 representing the most acid, 14 being the most alkaline (or basic), and 7 being neutral. Very rarely will soil have a pH outside of the range of 4-to-8. The soil’s pH is very important, as it affects how well the soil microbes perform as well as how well the plants roots absorb nutrients.
Areas with abundant rainfall typically have more acidic soils; and, all garden soils tend to become more acidic over time, as acids are created when organic matter decays. Thankfully, most garden plants tend to do perform very well in slightly acidic soils at about 6.5 on the pH scale, the point at which minerals are most soluble and therefore readily available to the plants as nutrients.
Rhododendrons, azaleas, and blueberries actually prefer acidic soil in the 4.5 to 5.0 range, and most serious azalea and blueberry gardeners use special fertilizer for “acid-loving plants.” In more alkaline, or basic, soils, their leaves turn yellow because iron intake is impeded.
Should You Get a Soil Test?
If your lawn or garden is performing poorly, you may want to check the soil’s pH. While there are a lot of home test kits available, most of the soil experts recommend a professional test. The home test kits are simply not very accurate, and obtaining a professional test is relatively easy and inexpensive. This is one instance where bad information may be worse than no information. If you’re going to amend your soil with anything other than good compost, make sure that you know what you have, and what you need!
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There are three main sources for soil tests:
Co-op or County extension services
University and Private soil labs
Most lawn care companies
You simply need to order a kit (consisting of a container, instructions, and a return shipping box/envelope), and send a sample of your soil to the lab. Most simple soil tests cost about $10 to $15. You can find a lab or lawn care service by searching online; try the American Horticultural Society, for example. Most tests will include both a pH reading and a nutrition analysis.
If a soil test or your plants’ performance indicates that your soil is too acidic, the best remedy is to apply pelletized lime to move the pH upward. Of course, the amount of lime will depend on both how acidic your soil is and your soil’s structure. When making adjustments to soil pH, it is better to do so gradually; it’s better to make adjustments over two or more years.
To raise the pH by 1 point (more alkaline), apply:
4 oz of lime per square yard in sandy soils
8 oz of lime per square yard in loamy soils
12 oz of lime per square yard in clay soils
25 oz of lime per square yard in peaty soils
To lower the pH by 1 point (more acidic), use ground rock sulfur, as follow:
1.2 oz of sulfur per square yard in sandy soils
3.6 oz of sulfur per square yard for other soils
Sawdust, composted leaves, wood chips, and peat moss will also lower the pH of soil. Peat moss is especially acidic, so use it sparingly, and only when you want to lower the pH of the soil in your garden.
Creating and Maintaining Better Soil
You can easily build and maintain better soil for both your lawn and your gardens. Better soil will have depth, tilth, and abundant nutrients for plant growth and health. Better soil enables both grass and garden plants to develop good root systems, which means they’ll thrive even when other conditions, like rainfall, aren’t ideal. And, better soil results in plants having the ability to resist or defend diseases.
Sandy Soil
If your soil is sandy, you can create better soil texture by adding top soil, dehydrated manure, or compost. If you have a source of fresh manure from a farm, compost the manure first before adding it to your soil. Fresh manure is simply too “hot” to add directly to your lawn or garden.
Compost is, by far, the single best soil additive because it contains both solid mineral particles (for texture and nutrition) as well as organic matter (for structure and nutrition). Compost also contains millions of microorganisms that that help keep soil “alive” by continuously breaking down mineral and organic matter into the proper form of nutrients for your plants.
Simply add several inches of compost to garden soil surfaces, and till it in to create a uniform mixture. Tilling will also help break up any larger clumps, speeding up the ongoing decomposition of organic matter.
Clay Soil
If your soil is mucky clay, you can improve its texture and structure by adding sand and compost. Sand will quickly improve the texture by separating some of the smaller mineral particles and allowing more openings for air and water circulation. Compost will improve the structure by providing humus, which builds more loosely compacted soil crumbs. And, compost will significantly boost your soil’s nutrient content and help plants resist disease.
Loamy Soil
If you are blessed with, or if you’ve created a healthy loamy soil, you still need to maintain it. Plants take nutrients from the soil, and traffic contributes to compaction which makes the soil denser. Even if you have good soil, you can probably improve it. The best way to maintain and improve soil is, of course, to add compost.
Add Compost
Compost is the single best additive for your soil because it contributes to texture, structure, nutrition, and helps regulate pH. “Hot,” or aerobic, composting occurs when a mix of “brown” materials and “green” materials quickly decomposes with the help of microorganisms, air, water, and sometimes worms. For more information on composting, click here.
Finely sifted compost can also be very beneficial to your lawn. The microbes will slow down thatch build-up, and the organic matter will help offset compaction from foot traffic. The Mantis ComposT-Twin has an optional sifter screen that makes sifting finished compost easy. Good soil—it’s essential to good gardening.
