Healthy Soil: The Foundation of a Thriving Garden
Soil is more than dirt - it’s a living, dynamic resource that sustains plant life by providing nutrients, water, air, and a home for countless organisms. Its texture, structure, and composition influence everything from drainage and nutrient storage to plant health and resilience. Understanding your soil type, pH, and structure helps you choose the right plants and amendments for optimal growth. With the right care - such as adding organic matter, improving drainage, and avoiding compaction - any soil can be enhanced to support a productive, beautiful garden.
What is it, exactly? Soil is a natural resource composed of organic matter, minerals, gases (air, for example), liquids, and organisms that together support life. It forms the upper layer of the Earth's crust, ranging from a few inches to one hundred feet deep depending on location, and is essential for plant growth. Different kinds of soil develop over thousands of years in different locations because soil retains some of the chemical and physical characteristics of the parent rocks from which it derives and is subject to different climatic conditions.
Here's a simple test you can do at home to make an educated guess where your garden soil falls within the four basic soil texture types: Pick up a small handful of moist soil and curl your fingers around it to form a roll. Using your thumb, push the roll end out across your forefinger to create a noodle-like flat ribbon as it exits.
- Clay, a fine textured soil. When moist soil is squeezed in the hand, a strong ribbon of clay can be formed that at times will reach more than two inches long when pressed through the fingers with the thumb.
- Clay loam, a medium textured soil containing clay and silt . A ribbon can be formed easily with moist soil that is moderately strong but will break away when one to two inches long.
- Loam, a medium-textured soil. A short ribbon can be formed with moist soil that will split readily and will break away when less that one inch long.
- Loamy sand, a coarse-textured soil. No ribbon can be formed, and the moist clump will break up easily.
Soil in good physical condition with good structure and tilth (the suitability for growing plants) can hold and provide plant roots with adequate quantities of nutrients, water, and air; it will drain well and be easy to work without becoming sticky when wet or crusted when dry.
Soil texture affects many properties that influence plant growth. The coarser the soil texture, the faster the soil warms up in the spring for earlier planting, and the faster it will drain. Water holding and nutrient storage capacities are determined mostly by the distribution of particle sizes in the soil. Those with finer textures (higher percentages of silt and clay) hold more water and nutrients than coarser-textured soil (higher percentages of sand.) Conversely, heavy clay soil can absorb and adhere the water so completely that it is withheld from plants. Loam, sandy loam and silt loam containing about 5-10 percent organic matter are said to be the best soils for home garden cultivation because they provide a mixture of sand, silt, and clay, which retain sufficient water but also permit infiltration and percolation.
Physical soil amendments can enhance the tilth and manageability of small beds and garden areas where ornamental plants and vegetable crops are regularly removed and replanted. Occasional additions of organic matter (such as plant residues, compost or manures) in these planting areas ensure a continuous supply of energy for soil microorganisms. As the soil microbes decompose the organic matter, they convert it into inorganic nutrients that can be used by growing plants. They also help to maintain good soil structure through the release of compounds into the soil environment that cement small soil particles together.
It is useful to know the composition of your soil and the pH (acidity or alkalinity) because both affect the nutrient uptake. Our Western US soils are generally more alkaline, and most plants prefer soils that are neither very acid nor very alkaline. Both composition and pH can be confirmed by a soil test. While testing is best conducted by a laboratory, home kits are available at farm stores, garden centers, or online. Digital meters that measure soil moisture and approximate pH are available at a nominal cost at big box stores.
It is possible to amend the soil pH with the addition of organic materials and specific minerals like sulfur or lime in the correct proportions, but changes to pH are temporary and slow to achieve. It is simpler to select plants that will thrive in or adapt to the available soil type. Planting in a pot with the desired soil is another easy solution.
Virtually all soils can be improved before planting by the addition of organic materials like garden compost to add nutrients and improve texture, especially clayey or sandy soils when amended by 30% of volume. This amounts to adding 10-20 cubic feet of amendments per 100 square feet of soil. Adding rotted leaves or leaf mold, composted sawdust from untreated wood or lawn clippings not treated recently with pesticides, or bagged soil amendments will enrich and loosen soil texture and improve water filtration. Organics may be used as a mulch on top or preferably mixed into the soil. With time and decomposition all of these will add to the soil’s fertility, and when fully decomposed (nutrient depleted), should be replenished every one to two years. Fertilizers also add nutrients, and mycorrhizal additives containing useful bacteria and fungi increase microbial activity to break down organic materials into available nutrients. Follow the package instructions for fertilizers and mycorrhizal additives.
To improve the soil for container grown plants, add compost for extra nutrients and grit like small gravel or pumice, vermiculite, or perlite to increase drainage and air flow.
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Home garden composting creates a nutrient-rich soil amendment and recycles materials that otherwise need to be discarded, but bagged compost can be purchased along with chemical fertilizers and organic fertilizers like bone meal, seaweed and fish extracts, worm castings, or composted animal manures (used in moderation to avoid chemical salt buildup.) Always follow the package instructions for fertilizers and lean toward using a bit less or a weaker, diluted solution rather than too much or too often.
To maintain the best soil structure, avoid over-tilling it, working it when it is wet, or compacting it in growing areas by walking on it. Rotate plants to avoid a build-up of bacteria in the soil and mulch plants (avoiding the central stem area) to stop soil splash-up during watering that can spread diseases and help retain water. To avoid future infections, remove diseased leaf litter from the soil around plants and do not add these to the compost pile.
When the soil is overwatered, all or most of the pore spaces fill with water. Because oxygen is not readily available in waterlogged soil, plant roots cannot respire efficiently; they become oxygen starved and cannot make efficient use of available nutrients. The plant roots can suffocate, and seeds sown in overly wet soil may not germinate due to lack of oxygen.
Drought significantly impacts soil health by reducing moisture levels, altering nutrient availability, and increasing erosion risks, which can lead to long-term degradation of soil quality. It is always best to water less frequently and more deeply to encourage roots to reach deep into the soil for better health.
Soil Testing
Soil Test Companies
Call to see how they want sample to be prepared.
- Orange County Farm Supply in Orange (714) 978-6500.
- Waypoint Analytical, Inc., Anaheim (714-282-8777)
- Wallace Laboratories, El Segundo (800-473-3699)
Soil Test Kits
- La Motte Soil Test Kit (La Motte Co., Chesteron, MD)
- Rapidtest® (Luster Leaf Products, Woodstock, IL)
- Mysoil Soil Test Kit https://www.mysoiltesting.com (Walla Walla, WA)