Soil & Compost 101

Soil is more than just "dirt." Healthy soil forms the basis for a healthy garden. Get started on improving your soil as soon as possible. For example, if you plan to begin planting in the spring, start building healthy soil during the fall season. Before you begin gardening, it is important to determine what type of soil you have. Then, you can select plants that are best suited to your soil type. Read below to learn about soil types and ways to improve soil quality.

Soil Texture

​ Clay soil is moist and fertile, with good water retention. However, it is slow to warm in spring, yielding a shorter growing season. Clay can be improved by adding compost to decrease compaction and fine gravel or coarse sand to allow for proper drainage.

Sandy soil is easy to manipulate and drains quickly, It is quick to warm in spring, allowing for a longer growing season. However, sand dries out easily with low precipitation, loses nutrients due to quick drainage, and it is prone to high acidity. Improve sandy soil by mulching to increase moisture retention, planting cover crops to add organic matter, and testing pH regularly.

Loamy soil​ holds moisture and nutrients well, so plants need minimal water and fertilization. Thus, loamy soil supports a wide range of plants. However, over-fertilization is possible due to nutrient-rich soil. Regular testing and maintenance of soil pH is still important with loamy soil.

pH Level

The pH scale runs from 1.0 (acidic) to 14.0 (alkaline). Most plants prefer a neutral pH (close to 7.0). Soil samples can be sent to a laboratory for testing (contact your local university extension office), or you can use a take-home test kit.

Alkaline soil (pH > 7) typically has good drainage and warms quickly in spring. To lower soil pH (make more acidic), add pine needles, shredded leaves, sulfur, sawdust, or peat moss.

Acidic soil (pH < 7) supports some plants, such as eggplants, potatoes, and tomatoes. However, most fruits and vegetables require moderate acidity levels. To raise soil pH (make more alkaline), add ground limestone or wood ash.

Soil Improvement Techniques

Amend and improve the soil each season. Also avoiding walking on soil or working it with tools when wet to minimize compaction. Use paths or stepping stones to avoid compacting soil during weeding or maintenance.

Mulching regulates the soil temperature, controls weeds, and increases moisture retention. Inorganic mulches (i.e. newspaper, felt paper, plastic) can be spread throughout the year. Organic mulches (i.e. bark, coffee grounds, grass clippings, dried leaves, pine needles, saw dust) should be added in late fall or winter. Spread mulch across the surface of the soil to a thickness of 2-4 inches.

Composting boosts soil fertility and plant productivity. It is a natural form of recycling that reduces solid waste and decreases the need for chemical fertilizers. Compost is simply decomposed organic matter produced from kitchen scraps, lawn clippings, etc. It is worked into soil rather than laid on top.

Cover cropping increases organic matter, reduces erosion and compaction, increases nutrient levels, suppresses weeds, and attracts beneficial insects. Examples of cover crops include buckwheat, oats, clover, and alfalfa. As a source of organic matter, cover crops can be tilled into soil just before they begin to flower. Alternatively, cover crops can be cut at ground level and laid on top of soil as mulch.


Cornell University Cooperative Extension: Soil Basics
Rebel Tomato: Soil Health