Soil amendments needed to make it more productive

Soils ideal for growing ornamental plants and vegetables are rare, especially in Nevada. Since ancient times, farmers all over the world have worked organic materials into the soil to make it more productive.

Each year we plant in a soil, it needs to be replenished. Many different materials, such as bark, sawdust, manure, sludge, compost, rice hulls and inorganic conditioners, are available to improve a soil's physical condition. Rebuilding a soil increases water retention and allows for better movement of air and water by physically separating the soil particles. It also sustains the microorganisms that make a soil a vital growing medium for plants.

Soil amendments are worked into the soil to make it more productive. Actually, fertilizer is also an amendment, but the term "amendment" more commonly refers to added materials other than fertilizer.

Sandy soils benefit from humus-type amendments that increase water- and nutrient-holding capacity. Loose, fibrous types of materials increase permeability in clayey soils.

Since soil is the building block for plant growth, if a budget is tight, it is much wiser to spend more money on building the soil and less money on purchasing plants. Heed the old adage, "Don't plan a $5 plant in a 50-cent hole."

The best time to amend soil is before planting, because it is difficult to work amendments into the soil after plants are established. For turf and ground covers, the "Western Fertilizer Handbook" suggests using about 33 percent by volume of amendment. This means that to improve a soil to a 7-inch depth, approximately 7cubic yards of amendment per 1,000 square feet should be added. To improve a soil to a 9-inch depth, work in about 9 cubic yards per 1,000 square feet. Vegetable gardens benefit from 2 inches of amendment incorporated into the soil to a 6-inch depth. Provide your plants with a uniform soil mixture throughout the entire root area by double-digging or rototilling. Grade the area after mixing in the amendments to remove low spots and direct drainage.

Amendments decompose over time. Grass clippings, manures and mushroom compost may break down in days to weeks. Leaf mold and composts last up to six months or more. Rice hulls, redwood and barks may last years.

Whatever amendment you choose, make sure to amend your soil each year. For information on soil amendments and gardening, contact me, (775) 887-2252 or, or your local University of Nevada Cooperative Extension office. Check out useful horticulture publications at "Ask a Master Gardener" at

n JoAnne Skelly is the Carson City/Storey County Extension educator for University of Nevada Cooperative Extension.


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