One of the most environmentally-friendly soil amendments can be mushroom compost, which can supply nutrients and increase the water-holding capacity of the soil.
Use compost for "green" results in your growing area

October 02, 2008

By Edna LaFour, Victoria County Master Gardener

Edited by Charla Borchers Leon, Victoria County Master Garden
How well your plants grow and develop depends largely on the fertility of the soil that they are planted in. Determining the fertility is important, and soil sampling the growing area is essential to determine existing nutrients as well as those that are lacking. Soil amendments should be added only when a need is determined and only in the proper amount.


If used at the proper rate, one of the most environmentally friendly soil amendments can be mushroom compost, which can supply nutrients and increase the water-holding capacity of the soil. It contains nitrogen to promote growth, phosphorous for root growth and potassium (potash) to improve flowering and fruiting and has many more nutrients.

Mushroom compost does not have a high nitrogen level, therefore is safer to use than commercial fertilizers, but still it is too high to use solely as the only planting media. Let it be part of your total mix. But, do be careful and investigate the phosphorus levels of your soil before and after adding mushroom compost. It is typically part chicken manure and cottonseed meal, both of which have high phosphorus levels and can lead to problems if over applied or applied too frequently. It may even be a wise choice to consider ordering mushroom compost in the fall and letting it “cure” in a pile over the winter before using it.


Each mushroom growing facility has its own recipe for growing mushrooms. The closest grower/supplier in our area uses wheat straw, cottonseed meal, poultry litter, gypsum cottonseed burrs nitrogen balanced with urea, vegetable oil, brewers grain, peat moss and sugar beet lime. A soil test of the mushroom compost can provide the nutrient levels and the results may be available from the entity selling the compost. When necessary, a pyrethrin insecticide may also be added to the compost.


Weeds can be a major problem in most composted materials but you don’t have to worry about contaminating your flower bed, yard or vegetable gardens with weeds when you use mushroom compost. Mushroom growers take every precaution to make sure there are no foreign weeds or bacteria in the growing media and they pasteurize the mushroom compost before it is placed into the growing trays to produce your edible mushrooms.


According to Carol Savonen, Oregon State University Extension Service, mushroom compost is very rich, and according to Kitchen Pride Mushroom Farm in Gonzales, it is best to not plant directly into it. However, when used correctly it is a wise selection to enrich your soil.

The soluble salts and other nutrients in fresh, undiluted mushroom compost are too concentrated for germinating seeds, using on young plants and on other salt sensitive plants, especially those in the heath family such as azaleas, blueberries and camellias. But, it is considered non-burning when you mix it into the soil or top dress established existing plants.

Before planting your flower beds or vegetable gardens, apply a 2- to 3-inch layer of mushroom compost on top of your beds and till it in several inches deep. Mushroom compost can also be used as mulch around perennials, trees and shrubs.

When using mushroom compost for container plants, mix one part mushroom compost to three or four parts garden soil or sand. Be sure to have adequate drainage in your container, and water thoroughly after applying or planting.


Seeding new lawn

Late summer or early fall is the best time to seed new lawns and the best time to incorporate mushroom compost into your seeding plan. Prepare the seed area with 1-2 inches of mushroom compost and till into the soil to a depth of 4-6 inches for maximum benefit. Sow the seed uniformly over the soil surface at a recommended rate for your seed. Cover the grass seed with another - to -inch layer of mushroom compost and rake the area lightly to ensure good soil-seed contact. Then water well.

Laying sod

When laying sod on a new lawn prepare the lawn the same as for a seeded lawn. Moisten the soil well and lay the sod. After laying the sod, uniformly apply inch of mushroom compost on the seams for improved rooting.

Renewing established lawn

To renew an older, established lawn, aerate the lawn, preferably with a core aerator, and uniformly spread about -inch layer of mushroom compost over the lawn’s surface. Rake with a flexible rake to work it into cored holes and the lawn and water thoroughly.


While large acreage use of mushroom compost is certainly beneficial, the economics of it needs to be evaluated by the producer. We are fortunate to have Kitchen Pride Mushroom Farm of Gonzales nearby ( to supply our area, as they are also the only mushroom grower in our area. Mushroom compost is also available from the local garden centers in 40 or 50 pound bags.

When buying or ordering mushroom compost, remember that one cubic yard of compost will cover about 160 square feet to a depth of about 2 inches.

With judicious and proper use, mushroom compost can be an enriching soil amendment that will bring back life to your soil and provide you with optimum potential for fabulous foliage, flowers and fruit.

The Gardeners’ Dirt is edited by Charla Borchers Leon and is written by members of the Victoria County Master Gardener Association, an educational outreach of Texas Cooperative Extension-Victoria County. Mail your questions in care of the Advocate, P.O. Box 1518, Victoria, TX 77901; or, or comment on this column at
Mushroom compost advantages
*Excellent organic matter
*Balanced nutrients
*Slow release of nutrients
*Great soil builder/improver
*Very fine material, easy to spread or till in

Mushroom compost disadvantages

*Possible low nutrient level compared to other composts
*Possible buildup of phosphorus and salts with continued use
*Minimal microbial action initially due to pasteurization

When using mushroom composte for container plants, mix one part mushroom compost to three or four parts garden soil or sand.