Garden Soil Amendments

Improving garden soils with soil amendments

By: Sandy Feather 2010
Penn State Extension

Q. I am starting a new vegetable garden, and I was wondering what the best soil amendment would be. I have access to free horse manure, but someone told me I would get a lot of weeds from it. Would peat moss or mushroom compost be better?

A. It's true that many weed seeds pass through an animal's digestive system intact and ready to sprout when environmental conditions permit, so you can wind up with a lot of weeds from horse manure. However, it can be a good soil amendment that increases the organic content as well as the fertility of your soil. Because you have ready access to horse manure, you can till it into your garden, allow the weeds to sprout, and then till them under or kill them with a nonselective herbicide such as herbicidal vinegar (20 percent, not the 5 percent vinegar found in your kitchen), a soap-based herbicide such as Sharpshooter or Roundup (glyphosate) before planting your vegetables.

Horses bring us horse manure and the basics for mushroom compost

To minimize weed problems, you might want repeat this process by tilling the garden again to bring more weed seeds up to the soil surface to germinate, then till them under or kill them. Then you should put down a 2 to 3 inch layer of mulch, and disturb the soil as little as possible when you plant to minimize weeds. In light of food safety concerns, the USDA now recommends against using fresh manure within 120 days of harvest.


Peat moss is OK as a soil amendment, but it is nutrient-poor and tends to acidify the soil slightly. If your soil needs to be acidified, peat moss would be fine. You should have your soil tested so that you know what is needed to get the pH (acidity or alkalinity) into the optimum range of 6.2 to 6.8 that most vegetable crops prefer, as well as what specific nutrients are required.

Mushroom compost is a great soil amendment, but it has a high pH and also has a high soluble salt content. If your soils are too acidic and the pH needs to be raised for optimum vegetable growth, mushroom compost might be the best choice for your garden.


Soil amendments

Saving Vegetable Seed

Composting for the garden


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