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?
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.
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.
Composting for the