Gardening : Survey Finds Ingredients in Soil Are a Mixed Bag
Buying a bag of soil is not unlike gambling in Atlantic City. It’s impossible to know just what is going to turn up.
A recent marketing survey involving the Farm Resource Center in Putnam, Conn., indicates that labels on bagged soil can be misleading, Organic Gardening magazine reported.
A bag labeled “cow manure” had no cow manure in it but did contain chicken manure, which can burn the roots of seedlings, reported Lucien LaLiberty Jr., Farm Resource Center president.
“A bag labeled ‘top soil’ had, at best, very little soil of any kind,” he said. “It appeared to be mostly black peat. Some of the material in the bags contained contaminants, including heavy metals.”
Proportions Unknown
Packages labeled “potting soil” or “seed starting mix” usually list the ingredients but not the proportions. The word compost , when used to describe an ingredient, is imprecise, because there is no indication of what it contains or how it was made.
Even the word peat is misleading, LaLiberty said, because there are several different kinds of peat.
“The basic problem,” he said, “is that there are no state or federal standards to regulate the manufacturing process of these materials. And there is no trade association that could come up with industry-wide standards.”
LaLiberty said he expects that standards for these products will be set within the next several years, as the industry matures and becomes better organized.
A Recipe for Soil
Organic Gardening has published a formula for mixing your own soil, devised by Elliott Coleman, manager at the Mountain School in Vershire, Vt.:
20 quarts black peat
20 quarts brown peat
10 quarts well-made compost
10 quarts soil
6 quarts coarse sand
1/2 cup dolomitic lime
1 cup colloidal phosphate
1 cup greensand
1 cup blood meal
First, mix the lime thoroughly with black peat, because the latter is the most acidic component.
Then add the soil and compost.
Add the coarse sand and mix in. Then add the brown peat, followed by the phosphate, greensand and blood meal.
Coleman said he uses soil in his mix because it reduces the need for compost, which he believes might make the mix too rich. He recommends garden soil.
“I think one of the best preceding crops for any soil are onions. So get the soil for the mix from wherever onions have been growing. I find it works marginally better.”
Coleman suggests that substituting 75% peat and 25% compost for the first four ingredients will serve “pretty well, though you won’t do as well with brassicas (such as cauliflower, broccoli and cabbage) that way.”
The mix, he cautioned, should be prepared three months in advance of use.
