Bed PreParation: insurance for success 37
decomposition that it does little to improve the structure of the soil. You want
the bales of sphagnum peat, not the bags of muck peat.
compoSted bioSolidS This is the fancy “cocktail party” name for com-
posted municipal sewage sludge. Composted biosolids can improve the physical
structure of soil by increasing drainage, aeration, and moisture retention. They
also recharge soil with microbial life. Sewage sludge is composted with different
bulking agents, so again there will be differences in products from different
sources. The one I use is composted with hardwood chips; others might be
bulked with sawdust or other bulking materials. The pH is slightly above neutral,
averaging pH 7.3–7.6, and the organic content is 56–72 percent. It contains a
well-balanced macro- and micro-nutrient content (1.0–1.5 percent N, 0.4–2.0
percent P, 0.2–0.4 percent K) in organic forms, so the nutrients are released
slowly over time and thus with no concern for burn, assuming the material has
been applied at the recommended rates. Within the 1st year after application
approximately 25 percent of the nitrogen is released, 10 percent in the 2nd and
3rd years, and 5 percent in the 4th and 5th years. During the 1st year approxi-
mately 30 percent of the phosphorous and 70 percent of the potassium are
available. Because compost is high in phosphorus, supplemental phosphorus
fertilizer might not be needed at bed preparation, depending on the quantity of
composted biosolids used and the quantity of phosphorous present in the native
soil. Composted biosolids are high in phosphorus and also supply good levels of
calcium, magnesium, zinc, iron, and copper. Research has shown a 29 percent
increase in dry weight of perennials when grown in soils amended with com-
posted biosolids. Composted biosolids have also been shown to help suppress
disease in turf. We as gardeners, landscape and horticulture professionals, and
general stewards of the land have a commitment to our environment to utilize
these alternatives for waste recycling.
Because of the varying composition of composts from different sources, I
want to reemphasize the importance of requesting tests for nutrient content, pH
level, and levels of soluble salts. Heavy metals, fecal pathogens, and parasites
must be strictly controlled at all composting locations; detailed studies have
shown that these factors do not pose a concern under existing regulations. Your
supplier can provide you with information on these as well as on nutrient
content, percentage of organic matter, and recommended application rates.
Again, follow these recommended rates, because overapplication of compost can
lead to many other problems.
muShroom compoSt A byproduct from mushroom production is another
good amendment for improving soil properties. One available to me is a combi-
nation of steam-sterilized horse manure, sphagnum peat moss, brewer’s grain,
lime, and gypsum. It contains about 60 percent organic matter and has a pH of
7.8–8.2. High in nutrients, mushroom compost has a N–P–K content of 1.5–0.75–
1.5, and it also supplies calcium. This is just one recipe, and not a common one at
that. As always, request an analysis of the available product, including soluble
salts, which can be high, and information about how it is processed. Not all
products are the same.
b ark compoStS Low in the nutrients they provide, bark composts are often
used to improve the structure of soils. Bark compost material composed of large,
coarse particles up to 2 1/2 in. in size will help loosen heavy clay soils. Finer
particles help bind sandy soils. Make sure it is composted, or you will need to add
supplemental nitrogen. Studies have shown that hardwood bark compost can
naturally suppress root rots, Fusarium wilts, and some nematode infections. The
soil must be well draining in order for disease suppression to be effective.
compoSted manure A valuable source of major nutrients, trace elements,
and large populations of bacteria—bacteria that can help convert organic