with slag, Rodale advises the user to be alert to the fact that some
contain little in the way of useful nutrients and/or may contain
excessive amounts of sulfur. Large quantities of sulfur can acidify
soil. Read the analysis on the label. Agriculturally useful slag has
an average composition of 40 percent calcium and 5 percent
magnesium. It must also be very finely ground to be effective. See
also: _Lime_ and _Rock dust._

_Beet wastes,_ like bagasse, are a residue of extracting sugar. They
have commercial value as livestock feed and are sold as dry pulp in
feed stores located near regions where sugar beets are grown. Their
C/N is in the vicinity of 20:1 and they may contain high levels of
potassium, reaching as much as 4 percent.

_Brewery wastes._ Both spent hops (dried flowers and leaves) and
malt (sprouted barley and often other grains) are potent nutrient
sources with low C/N ratios. Spent malt is especially potent because
brewers extract all the starches and convert them to sugar, but
consider the proteins as waste because proteins in the brew make it
cloudy and opaque. Hops may be easier to get. Malt has uses as
animal feed and may be contracted for by some local feedlot or
farmer. These materials will be wet, heavy and frutily odoriferous
(though not unpleasantly so) and you will want to incorporate them
into your compost pile immediately.

_Buckwheat hulls._ Buckwheat is a grain grown in the northeastern
United States and Canada. Adapted to poor, droughty soils, the crop
is often grown as a green manure. The seeds are enclosed in a
thin-walled, brown to black fibrous hulls that are removed at a
groat mill. Buckwheat hulls are light, springy, and airy. They'll