While preparing this book, I queried the venerable Dr. Herbert H.
Koepf about lime in the compost heap. Koepf's biodynamic books
served as my own introduction to gardening in the early 1970s. He is
still active though in his late seventies. Koepf believes that lime
is not necessary when composting mixtures that contain significant
amounts of manure because the decomposition of proteinaceous
materials develops a more or less neutral pH. However, when
composting mixtures of vegetation without manure, the conditions
tend to become very acid and bacterial fermentation is inhibited. To
correct low pH, Koepf recommends agricultural lime at 25 pounds per
ton of vegetation, the weight figured on a dry matter basis. To
guestimate dry weight, remember that green vegetation is 70-80
percent water, to prevent organic material like hay from spoiling it
is first dried down to below 15 percent moisture.

There is another reason to make sure that a compost pile contains an
abundance of calcium. Azobacteria, that can fix nitrate nitrogen in
mellowing compost piles, depend for their activity on the
availability of calcium. Adding agricultural lime in such a
situation may be very useful, greatly speed the decomposition
process, and improve the quality of the compost. Albert Howard used
small amounts of lime in his compost piles specifically to aid
nitrogen fixation. He also incorporated significant quantities of
fresh bovine manure at the same time.

However, adding lime to heating manure piles results in the loss of
large quantities of ammonia gas. Perhaps this is the reason some
people are opposed to using lime in any composting process. Keep in
mind that a manure pile is not a compost pile. Although both will
heat up and decay, the starting C/N of a barnyard manure pile runs