Lime. There is no disputing that calcium is a vital soil nutrient as essential to the formation of plant and animal proteins as nitrogen. Soils deficient in calcium can be inexpensively improved by adding agricultural lime which is relatively pure calcium carbonate (CaC03). The use of agricultural lime or dolomitic lime in compost piles is somewhat controversial. Even the most authoritative of authorities disagree. There is no disputing that the calcium content of plant material and animal manure resulting from that plant material is very dependent on the amount of calcium available in the soil. Chapter Eight contains quite a thorough discussion of this very phenomena. If a compost pile is made from a variety of materials grown on soils that contained adequate calcium, then adding additional lime should be unnecessary. However, if the materials being composted are themselves deficient in calcium then the organisms of decomposition may not develop fully.
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 around 10:1 while a compost heap of yard waste and kitchen garbage runs 25:1 to 30:1. Any time highly nitrogenous material, such as fresh manures or spring grass clippings, are permitted to decompose without adjustment of the carbon-to-nitrogen ratio with less potent stuff, ammonia tends to be released, lime or not.
Only agricultural lime or slightly better, dolomitic lime, are useful in compost piles. Quicklime or slaked lime are made from heated limestone and undergo a violent chemical reaction when mixed with water. They may be fine for making cement, but not for most agricultural purposes.
Linseed meal. See Cottonseed meal.
Manure. Fresh manure can be the single most useful addition to the compost pile. What makes it special is the presence of large quantities of active digestive enzymes. These enzymes seem to contribute to more rapid heating and result in a finer-textured, more completely decomposed compost that provokes a greater growth response in plants. Manure from cattle and other multi-stomached ruminants also contains cellulose-decomposing bacteria. Soil animals supply similar digestive enzymes as they work over the litter on the forest floor but before insects and other tiny animals can eat much of a compost heap, well-made piles will heat up, driving out or killing everything except microorganisms and fungi.
All of the above might be of interest to the country dweller or serious backyard food grower but probably sounds highly impractical to most of this book's readers. Don't despair if fresh manure is not available or if using it is unappealing. Compost made with fresh, unheated manure works only a little faster and produces just a slightly better product than compost activated with seed meals, slaughterhouse concentrates, ground alfalfa, grass clippings, kitchen garbage, or even dried, sacked manures. Compost made without any manure still "makes!"
When evaluating manure keep in mind the many pitfalls. Fresh manure is very valuable, but if you obtain some that has been has been heaped up and permitted to heat up, much of its nitrogen may already have dissipated as ammonia while the valuable digestive enzymes will have been destroyed by the high temperatures at the heap's core. A similar degradation happens to digestive enzymes when manure is dried and sacked. Usually, dried manure comes from feedlots where it has also first been stacked wet and gone through a violent heating process. So if I were going to use sacked dried manure to lower the C/N of a compost pile, I'd evaluate it strictly on its cost per pound of actual nitrogen. In some cases, seed meals might be cheaper and better able to drop the heap's carbon-to-nitrogen ratio even more than manure.
There are many kinds of manure and various samples of the same type of manure may not be equal. This demonstrates the principle of what goes in comes out. Plants concentrate proteins and mineral nutrients in their seed so animals fed on seed (like chickens) excrete manure nearly as high in minerals and with a C/N like seed meals (around 8:1). Alfalfa hay is a legume with a C/N around 12:1. Rabbits fed almost exclusively on alfalfa pellets make a rich manure with a similar C/N. Spring grass and high quality hay and other leafy greens have a C/N nearly as good as alfalfa. Livestock fed the best hay supplemented with grain and silage make fairly rich manure. Pity the unfortunate livestock trying to survive as "strawburners" eating overly mature grass hay from depleted fields. Their manure will be as poor as the food and soil they are trying to live on.