Anyone interested in learning more about preindustrial market gardening might ask their librarian to seek out a book called French Gardening by Thomas Smith, published in London about 1905.  This fascinating little book was written to encourage British market gardeners to imitate the Parisian marcier, who skillfully earned top returns growing out-of-season produce on intensive, double-dug raised beds, often under glass hot or cold frames.  Our trendy American Biodynamic French Intensive gurus obtained their inspiration from England through this tradition.

Curing the Heap

The easiest and most sure-fire improver of compost quality is time.  Making a heap with predominantly low C/N materials inevitably results in potent compost if nitrate loss is kept to a minimum.  But the C/N of almost any compost heap, even one starting with a high C/N will eventually lower itself.  The key word here is eventually. The most dramatic decomposition occurs during the first few turns when the heap is hot.  Many people, including writers of garden books, mistakenly think that the composting ends when the pile cools and the material no longer resembles what made up the heap.  This is not true.  As long as a compost heap is kept moist and is turned occasionally, it will continue to decompose.  “Curing” or “ripening” are terms used to describe what occurs once heating is over.

A different ecology of microorganisms predominates while a heap is ripening.  If the heap contains 5 to 10 percent soil, is kept moist, is turned occasionally so it stays aerobic, and has a complete mineral balance, considerable bacterial nitrogen fixation may occur.

Most gardeners are familiar with the microbes that nodulate the roots of legumes.  Called rhizobia, these bacteria are capable of fixing large quantities of nitrate nitrogen in a short amount of time.  Rhizobia tend to be inactive during hot weather because the soil itself is supplying nitrates from the breakdown of organic matter.  Summer legume crops, like cowpeas and snap beans, tend to be net consumers of nitrates, not makers of more nitrates than they can use.  Consider this when you read in carelessly researched garden books and articles about the advantages of interplanting legumes with other crops because they supposedly generate nitrates that “help” their companions.

But during spring or fall when lowered soil temperatures retard decomposition, rhizobia can manufacture from 80 to 200 pounds of nitrates per acre.  Peas, clovers, alfalfa, vetches, and fava beans can all make significant contributions of nitrate nitrogen and smart farmers prefer to grow their nitrogen by green manuring legumes.  Wise farmers also know that this nitrate, though produced in root nodules, is used by legumes to grow leaf and stem.  So the entire legume must be tilled in if any net nitrogen gain is to be realized.  This wise practice simultaneously increases organic matter.