Chicken manure compost is another matter.  Mix the pure manure with straw, sawdust, or other bedding, compost it and, depending on the amount and quantity of bedding used and the time allowed for decomposition to occur, the resultant C/N will be around 12:1 or above.  Any ripened compost around 12:1 still will GROW plants beautifully.  Performance drops off as the C/N increases.

Since chicken manure was scarce, most pre-twentieth century market gardeners depended on seemingly unlimited supplies of “short manure,” generally from horses.  The difference between the “long” and the “short” manure was bedding.  Long manure contained straw from the stall while short manure was pure street sweepings without adulterants.  Hopefully, the straw portion of long manure had absorbed a quantity of urine.

People of that era knew the fine points of hay quality as well as people today know their gasoline.  Horses expected to do a day’s work were fed on grass or grass/clover mixes that had been cut and dried while they still had a high protein content.  Leafy hay was highly prized while hay that upon close inspection revealed lots of stems and seed heads would be rejected by a smart buyer.  The working horse’s diet was supplemented with a daily ration of grain.  Consequently, uncomposted fresh short manure probably started out with a C/N around 15:1.  However, don’t count on anything that good from horses these days.  Most horses aren’t worked daily so their fodder is often poor.  Judging from the stemmy, cut-too-late grass hay our local horses have to try to survive on, if I could find bedding-free horse manure it would probably have a C/N more like 20:1.  Manure from physically fit thoroughbred race horses is probably excellent.

Using fresh horse manure in soil gave many vegetables a harsh flavor so it was first composted by mixing in some soil (a good idea because otherwise a great deal of ammonia would escape the heap).  Market gardeners raising highly demanding crops like cauliflower and celery amended composted short manure by the inches-thick layer.  Lesser nutrient-demanding crops like snap beans, lettuce, and roots followed these intensively fertilized vegetables without further compost.

Long manures containing lots of straw were considered useful only for field crops or root vegetables.  Wise farmers conserved the nitrogen and promptly composted long manures.  After heating and turning the resulting C/N would probably be in a little below 20:1.  After tilling it in, a short period of time was allowed while the soil digested this compost before sowing seeds.  Lazy farmers spread raw manure load by load as it came from the barn and tilled it in once the entire field was covered.  This easy method allows much nitrogen to escape as ammonia while the manure dries in the sun.  Commercial vegetable growers had little use for long manure.

One point of this brief history lesson is GIGO:  garbage in, garbage out.  The finished compost tends to have a C/N that is related to the ingredients that built the heap.  Growers of vegetables will wisely take note.