Before the twentieth century, the fertilizers market gardeners used
were potent manures and composts. The vegetable gardens of country
folk also received the best manures and composts available while the
field crops got the rest. So I've learned a great deal from old
farming and market gardening literature about using animal manures.
In previous centuries, farmers classified manures by type and
purity. There was "long" and "short" manure, and then, there was the
supreme plant growth stimulant, chicken manure.
Chicken manure was always highly prized but usually in short supply
because preindustrial fowl weren't caged in factories or permanently
locked in hen houses and fed scientifically formulated mixes. The
chicken breed of that era was usually some type of bantam,
half-wild, broody, protective of chicks, and capable of foraging. A
typical pre-1900 small-scale chicken management system was to allow
the flock free access to hunt their own meals in the barnyard and
orchard, luring them into the coop at dusk with a bit of grain where
they were protected from predators while sleeping helplessly. Some
manure was collected from the hen house but most of it was dropped
where it could not be gathered. The daily egg hunt was worth it
because, before the era of pesticides, having chickens range through
the orchard greatly reduced problems with insects in fruit.
The high potency of chicken manure derives from the chickens' low
C/N diet: worms, insects, tender shoots of new grass, and other
proteinaceous young greens and seeds. Twentieth-century chickens
"living" in egg and meat factories must still be fed low C/N foods,
primarily grains, and their manure is still potent. But anyone who
has savored real free-range eggs with deep orange yokes from
chickens on a proper diet cannot be happy with what passes for
"eggs" these days.
Fertilizing with pure chicken manure is not very different than
using ground cereal grains or seed meals. It is so concentrated that
it might burn plant leaves like chemical fertilizer does and must be
applied sparingly to soil. It provokes a marked and vigorous growth
response. Two or three gallons of dry, pure fresh chicken manure are
sufficient nutrition to GROW about 100 square feet of vegetables in
raised beds to the maximum.
Exclusively incorporating pure chicken manure into a vegetable
garden also results in rapid humus loss, just as though chemical
fertilizers were used. Any fertilizing substance with a C/N below
that of stabilized humus, be it a chemical or a natural substance,
accelerates the decline in soil organic matter. That is because
nitrate nitrogen, the key to constructing all protein, is usually
the main factor limiting the population of soil microorganisms. When
the nitrate level of soil is significantly increased, microbe
populations increase proportionately and proceeds to eat organic
matter at an accelerated rate.
That is why small amounts of chemical fertilizer applied to soil
that still contains a reasonable amount of humus has such a powerful
effect. Not only does the fertilizer itself stimulate the growth of
plants, but fertilizer increases the microbial population. More
microbes accelerate the breakdown of humus and even more plant
nutrients are released as organic matter decays. And that is why
holistic farmers and gardeners mistakenly criticize chemical
fertilizers as being directly destructive of soil microbes.
Actually, all fertilizers, chemical or organic, _indirectly_ harm
soil life, first increasing their populations to unsustainable
levels that drop off markedly once enough organic matter has been
eaten. Unless, of course, the organic matter is replaced.
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.
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.