It is not possible for me to tell you how well your own homemade
compost will fertilize plants. Like home-brewed beer and home-baked
bread you can be certain that your compost may be the equal of or
superior to almost any commercially made product and certainly will
be better fertilizer than the high carbon result of municipal solid
waste composting. But first, let's consider two semi-philosophical
questions, "good for what?" and "poor as what?"
Any compost is a "social good" if it conserves energy, saves space
in landfills and returns some nutrients and organic matter to the
soil, whether for lawns, ornamental plantings, or vegetable gardens.
Compared to the fertilizer you would have purchased in its place,
any homemade compost will be a financial gain unless you buy
expensive motor-powered grinding equipment to produce only small
quantities.
Making compost is also a "personal good." For a few hours a year,
composting gets you outside with a manure fork in your hand, working
up a sweat. You intentionally participate in a natural cycle: the
endless rotation of carbon from air to organic matter in the form of
plants, to animals, and finally all of it back into soil. You can
observe the miraculous increase in plant and soil health that
happens when you intensify and enrich that cycle of carbon on land
under your control.
So any compost is good compost. But will it be good fertilizer?
Answering that question is a lot harder: it depends on so many
factors. The growth response you'll get from compost depends on what
went into the heap, on how much nitrate nitrogen was lost as ammonia
during decomposition, on how completely decomposition was allowed to
proceed, and how much nitrate nitrogen was created by microbes
during ripening.
The growth response from compost also depends on the soil's
temperature. Just like every other biological process, the nutrients
in compost only GROW the plant when they decompose in the soil and
are released. Where summer is hot, where the average of day and
night temperatures are high, where soil temperatures reach 80 degree
for much of the frost-free season, organic matter rots really fast
and a little compost of average quality makes a huge increase in
plant growth. Where summer is cool and soil organic matter
decomposes slowly, poorer grades of compost have little immediate
effect, or worse, may temporarily interfere with plant growth.
Hotter soils are probably more desperate for organic matter and may
give you a marked growth response from even poor quality compost;
soils in cool climates naturally contain higher quantities of humus
and need to be stoked with more potent materials if high levels of
nutrients are to be released.
Compost is also reputed to make enormous improvements in the
workability, or tilth of the soil. This aspect of gardening is so
important and so widely misunderstood, especially by organic
gardeners, that most of Chapter Seven is devoted to considering the
roles of humus in the soil.