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.

GROWing the plant

One of the things I enjoy most while gardening is GROWing some of my plants.  I don’t GROW them all because there is no point in having giant parsley or making the corn patch get one foot taller.  Making everything get as large as possible wouldn’t result in maximum nutrition either.  But just for fun, how about a 100-plus-pound pumpkin?  A twenty-pound savoy cabbage?  A cauliflower sixteen inches in diameter?  An eight-inch diameter beet?  Now that’s GROWing!

Here’s how.  Simply remove as many growth limiters as possible and watch the plant’s own efforts take over.  One of the best examples I’ve ever seen of how this works was in a neighbor’s backyard greenhouse.  This retired welder liked his liquor.  Having more time than money and little respect for legal absurdities, he had constructed a small stainless steel pot still, fermented his own mash, and made a harsh, hangover-producing whiskey from grain and cane sugar that Appalachians call “popskull.”  To encourage rapid fermentation, his mashing barrel was kept in the warm greenhouse.  The bubbling brew gave off large quantities of carbon dioxide gas.

The rest of his greenhouse was filled with green herbs that flowered fragrantly in September.  Most of them were four or five feet tall but those plants on the end housing the mash barrel were seven feet tall and twice as bushy.  Why?  Because the normal level of atmospheric CO2 actually limits plant growth.