Organic material containing a great deal of lignin, such as sawdust or wood shavings, presents a problem because usually its starch content is either limited or unavailable, and if nitrogen is supplied in large amounts, the lignin-protein conversion to humus is heavy. For this reason, sawdust and other woody fibers do not become available readily and should be considered as long-time amendments to the soil. Eventually the humus does break down, of course, but most gardeners are too impatient to wait for this effect.
OILS FOR HUMUS
Our plant originally plowed under has now released most of its elements to the soil. However, except for the lignin-protein, true humus formation has yet to take place. A major source of humus, surprisingly enough, is a portion of plant materials-fats, waxes, oils and resins-so often mentioned in British gardening literature as likely to ruin a compost pile. I was once told by a farmer that he wouldn't dare spread spoiled shell corn on his fields to rot because corn grain was so oily it would ruin his soil.
Like so many traditional but false ideas in agriculture and gardening, this notion was accepted without question. I believed it up to about twenty years ago, until one day I was lunching with Dr. Emil Truog, the very able head of the soils department at the University of Wisconsin. I mentioned I had thrown away some oil-soaked sawdust rather than add it to my compost pile. His only remark was "Why?" In the discussion that followed, I learned that here we are dealing with a half-truth-an observation not carried to a logical conclusion. It is true that as we watch dissolution of organic matter in a compost pile we do find that waxes, fats and resins are still intact at the end of the first year. It is, however, this very resistance to decay which makes them ideal elements in humus formation.
This does not mean the perfect compost pile is one made up of candles, rancid lard and spent crank-case oil. A pile composed entirely of fatty materials would never get started on decomposition. It does mean that we should not avoid including some oil, fatty or waxy wastes in making compost piles.
A point worth restating here is that all soil processes involve living organisms. When we attempt to study them by chemical analyses, the bacteria and fungi (even if not killed) are no longer in their normal environment. Thus tests are inaccurate. It is not surprising, therefore, to find the careful soil scientist using words such as "I feel that . . . ," "possibly," or "probably," far more often than positive, dogmatic words about the action and nature of organic matter.