Tom Richard
Cornell University School of Composting Experience has taught me that if using conventional chemical fertilizer, use approximately 1/2 as much nitrogen as normal and turn pile every 2 to 3 weeks. More fertilizer is added at each turning. Adding the full amount of nitrogen all at once will cause the pile to overheat. Blood Meal can cause the pile to overheat in some cases, but not to the extent that chemical fertilizer will and the conditions must be favorable. Slow-release chemical fertilizer does not appear to have this problem. In either case, it is a worthwhile venture in order to make full use of the fall leaves that would decompose very slowly otherwise. I have experienced such slow decomposition with leaves due to a lack of nitrogen that odors were a problem and the pile heated very little. When using primarily leaves, I have found that by adding an inch of straw for every 3 to 4 inches of leaves greatly improved aeration and drainage issues. |
When composting high carbon materials such as leaves, additional nitrogen may be required to reduce the C/N ratio to the optimal range. If considering using fertilizer as an N source, one needs to proceed cautiously. While the theoretical number should be the same as calculated using the C/N ratio (see Carbon/Nitrogen Table) formulas, the nitrogen in fertilizers is released much more rapidly than that in organic nitrogen (from which the rules of thumb are derived). Organic nitrogen sources provide a natural "time release" that makes them available at a rate comparable to the growth rate of microorganisms in the compost, so they are utilized efficiently. The rapid availability of nitrogen fertilizers is especially a concern in the fall and winter, when low temperatures slow down the growth rate of microorganisms, and nitrogen uptake will be correspondingly slow. To mimic a natural time release with synthetic fertilizers, they should be applied sparingly and in a series of applications. While there is not a research base on which to estimate what the right rate would be, sniffing for ammonia volatilization may indicate if too much was applied too soon. In addition, because none of the fertilizer nitrogen is locked into compounds that are difficult to degrade (as is the case with organic sources), the total applied should be significantly less than the calculations indicate - perhaps half to two thirds. Back To Top |
