Aside from the humus content, are “worm castings” any more nutritious than regular compost?
Yes! As material in a compost heap decays (becoming humus), the various nutrients undergo chemical changes, which make them more accessible to plants. In addition to this process, however, worms also reduce the overall volume of the material even further as they remove the ingredients necessary for their own survival, growth, and reproduction (mainly bacteria, rotifers, etc.) Thus, with the remaining substances compacted into less volume, the actual nutrient percentages rise accordingly. It has been noted by several researchers that earthworm casts usually contain more “total and nitrate nitrogen, organic matter, total and exchangeable magnesium, available phosphorus, base capacity, and moisture equivalent” than their surrounding environment.”–(C.A. Edwards and J.R. Lofty, in “Biology of Earthworms”, 1977, p.201) This fact should hold true whether the surrounding environment is soil, manure, kitchen waste, or whatever.
