JoAnne Skelly: Worm compost is an exceptional mulch

In cleaning up my bookshelves, I found a Rodale Press booklet written in 1937 called “Our Friend, the Earthworm” by Dr. George Sheffield Oliver. Dr. Oliver was one of the first researchers and educators in the U.S. to teach farmers and gardeners how to optimize soil health and garden productivity with earthworms. Charles Darwin’s comment, “Earthworms, the most important animal in the world” was his motto and the title of one of his many books. He felt these invertebrate animals were critical to good soil and healthy food.

To those who don’t understand a productive soil, calling mere worms the most important animal may seem a stretch.

“Yet few creatures equal the burrowing earthworm as a necessity to better health and greater growth to plant and vegetable life, and, therefore, indirectly of utmost importance to man, ” Oliver wrote in 1937. Oliver called the earthworm, “Nature’s own plough, her chemist, her cultivator, her fertilizer, her distributor of plant food.”

Earthworms feed on soil, dead organic and vegetable matter (such as leaves and old roots), animal matter and manure as food. All the materials they eat pass through their digestive system and come out as castings – “worm manure.” Worm castings are soluble and are immediately available as plant nutrients. Plants benefit when the worms leave their castings in the root zone where they can be readily absorbed. Castings often contain five to 11 times more nitrogen, phosphorous and potassium, major plant nutrient requirements, than surrounding soil or traditional compost.

Oliver felt that orchardists, truck farmers, home gardeners and nurserymen could benefit from adding earthworms to soil “as a natural cultivator and fertilizer.” Organic farmers today work diligently building up earthworm populations in their soil by supplying them with moist soil loaded with organic matter and other food sources.

However, earthworms have many enemies such as birds, moles, toads, centipedes, millipedes, fly maggots and their greatest enemy, ants. Most insecticides kill earthworms. Redwood shavings and sawdust kill earthworms. Lack of moisture kills worms. Nevada’s dry soil low in organic matter makes it challenging for gardeners trying to build up worm populations.

Worm compost makes an exceptional mulch and soil conditioner, in addition to being an excellent source of nutrients for plants. It is a first-rate potting mix for container plants and for starting seeds. It also can be used to top-dress a lawn. A good resource on worm composting (vermicomposting) is http://aces.nmsu.edu/pubs/_h/H164.pdf from New Mexico State University Cooperative Extension.

JoAnne Skelly is the Carson City/Storey County Extension educator for University of Nevada Cooperative Extension and may be reached at skellyj@unce.unr.edu or 887-2252.