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Earthworms beneficial to crop productionBy David G. Hallauer, Meadowlark District Extension Agent At the recent Crops School in Nortonville, Kan., DeAnn Presley, K-State professor of soil and water conservation, shared a little bit about earthworms. Now I'll be the first to admit that earthworms aren't necessarily the topic first and foremost on my mind when I think about crop production in general or soils specifically. Even so, they're present and can have great value. For starters, they stimulate microbial activity. Earthworms consume microbes and studies indicate you'll find many more microorganisms present in their feces or casts than what they consume (gut). Studies also indicate that available plant nutrients (N, P, and K) tend to be higher in fresh earthworm casts than soil. They also mix soil, some would say similar to a plow. Infiltration is increased. Burrows persist and are conduits for water, particularly under heavy rainfall. Water holding capacity is improved with the increases in soil porosity and aggregation work they do. The channels they provide are prime for root growth, and lined with readily available nutrients. Earthworms also bury and shred plant residue, incorporating nutrients and reducing stratification. Do you have enough earthworms? Hard to say, and a lot of other factors can "negate" their efforts. But if you'd like to have some sort of measure to go by, Presley suggests the following: Excavate one cubic foot of soil in one piece when the soil surface is about 50 degrees. Count the worms or cocoons. Ten or more is usually associated with very healthy soils. Counts from one to nine are moderate. Less than one worm per cubic foot typically indicates the soil is very degraded.
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