DES MOINES (DTN)--Some farmers in Ohio learned how easily liquid manure can pollute waterways and kill fish.
Frank Gibbs, a Natural Resources Conservation Service soil scientist, armed himself with smoke bombs and a homemade blower to prove his point at the Farm Science Review agricultural trade show in mid-September in central Ohio.
Liquid manure acts like rain on a field and can work its way into the ground via small hollowed holes, burrowed by earthworms. It can reach drainage tiles buried below then be carried out to ditches and eventually creeks.
To illustrate his point, Gibbs placed smoke bombs in front of a blower attached to a tile line buried in a soybean field. As farmers watched, the smoke almost instantly filtered up from the field through the earthworm holes.
Gibbs said that it has only been in the past five years that scientists have become aware of how liquid manure can pollute creeks by filtering through earthworm holes and cracks caused by drought.
Jim Hoorman, an Ohio State University Extension water quality and manure specialist, said such contamination has been a problem for about 15 years and is the leading source of fish kills in Ohio.
In the early 1990s, manure that is as liquid as water started being commonly applied to fields. This liquid manure typically comes from large dairy and hog farms with lagoons where solids and liquids of manure separate. Farmers are left with manure that is almost all liquid.
Hoorman said even solid manure can create problems if spread on a field before a heavy rain.
Both scientists recommended lightly tilling fields before manure is spread. Working the ground even slightly can clog earthworm holes with soil, preventing manure from seeping down into them.
At the farm show, farmers also saw demonstrations of a $100,000 manure spreader that tills fields as it spreads manure.