Livestock producers and commercial manure applicators need to be extra cautious when applying liquid manure to dry farm fields this fall. While it may seem that dry fields can absorb larger amounts of liquid manure, there are other soil conditions that you need to consider, according to Amanda Meddles and Glen Arnold, Ohio State University.
Deep cracks in the soil as well as worm holes can create a pathway directly to subsurface drainage. When injecting manure on 30-inch centers, remember that manure is being applied at much greater volume directly behind the injectors than the soil may be capable of absorbing. If excess manure is applied there is an increased risk that the manure will move offsite and contaminate water.
Manure reaching field tile through soil cracks, worm holes and other direct conduits is referred to as preferential flow. Taking measures to prevent manure from reaching tile outlets is crucial to avoid contamination of water bodies. Meddles and Arnold suggest producers consider using lower rates and covering the fields twice.
Any measure of disturbing the soil will aid in keeping manure nutrients in the root zone. This can be tillage equipment that works the ground 3 to 5 inches deep prior to application, or injection equipment that disturbs the soil below the line of manure injection. With tillage, be sure the equipment leaves at least a 90 percent residue cover.
Sometimes it can only take seconds for manure to reach tile lines. Checking for manure flow immediately, as well as throughout the next 24 hours, is recommended depending on how dry the tile is and how far the outlet is from the site of application. Tile plugs and control structures can be used to ensure manure does not exit outlets or to stop manure that is already flowing.
For more details on preferential flow, go to http://bit.ly/Pu9XyI .
The Iowa Department of Natural Resources also has dry-weather manure application tips online at http://tinyurl.com/96dxya2.