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Heed soil status when irrigating manure

Michigan livestock farms are catching and storing more manure containing a high amount of rain and resulting runoff in an effort to protect surface water quality around the farmsteads. As a result, more irrigation systems have been installed to land-apply these manure streams. The basic principles of manure application correlate to manure irrigation plus some additional safeguards.

Generally, these manure streams are very low in nutrients and percent solids. When based on agronomic land base needs, the gallonage of water that may be calculated is probably much higher than what the land can absorb, intake and hold without creating runoff, ponding or releases through tile drain systems. Since the initial goal of capturing the runoff and manure was to protect surface waters, farmers should remain mindful of that goal when irrigating with these systems.

Manure and soil should be tested, but current soil condition is the limiting factor for irrigation rates. Timing and soil moisture conditions are even more important. Be sure the current soil moisture is low enough that it can handle additional water without runoff or leaching. The irrigation should not travel over, nor the end gun reach any sensitive areas such as wetlands, neighbor’s property, roads or ditches. Any conservation practices in the fields, such as grassed waterways that are conduits to surface water, should not receive irrigation.

Key Points

• Irrigated manure requires a few additional safeguards.

• Be sure soil moisture is low enough to handle extra water without runoff.

• On tile-drained fields, check the outlets before, during and after all applications.

Tile-drained fields are not typically irrigated, but due to catchment of runoff and rainwaters, this is not always true. Irrigated fields need additional precautions to be sure they can take in the irrigation without pushing manure to the tile drains.

Be sure not to irrigate a field where runoff occurs and travels to any surface water inlets. Whenever applying manure to tile-drained fields, check the outlets before, during and after all applications.

If there is water flowing, do not apply manure. If manure begins to reach tile and flow, cease applications immediately and have tile blocks ready to utilize.

Most irrigation systems can be controlled for speed and resulting volume of application. Running the system several times at lower application rates may cost more, but results in safer applications. Using a cover crop during the fall and spring on a field you know will need to be utilized for manure irrigation can also provide greater infiltration and uptake of the watery manure.

Running low-disturbance tillage over a compacted soil layer ahead of irrigation can also assist in less runoff on fields with a compacted surface layer after a winter of snow and rain on the surface.

All fields should be assessed for the ability of infiltration and water-holding capacity before any manure application, but especially so when irrigating manure.

Rector writes from Michigan State University Extension.

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irrigating manure: Be sure not to irrigate a field where runoff occurs and travels to any surface water inlets.

This article published in the August, 2012 edition of MICHIGAN FARMER.

All rights reserved. Copyright Farm Progress Cos. 2012.