Drainage water management displayed Aug. 1 - 2 in Hillsdale, Mich.
Water control structures have a niche on heavy clay soils and no-till when watery manure is applied.
Farm drainage has made Midwestern agriculture lands productive, no doubt about that. But today we are hearing more about management to protect surface water quality.
Drainage water management is the practice of using a water control structure in a subsurface tile with the ability to control, or even stop water from leaving the outlet. These structures are being discussed as options to raise the subsurface drain outlets before liquid manure applications are made in late summer and fall. The goal is to slow drainage and reduce the risk of liquid manures reaching surface waters. The following information is from Bulletin WQ-44, Drainage Water Management for the Midwest by a team of researchers lead by Dr. Jane Frankenberger at Purdue.
Water control structures are of primary interest to reduce nitrates from reaching surface waters. Research has shown that they range in success of reducing nitrate losses from 15 to 75 percent. This wide range also shows how variable location, climate, soil types and cropping practices can be.
Managing a water control structure to raise the water level of the outlet creates a situation where the liquid is more apt to be held on the soil surface, in the soil or in the subsurface drain system. This creates a micro climate around the drain tile that is saturated. This saturated can reduce nitrates by one of three methods: 1) flooded soil creates denitrification resulting in nitrate lost to the air, 2) creates deep seepage or 3) reduces the volume of drainage that ever leaves the field by reabsorbing both water and nutrients back into the soil.
In manured fields, water control devices have their place, especially with clay soils that crack when dry, long term no-till and when very thin manures are applied.
There are many different soil types that respond differently to drainage. If yours is the type that cracks during late summer dry periods it is probably also the kind of soil that provides a very small window of opportunity to haul manure without creating soil compaction or ruts. When the late summer dry season create an ideal time to haul manure but soils may be cracked, water control devices may be a nice fit and add a safety net to protect water quality by stopping manure from reaching drain tile outlets and cause manure nutrients to be adsorbed by the soil.
Another fit for water control devices may be no-till fields. Long term no-till will have excellent pore spaces and macro pores from both worms and decaying roots. These macro pores may be conduits to subsurface drainage. Water control devices may be excellent control mechanisms in these situations also.
Manure that has had a lot of water added, either from adding runoff water or milking waste water to the manure storage, is more apt to act like water, and therefore, more apt to be a concern for reaching subsurface drainage systems. In livestock systems with a very thin/watery manure stream, these water control devices may provide an added protection to surface waters.
But these are not the only options and could be combined with other management practices. Tillage that disrupts the soil cracks and or macro pores has been effective in reducing liquid manure from reaching tile drains. Tillage, done ahead of manure applications, can disrupt macro-pores and break up clay soils, thus slowing the water flow to sub surface drainage and providing more opportunity for manure to be retained in the soil rather than going to drain tiles.
To learn when, where and how water control devices will fit into your farm and to see various tillage systems attend the Farm Drainage and Nutrient Management Field Day Aug. 1 - 2, 2012 in Hillsdale County, Mich. Professional tile drain contractors will be demonstrating installations and researches and practitioners will be on hand to address questions. Visit the Michigan Chapter of the Land Improvement Contractors of America website for full details. Events will be repeated both days.
Management of the water control devices is critical to achieve the desired goals with manure applications. Water control structures in sub surface drainage should be considered a complimentary practice after all other management practices have been fine-tuned and when specific soil and management conditions merit them. For complete details please refer to Drainage water management for the Midwest, bulletin WQ-44.