Maintaining tile systems to prevent nutrient loss
OCONOMOWOC – When it rains a lot or there's a lot of snow melt, farmers are especially happy to have tile systems that help them get into the fields on time in spring.
Drainage systems improve the timeliness of field operations, enhance growing conditions for crop production, increase crop yields on poorly drained soils and reduce yield variability.
In addition, drain tiles can improve soil quality by decreasing soil erosion and compaction.
Discovery Farms has looked extensively at drainage tiling systems on farms all across Wisconsin and Minnesota. Eric Cooley of the UW-Discovery Farms program shared the findings of the on-farm studies with about 80 producers at the recent Farmers for Lake Country Ag Resource Conference in Oconomowoc.
Cooley said that wet soils take five times as much heat to warm than dried soil. Tiles are important in managing fields but they need to be monitored and maintained.
“Proper management in tile drained landscapes is key to reducing nutrient losses,” he said. “It is less expensive to maintain the tiles and prevent losses and more effective than it is to treat the water at the end of the pipe.”
Cooley recommends an annual inspection of systems, looking for blowouts in the field or blockages at the outlets.
“It’s easy to identify a blowout in spring,” he said. “Walk in the field and listen; you can actually hear the sucking. In some cases you will see bubbling. The ground where a blowout occurs is like a sink hole in the field.”
If left untreated, Cooley said blowouts can get extremely larger.
He says there are many reasons for blowouts including old tiles (such as clay or concrete) breaking, separation of tiles, and inadequate venting. Venting problems often occur because of adding more tile without properly sizing them or changing the vent system to accommodate the increased volume.
Manure on tiled land
Cooley stresses the importance of assessing soil conditions prior to manure application, especially liquid manure.
Wet, saturated soil will result in leaching of nutrients as well as dry, hard cracked soil.
“Review the forecasted weather prior to liquid manure application,” he said. “Worm burrows and old root channels provide direct paths to the tile with little or no filtration. Applying the manure on a living cover or higher residue field or increasing the amount of solids in the manure will help prevent nutrients from getting into these channels.”
Cooley said that knife injection will not completely prevent manure from getting into the pores.
“Sweep injection helps but if the sweeps are too close together or if you drive too fast the manure will go into the pores by finding the path of least resistance,” he cautions. “Look at the types of sweeps available and which will work best or consider pre-tilling to close the pores.”
The biggest challenge is managing low-solids liquid manure, Cooley said, adding that the problem with solids on the surface, however, is that more phosphorus sits on the top layer of the soil. It is not a problem initially but when it rains it carries the phosphorous excess directly through the cracks and burrows.
Role of the tiles
Cooley says, “We don’t see surface water runoff in fields unless the tiles are flowing at capacity. Tiles are good at getting water away without carrying nutrients with the water.”
Some farms have in-field inlets but he cautions that they can act like a blowout in the event of a hard rain. Those utilizing these needs to check after a rain because nutrients can get in through them.
So what can a farmer do to prevent nutrient losses?
“Apply nutrients based on your nutrient management plan," Cooley said. "Delay or split nitrogen fertilizer applications, waiting to apply manure or anhydrous ammonia in fall until the soil temperature is less than fifty degrees.”
He stresses, “If you apply manure right after the silage is off, the soil is too warm and nutrients will move into the tile or ground water. The longer you wait for soil to cool down the more nutrients will still be there in the soil in spring when you need them.”
Those who need to apply manure right after silage removal should establish a cover crop to hold the nutrients, he added.
Regarding cover crops, he says, “If you want to do fall applications get something out there growing and then apply the manure. You can even put on a couple thousand gallons and plant into it, letting the water in the manure help to germinate the seed right away.”
A practice like this holds nitrogen in the soil profile, according to Cooley.
Finally, Cooleysaid its important to have an emergency plan in place
“If you see any manure coming out of tile lines call the emergency spill hotline and immediately block the flow of the discharge with bales or something to keep the discharge from advancing to a river or stream,” he said.