Tiling as a Tool to Manage Runoff

October 22, 2016 02:13 AM

Active stewardship helps Iowa farmer ensure his crops’ nutrients stay put

On his 135-year-old Iowa farm, Brent Kuehnast carries on a tradition of stewardship. Every one of his 3,500 acres has some form of tiling, with 30% of acres pattern tiled and other tile lines put in nearly 100 years ago. Nutrient runoff management is top of mind. Why? It makes sense with stricter regulations and tighter wallets.

“Farmers are spending $70 to $90 plus per acre on nitrogen. For us, it’s important to make sure that nitrogen stays put,” he says.

In addition to dollars lost, he and many farmers are aware what they do upstream has a direct effect downstream. Kuehnast and his family have used buffer strips for the past 25 years, perform soil and tissue tests and are looking into bioreactors and other practices to mitigate runoff into the Des Moines River.

Most of his buffer strips are 60' to 100' wide. He works with USDA to help offset costs and manage native grass. “They’ll help pay the cost of seeding and seed—typically a 10-year practice and they’ll have maintenance requirements also covered by cost share,” Kuehnast says. 

“I have buffer strips on every farm my family owns and 90% of our total farms,” he says.

If you’ve established a strong stand of native grasses the first year, the buffer strips will typically reseed themselves and likely only require one reseeding in the 10-year program. In Kuehnast’s case, he has the option to re-enroll at the end of each 10-year contract to keep receiving assistance.

Kuehnast also zeroes in on what goes into his fields through fertilizer timing and rate. Each year he performs tissue tests, and every three years he gathers soil samples.

“We do tissue testing around the first of June to test the live plant for levels of nitrogen, phosphorus, potassium, zinc, magnesium, etc., so we can get an idea if we’re deficient or long,” Kuehnast says.

If they’re short nutrients, he checks the field’s yield potential and applies what’s needed. If they’re long, he adjusts for potentially lower amounts of fertilizer or considers split fertilizer applications next year. 

Tissue testing shows what the crop is able to use but it might not account for the whole picture. Some nutrients work better together, such as sulfur and nitrogen. If your field is short sulfur to a level at which nitrogen uptake is affected, a tissue test might make you think you need to apply more nitrogen. If sulfur is the true culprit you’ve wasted money on excess nitrogen and still haven’t solved the deficiency problem. Kuehnast takes soil tests on a 2.2-acre grid.

Just like all facets of agriculture, technology continuously evolves, and so does tile-drainage management. While Kuehnast is happy with his current system, he is researching alternatives such as bioreactors to see if they’re a better fit on certain fields. 

Bioreactors act as a filter for water flowing out of tile drainage lines. They use woodchips as a medium in which to capture nutrients and avoid releasing them into other bodies of water. According to Keegan Kult, environment scientist at the Iowa Soybean Association, it costs about $8,000 to install one that manages 40 to 100 acres of tile. There are some cost-share options available, so check what’s available in your county.

Kult is working with a few farmers across the state to find best management practices for the new system. 

The pressure is on for farmers to address nutrient runoff as public awareness of water quality issues rises. Kuehnast says tile is a critical component of his yields and will do what it takes to keep using them.

“We need to maintain our tile system to have productive farm ground, so I want to stay ahead or prevent issues downstream,” he says.  

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