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On-farm research has been a way of life for Grand Meadow area farmer Wayne DeWall. His dad did his own comparisons, and Wayne has carried on the tradition for nearly 40 years. In recent years his interest in on-farm research has expanded and intensified with the help of CHS agronomists and a Minnesota Department of Agriculture (MDA) researcher.

"I've compared liquid fertilizer versus dry and various application rates, as well as comparing split applications to 100 percent preplant to find the best rate and application timing," says DeWall. "CHS Rochester does soil sampling on a three-acre grid, and my agronomist Emily Drinkall makes recommendations on how much phosphorus (P) and potash (K) to apply. They then make variable rate applications accordingly."

About nine years ago, DeWall added another resource to his research efforts when he joined the Root River Field to Stream Partnership. Funded by a variety of agencies and organizations, and led by the MDA, the partnership carries out farm-based research and monitoring of water quality and edge-of-field runoff of water and sediment, as well as nitrogen and phosphorus, in several watersheds feeding into the Root River.

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Wayne DeWall (center), Kevin Kuehner, MDA agronomist and researcher (left) and Root River Field To Stream Partnership technician Ron Meiners (right) pause at the edge-of-field monitoring station in DeWall's field. Data collected at this station over many years is now informing on-farm management decisions throughout the region. Photo credit (this photo and background): Paula Mohr, for The Farmer

When Kevin Kuehner with the MDA knocked on his door, DeWall agreed to take part in the project that included a runoff monitoring station. "We had a perfect location for it, and we also had a drain tile nearby," says DeWall. "The drain tile emptied into a ditch where they could monitor subsurface nitrogen loss, as well as how often and when the tile line ran. Kuehner explained that anytime the water was flowing, we could be losing nitrogen, even in the winter."

DeWall also began working with Kuehner, the University of Minnesota and CHS on in-field plots looking at various nitrogen rates and timing practices. Plots looked at seven preplant rates and three timing treatments. Applications ranged from 0 to 180 pounds of nitrogen (N) per acre applied in 30 lb N/ac increments and each are replicated four times.

"Kevin lays out the plots each year, and we work with them," says Drinkall. "He gives me the locations, and when we do our applications, I ensure rates correspond in the plots."

Drinkall notes that like DeWall, most of the CHS patrons she works with utilize grid sampling and variable rate applications of P & K. Many also use nitrogen stabilizers on their urea, UAN and anhydrous to reduce leaching and volatilization, keeping it in the soil for the crop to use.

"They realize that with our wet springs and heavy rains, applied nitrogen is at risk," says Drinkall. "Every acre needs to be treated individually, but we try to encourage split N application where possible. We find that combined with variable rate phosphorus, lime and potassium application, it provides the most agronomic benefit."

Drinkall emphasizes the need for as much information as possible, thus the grid sampling. DeWall's involvement in the Root River Field to Stream Partnership is giving him even more data and is impacting how he farms.

"We are able to see how much sediment and nitrogen we are losing and when it occurs. The monitoring shows our biggest runoff happens when the ground is still frozen," says DeWall. However, this is not when we see the most amount of sediment and nutrient loss. About 60% of the sediment, phosphorus and nitrogen loss measured occurred in May and June."

Baseline monitoring was conducted on DeWall's’s field from 2011-2016. Starting in 2017 DeWall began to make changes accordingly. He reduced fall tillage to the use of a ripper, eliminated fall nitrogen applications and put in targeted pollinator habitat/filter strips alongside his private drainage ditch side inlets and the fence line where the monitoring station is installed.

"We had a good catch last year with the pollinator habitat/filter strip," says DeWall. "It's about 60 feet wide and not quite half a mile long. We expect it to be fully established in about three years."

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After baseline monitoring was conducted on DeWall's field from 2011-2016, he made changes. In addition to reducing fall tillage to the use of a ripper and eliminating fall nitrogen applications, he put in targeted pollinator habitat/filter strips along private drainage ditch side inlets and the fence line where the monitoring station is installed.

He also put in a new waterway and revamped some older ones. It didn't take long to begin seeing the effects. "Sediment runoff has been cut down, and nitrogen losses have been reduced," says DeWall. "For nitrogen, we've gone to split applications with a lower preplant rate and sidedressing at V4 when the plant needs and will take up more nitrogen. Our data shows it is agronomically more feasible. Putting everything on preplant was overspending."

Kuehner points to potential savings demonstrated by DeWall’s plot in 2018 when average corn yields following soybeans, peaked at 218 bushels per acre. "The economic return to fertilizer N (when using average 2018 fertilizer and corn prices) was greatest when about 160 lb N/ac was applied just before planting. This rate includes all sources of nitrogen including starter and credits from MAP and AMS.

However, when nitrogen was split applied, the 120 lb N/acre split rate treatment provided the greatest return on investment. When compared to a 180 lb/ac preplant rate, which is a common rate when corn follows soybeans, profits could have been improved by $16/acre, even when factoring in the extra cost of the in-season nitrogen application. Rainfall was 50-80% above normal in May and June last year and was a major reason why the split nitrogen rate performed so well.”

"We need additional years of data, but these experiments are signaling that slightly reduced N rates when split applied are more profitable on Wayne’s farm and result in less loss from the sub-surface drain tile system," says Kuehner.


"Preliminary water quality monitoring results indicate that the six-year baseline nitrate load of 36 lb N/ac measured from the sub-surface drain tile has been reduced by 19%."

After three years of similar data, DeWall dialed back his rates and started split applying. However, he has continued with the plots, and new data reinforces his move. "On our test plots last year, we saw our best yield of 220 bushels (at 17.6% moisture) on a test plot with only 120 lbs. N applied in a 30/90 split," says DeWall. "When factoring in the nitrogen and drying cost, our net return on that plot was $623 per acre."

DeWall sees more changes ahead. "First we want to see if the practices continue to reduce N loss and sediment runoff," he says. "Possibly we will go to even less tillage, and we may try cover crops. We need to do what we can. We use the water resource, whether for swimming, fishing or drinking. We need to protect it."

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