Discover what's leaving the field

CANNON FALLS, Minn. — Discovery Farms Minnesota recently completed its fourth year of data collection on its first farm.

CANNON FALLS — Discovery Farms Minnesota recently completed its fourth year of data collection on its first farm.

"It's actual numbers," said George Rehm, Discovery Farms coordinator and University of Minnesota soil science professor emeritus. "We're taking actual measurements — we're not using models — to find out what's coming from agricultural land."

What Discovery Farms Minnesota has found is "everything's related to precipitation and what we do," Rehm said.

In 2014, there were 11 Discovery Farms located throughout Minnesota's agricultural zone. The farms were selected to be representative of agriculture in their particular area. Farms include turkey, swine, dairy and beef production as well as corn, soybeans, alfalfa, sugarbeets, wheat, dry beans and canning crops. Nine have subsurface tile; two do not.

In water year 2014, which was Oct. 1, 2013, through Oct. 1, 2014, median annual precipitation was 0.41 inches below normal across all sites, with a range of 2.22 inches below normal to 6.76 inches above normal. Most of the rainfall fell in June, with rainfall averaging more than 3 inches above normal for that month.


July was nearly a mirror opposite, with rainfall coming in at 2 inches below normal.

Rainfall was also an inch or more above normal in October 2013, April 2014 and May 2014.

Across the Discovery Farms Minnesota network, 38 percent of the annual surface runoff occurred during frozen soil conditions, which is lower than in past years. Even with a large snowpack, the gradual warm up, lack of frost and dry soils allowed much of the snowmelt to infiltrate the soil profile.

Only 10 percent of subsurface tile drainage was observed during frozen soil conditions, most subsurface tile drainage occurred from April to June.

On average, 9 percent of annual precipitation left monitored fields as surface runoff during an average of 12 days and 15 percent left in subsurface tile with an average of 121 days of flow.

Soil loss in 2014 was similar to past years. The most critical time for soil loss is between planting and when crop canopy is established. Almost all of the surface runoff was in May and June.

The range in annual soil loss from surface runoff was 47 pounds per acre to 1,923 pounds per acre. The median was 307 pounds per acre. Median soil loss from subsurface tile drainage was 12 pounds per acre, with a range of 3.1 to 145 pounds per acre. The top was from a farm with a broken tile that he can't find, Rehm said.

Phosphorus loss in 2014 was similar to results from past years, Rehm said. Discovery Farms Minnesota tracks total phosphorus loss, including particulate phosphorus, which is attached to soil, and dissolved phosphorus, which is not attached to soil.


Median total phosphorus loss from surface runoff was 0.8 pounds per acre, with a range from 0.4 to 3.1 pounds per acre. Median total phosphorus loss from tile drainage was 0.1 pounds per acre, with a range from 0 to 0.8 pounds per acre. Two-thirds of the annual total phosphorus loss occurred in May and June in the particulate form. In March, 18 percent of total annual phosphorus was lost, primarily in the form of dissolved phosphorus.

Total nitrogen loss, which includes organic, ammonia and nitrate nitrogen, primarily occurs through tile drainage. Median total nitrogen lost from tile was 24 pounds per acre, with a range from 2.4 to 59 pounds per acre. Almost all the nitrogen lost via tile lines was in the nitrate nitrogen form. Most of the nitrate was lost in June, followed by May and April.

Median total nitrogen loss from surface runoff was 4.2 pounds per acre, with a range from 1.8 to 23 pounds per acre. Most nitrogen loss from the surface was in the organic nitrogen form. Total nitrogen concentrations were similar to past years, but total losses were higher because of more tile drainage.

"Agriculture gets really blasted, undeservingly so in my opinion," Rehm said, when it comes to water quality concerns.

The worst offenders are using excessive rates of nitrogen, be it manure or commercial fertilizer or a combination of the two.

Discovery Farms is about knowing what's happening on the ground, rather than guessing. The farmers they have approached are eager learners.

Their attitude has been "I want to know what's leaving my land and if it's not right I'll change it," Rehm said.

At Discovery Farms Minnesota, researchers record what agronomic practices the farmer is using, soil texture, tillage and manure history. After each water year is completed, they meet with the farmers to go over the results. Farmers may ask for ideas on how to improve their operations.


"Discovery Farms is like a family, we have a problem child," Rehm said. The farmer is aware of the issues and will make changes when his financial situation allows.

The organization's study is too young to make tillage comparisons. Discovery Farms Minnesota also has the challenge of not having different types of tillage practices on the same soil type with the same slope, but it may be able to draw conclusions by looking at similar soil in Wisconsin. Discovery Farms Minnesota was patterned after a similar program in Wisconsin.

Rehm said it's important to remember it's impossible to achieve zero runoff. Even in a pristine pine forest or a pristine southwestern Minnesota prairie, there are nitrates moving below the root zone. There is no silver bullet, rather using best management practices is the best way to reduce nitrogen, phosphorus and sediment loss.

"In Minnesota, agriculture's so diversified as so much depends on the production practices the producer is using and the environment," he said.

Producers can find all sorts of experts, but they need to find credible sources to guide them as they seek to implement best management practices suited to their crop, soil type, slope, tillage system and rainfall. Producers need to know the people they are getting their advice from, Rehm said.

Overall, he said the data show that while there are opportunities for improvement, there are many good practices in place.

"Farmers are doing a pretty good job keeping soil on the landscape," Rehm said.

So far this water year, there has been little precipitation and little runoff. Discovery Farms Minnesota is continuing to grow and has added an irrigated farm to its family.

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