Controlling nutrient loss

Gloria Hafemeister
Now Media Group


Protecting the soil and preventing nutrient losses is obviously on the minds of farmers, according to the attendance at the recent Discovery Farms meeting in Watertown.

About 35 people attended the meeting to learn more about ways to prevent soil and nutrient run-off and make the best of the nutrients in the manure on their farms.

The Discovery Farms program works with operating commercial Wisconsin farms to conduct on-farm systems research, evaluations and demonstrations. Participating Discovery Farms program farms span the state's diverse soil types; physical and water characteristics; and livestock and cropping systems.

Amber Raddatz, co-director of the program, said Discovery Farms cooperators work hard to establish baseline data that can be used to determine environmental impacts of various farm management practices. Many projects evaluate nutrient management (manure) strategies and practices aimed at reducing nonpoint source pollution, with the ultimate goal of protecting a clean water supply today and in the future for people and animals.

'Through this program, we monitor how much water leaves a field and what's in it,' Raddatz said. 'We monitor sites for five to seven years so we can get through all the crop rotations and a variety of weather conditions.'

While the research has shown that runoff is considerably higher in March, she said runoff doesn't occur every time it rains. Soil saturation at the time of a rain is a big factor.

'Discovery Farms data show that it's not the size of the farm operation that matters — it's the management that matters when it comes to water-quality protection,' Radatz said.

Radatz said on-farm data taken by Discovery Farms shows the more soil you lose, the more phosphorus you lose. About 1 pound of phosphorus is lost with every 1,000 pounds of soil. Nitrogen losses are a different story because they do not leave with soil, but instead, they leach through the soil.

Soil loss occurs the most from April through June, Radatz said. That's because it is when the soil has more moisture in it and when rain will likely run off.

'That's where cover crops are helpful,' she said. 'Even if you didn't have a lot of growth in fall, remember it's really not for fall protection, it's more for spring.'

No-till part of solution

No-tilling is one method of holding soil in place but she cautioned, 'You need other practices in combination with it.

'No till does a good job of absorbing phosphorus in the growing season, but dissolved phosphorus losses will be high in no-till in winter because it's built up on the surface.'

During those spring months, no-tillers should scout their fields and investigate where water flows. Look for areas where there's sedimentation in field corners or soil covering small seedlings — signs of in-field movement, Radatz said.

'If you're already using no-till in those areas, then consider adding waterways or dams to keep soil from moving,' she added.

Discovery Farms' research shows that when soil is frozen, particulate runoff doesn't occur because there's no soil movement. But they can still see a loss in dissolved phosphorus. This loss happens when applications are made right before a runoff event.

Timing important

By better timing the applications, she said, growers can reduce those losses by two to four times.

Discovery Farms looked at phosphorus loss on several farms in Vernon County in Wisconsin. Two of the farms were no-tilled, and another incorporated manure. The disturbance caused by the incorporation was similar to a chisel plow, Radatz said.

Their data showed that the farmer using manure incorporation was able to keep his dissolved phosphorus losses very low, the lowest of all the farms. But when they looked at total phosphorus loss, which includes particulate phosphorus, it was a different story.

There wasn't much difference in total phosphorus loss compared to dissolved phosphorus loss for the no-tillers, but the farmer doing incorporation saw a very high amount of total phosphorus lost one year because he lost a lot of soil.

'Soil is complicated,' Radatz said. 'There is so much involved, so results do not show one single thing that influences yield or prevents runoff. Our goal is to determine the best management practice for particular conditions.'