Iowa farmers use “water quality toolbox”

Proven practices find success on Iowa farms, benefit downstream neighbors


By Dan Looker, IAWA Writer

Iowa (IAWA) – Seven years ago Jon Bakehouse of Hastings, Iowa, started planting cover crops where he grows corn and soybeans with his father. Switching to no-till farming in the 1990s improved water filtration in wet spots on their West Nishnabotna River valley fields–but not enough.

So they decided to try using cover crops. As the name implies, they’re plants that cover and protect the ground. Bakehouse seeds cereal rye on more than 300 acres after corn harvest in the fall. Following winter, the rye regrows before he sprays it with herbicides and plants soybeans in the spring.

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Their soil has responded.  After a one-inch rain last February, “the water on our ground disappeared in a day,” Bakehouse said. On nearby farms without cover crops, water lingered longer.

“Water and how to get rid of it–that’s how we started using cover crops,” Bakehouse said.

Building healthier soil is one reason more farmers like Bakehouse are using cover crops. Another is that cover crops are an excellent tool for improving water quality under the Iowa Nutrient Reduction Strategy. It aims to lower nitrogen (N) and phosphorous (P) entering streams by 45percent and 29 percent respectively.

In the Strategy’s first decade, cover crop acreage surged from almost nothing to nearly 3 million acres—roughly a tenth of Iowa’s cropland. Cover crops are just one tool for cleaning water. And, like a thin drill bit that can snap, practices in Iowa’s toolbox have strengths and weaknesses. Here’s a closer look:

Cover Crops

They reduce N and P reaching streams by about 30%, according to Iowa State University researchers Mike Castellano and Matt Helmers.  (Good management and weather can put reductions above 45%.) Many tools control mainly nitrogen or phosphorus. Cover crops reduce both. Their roots capture nitrates (a form of N) and also slow soil erosion, keeping phosphates (a type of P) in place.

A big plus–farmers themselves gain.  Almost immediately, cover crops slow erosion and cool soil against summer heat. Slowing erosion means keeping expensive soil on the farm.  Long term, cover crops build soil organic matter, bringing resilience to both drought and downpours. Less immediately, farmers can also see better yields and less money spent on certain inputs.

Some minuses–cover crops aren’t easy to get started.  Last year Bakehouse spent almost $12,000 on rye seed for 300 acres. Government and private grants can defray costs, but not permanently. Bakehouse hasn’t used grants. Complications include finding labor, machinery and time to plant cover crops near a busy harvest. Bakehouse’s retired sister seeds their cover crops.

“For cover crops, the management requirements go up, and that’s a challenge,” he said.

If not done correctly – which is difficult when trying for the first time – cover crops can also negatively impact yields. It’s a major adjustment with some trial and error, though worthwhile for most farms.

Edge-of-Field Practices

These practices slow drainage tile water as it leaves a field, giving microbes time to “digest” nitrates. They work only on nitrogen. There are many such practices. Bioreactors and saturated buffers are two kinds expected to ramp up in the coming years.

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A bioreactor is a deep trench filled with wood chips. A pipe diverts tile water into it. Saturated buffers are extra drainage tiles that parallel a stream, diverting water into soil under bankside grass. Unlike cover crops, they’re easier to manage and farmers don’t have to change how they grow crops. Yet, farmers also receive limited benefits.

There are only about 230 of these structures in Iowa, according to the Iowa Department of Agriculture and Land Stewardship (IDALS). Interest is growing, however, because edge-of-field tools work well. According to ISU nutrient reduction experts Helmers and Castellano, both bioreactors and saturated buffers can reduce nitrate runoff by up to half.

Recently, some Iowa counties and cities have taken a “batch and build” approach to simplify construction of edge-of-field practices. County teams find groups of farmers in one area with an interest, then do all the backend paperwork and engineering. Grants and project partners pay for 100 percent of the installation. Now Iowa is installing 100+ every year.

No-till farming and other soil conservation

Stopping tillage keeps corn stalks and soybean stems on the surface, protecting land from erosion. So do terraces, farm ponds and other conservation practices farmers have used for decades. Because P sticks to soil particles, these practices lower the amount reaching streams, says ISU researcher Matt Helmers.

An upward trend continues. In five years, from 2017 to 2021, no-till increased from 7.7 million acres to 9.5 million acres ahead of corn and soybeans—more than 40% of total acreage for those crops, according to a survey conducted by the Iowa Nutrient Research and Education Council.

Other tools

These are among the most important tools for managing Iowa’s nutrients. There are scores of others, including more timely application of manure and fertilizers. Crops use up most of that fertilizer, so efficient use alone won’t get Iowa to its goal of a 45% cut in nutrients, said. Castellano.  

“But it’s an easy first step because it can increase profitability as well as the environmental benefits,” he said.

There are also wetlands, prairie strips, and crop rotations.

Back in Iowa’s Nishnabotna Valley, Jon Bakehouse says that as he gets older, he’s taking a broader view of his farm in the world. He’s on the board of Practical Farmers of Iowa, a 6,300-member group that researches the fine points of sustainable farming. He is a member of the Iowa Soybean Association, which has monitored clean water practices on farms since the 1980s.

“We’re among those responsible for the nutrient load in the Gulf of Mexico,” he says. “Whatever we can do, we should.”

Published on March 31, 2023