Iowa State scientists team up to keep nitrates on fields

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Keeping nitrogen fertilizer on farm fields, to support optimum crop growth, and out of streams and rivers is no simple formula. It's complex.

"Think 'writing a novel' versus 'writing a recipe,' " said Matthew Helmers, an associate professor of agricultural and biosystems engineering at Iowa State University, where he is working with teams of scientists who are field-testing promising strategies, using a systems approach.

Whether present naturally in the soil or added during chemical fertilizer application, nitrogen not taken up by crops can move with water flowing through soil during rains and snow melt, and into streams and rivers where excess nitrogen can cause adverse health and ecological effects.

To address the issue of nitrogen and other farm nutrients leaving farm fields, ISU scientists, including Helmers, worked with scientists from the USDA-ARS, USDA-NRCS, the Iowa Department of Agriculture and Land Stewardship, and the Iowa Department of Natural Resources on the Iowa Nutrient Reduction Strategy Science Assessment, which was finalized in May.

The Science Assessment highlighted that the state's nonpoint source nitrate reduction goal of 41 percent becomes attainable only when the problem and the solutions are seen through a wide lens of interconnected ecological and social systems, which present a multitude of opportunities to minimize loss, said Helmers.

"When we look at in-field and edge of field opportunities, for example, we can start by doing the best job we can, putting the right amount of nitrogen on as close as possible to when the crop needs it," said Helmers.

Helmers leads ISU's Ag Water Management Research Group, which is a multi-tiered effort to study and analyze the impact of agricultural management practices on surface and subsurface drainage.

He also is a principal investigator on the field research team of the Climate and Corn-based Cropping Systems Coordinated Agricultural Project, also known as the Sustainable Corn Project. It's a 10-university research project in the Midwest, funded by the USDA and led by Iowa State.

Team members are gathering and analyzing field trial data from 35 field sites and thousands of farmers in eight Midwestern states in an effort to create a suite of practices that make corn-based cropping systems more resilient in response to climate change. The project includes field trials of practices, such as cover crops, which have the potential to reduce soil and nutrient losses under saturated soil conditions.

Some of his colleagues on the Sustainable Corn team are testing fertilizer application done with equipment that senses the nitrogen needs of each plant and adjusts the rate of application accordingly.

Applying nitrogen fertilizer in the "right amount and at the right time" is an essential step, but not enough, said Helmers, who sees opportunities for reduction "with every input and output of the cropping system." Results from field trials have made him a staunch supporter of cover crops, which can hold nitrogen in the soil.

"The Science Assessment showed that cover crops can reduce nitrate transport by approximately 31 percent. They are going to have to be a major player, if we want to reduce nutrient loading to water bodies downstream of row crops," said Helmers.

Other opportunities to reduce nitrate transport can be seen when studying what happens when water flows through and out of a cropping system.

"In some areas we may be able to manage or treat the outflow from the subsurface drained landscape with practices like drainage water management, subsurface drainage bioreactors, wetlands or the emerging practice of saturated buffers," said Helmers.

To be successful and reduce unintended consequences, Helmers says related social and economic systems also need to be included. The Sustainable Corn research teams include social scientists, rural economists, extension specialists, farmers and farm advisors in addition to crop, soil and climate scientists.

"We need to understand the agronomic side, the impacts of climate change, pests and pathogens and all of the economics of the practices we're testing," Helmers said.

"The cropping system has to be profitable and we have to help farmers understand how to manage it and work with them to implement and figure out what works on their farm. Only this broad systems approach is going to be effective in helping us solve our water quality problems."

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Iowa  |  December, 06, 2013 at 08:44 AM

The question I have is I put a total nitrogen lbs on for 200 bushel corn yield. corn following beans so I credit beans with giving me 40 units of nitrogen. 10 lbs worth in starter. 50 gals of 28% incorporated with a field cultivator with preplant chemicals and thats it no sidedressing. This fall in northeast Iowa with the tremendous rain in the spring after I had my corn planted before most of the heavy rains and a lot of my neighbors did not get all of their corn planted. I still got 190 bushel corn. So why do the so called sceintists say I lost my nitrogen. In northeast Iowa our soils are shallow if you do not put fertilizer on you will get very poor yields.

Veronica Lack    
Cedar River Watershed  |  December, 13, 2013 at 12:46 PM

Why is the USDA-NRCS offices promoting "French Drains" to farmers in Iowa where ever a wet spot or swale produces less corn when there is no legal drainage outlet for those spots? My and my neighbors wells Downstream from a group of farmers with no legal Drainage outlet for Cedar (W) Township Section 10 in Mitchell County were polluted by their digging ditches to sinkholes in Section 10 and then into Section 11 which drains into a Designated National Wetland with at least 6 Big sinkholes. This is another example of Point Source polluting and the state of Iowa and the Iowa DNR are not enforcing the 16 Iowa Drainage Laws and the Clean Water Act against the Point Source polluters. That causes deaths first in our animals then my husbands and my families health issues, and neighbors Downstream using the aquifers in this on-going pollution plume. This is the reason behind my Civil Rights Suit filed about a week ago against the State of Iowa and the IDNR. Anhydrous Ammonia kills at the levels they have polluted our drinking water with, and the Very high nitrates like Atrazine and high lead. I am a sustainable farmer that knows no one should Point Source pollute and was harrassed starting when I first complained to the IDNR in 1993. I have spent over $150,000 to stay in compliance with my Corps of Enghineer's Agreement, and the male polluters got the IDNR to charge me with Blockage of Water, and they took 42 acres of my farm to build a flood drain to drain their Wetland. We need Mandatory Nutrient Reduction Strategies now and we need to strictly penalize and stop the on-going polluters and keep the Iowa DNR from hiding the growing levels of Anhydrous Ammonia in our state's rivers, streams, and aquifers.

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