Conservation in action at research site

LEXINGTON, Ill. — The longest standing cover crop tile-drained research site in Illinois is finding solutions to reach the nutrient loss reduction strategy goals.

Shalamar Armstrong, Purdue University associate professor of agronomy, and Michael Ruffatti, Illinois State University crop and soil science lecturer, led a tour of the research site farmed by Philip Brown on the first stop of the From Farm to Filtration: A Tour of Conservation in Action.

Hosted by the McLean County Soil and Water Conservation District, Purdue, Illinois Nutrient Research and Education Council, The Nature Conservancy, and Illinois Sustainable Ag Partnership, the tour highlighted how drainage tile impacts water quality, cover crops’ role in nutrient management, utilizing wetlands to limit nutrient runoff, and the costs associated with treating nutrients in the water.

The primary goal of the Illinois Nutrient Loss Reduction Strategy is a 45% reduction in both nitrogen and total phosphorus loads, with interim targets set at a 15% nitrogen decrease and a 25% total phosphorus decrease by this year.

The objective of the research near Lexington is to determine the impact of nitrogen application timing and cover crops on cash crop yield and nitrate nitrogen loss in a tile-drained landscape. The cover crop is a mix of cereal rye (92%) and daikon radish (8%).

The living laboratory research also utilizes the 4Rs of right source, rate, time, and place to keep nutrients on and in the field.

Treatments

Over the last 10 years, several treatment interactions of cover crops and nitrogen management have been examined.

Initially, the impact of nitrogen application timing (fall and spring applied N fertilizer) and cover crops on tile water quality was examined. Recently, researchers have investigated precision planted cereal rye and the inclusion of balansa clover on tile water quality.

The data include non-cover crop, cover crop, and zero control categories.

“Over six corn years and four soybean years, there was a 43% reduction in the amount of nitrate that’s leaving the field on average with corn and a 52% reduction behind soybeans compared to using no cover crops,” Armstrong said.

There are three series of plots totaling over 20 acres. Each of the 15 1.6-acre plots have five treatments that are replicated three times in every series. The large-scale research was designed to include all soil types and deviations in a field.

“Each plot is individually drained with 45-foot laterals. The laterals come together and go through a control drainage structure,” said Ruffatti, who began working at the site as a graduate student with Armstrong about 10 years ago.

“The control drainage structure takes all of the water from the plot and the equipment can measure the water level, velocity and temperature. All that information is being collected by this equipment.”

A solar-powered automated water sampling station collects leachate samples following rainfall events from the individual subsurface drainage systems for each experimental plot. The samples are taken to a lab, then filtered and analyzed colorimetrically for nitrate and ammonia concentrations.

“We want to see how our practices are influencing the tile water leaving the field, so we don’t want tile water coming from other parts of the field. We’re isolating the portions of this field that we’re using these treatments on, and then monitoring that water,” Ruffatti said.

“All of the data is collected remotely gets sent to a server back on campus. I can check that server for my phone or computer. The samples are sent to the lab at Purdue to determine nitrate and phosphorous levels.

“Once we have the nutrient data where we know how much nitrate and phosphorous is in the sample and we know how much water is leaving the field, we can calculate a load to determine how much total nitrogen and phosphorous leave the field from each of the plots.

“We’re tracking this 24/7 throughout the year to see if we’re making an impact.”

“All this equipment is helping us monitor and track how these practices we’re doing and are they actually going to work to achieve goals that we’re trying to accomplish for reducing nitrate and phosphorus losses from waters in Illinois. This is all field-scale research using full-size equipment,” Armstrong noted.

In addition, the research also found that cover crops over time are reducing the volume of water or drainage that’s leaving through subsurface tile drainage.

“Cover crops reduce the inorganic nitrogen that’s susceptible to being lost by tile,” Armstrong said.

The trials found 23% less discharge through tile drainage with corn and soybeans plus the cereal rye mix compared to fields without cover crops.

The study is also looking at how much the cover crop seeding rate can be reduced while still achieving over a 50% reduction in nitrate loss.

Takeaways

Adding cereal rye did not affect soybean yield.

Corn yields were reduced by cereal rye in years of elevated cereal rye growth and nitrogen uptake and nitrogen tie-up. This yield reduction can be overcome by adaptive management such as adding starter fertilizer at planting, late season nitrogen application (V10 growth stage), and precision planting cover crops.

Despite nitrogen fertilizer application timing (fall or spring), adding cereal rye to the system reduced nitrate loss by 46 to 49%.

As the cover crop system matures over time, the greater the nitrogen loss reduction via tile-drainage. In high organic matter soil with poor cash crop growth, it is possible to lose a significant portion of nitrate via tile-drainage.

Beginning

In 2014, the Illinois Nutrient Research and Education Council awarded funding to Armstrong to initiate the Nitrogen Management Research Field Station.

The overreaching goal of the NMRFS site is to address critical nutrient loss reduction questions through investigating the impact of 4R nitrogen management and in-field sustainable practices such as cover crops on cash crop yield and nitrogen and phosphorous loss in a tile-drained landscape.

“Over the past 10 years, this site had been awarded $1.45 million in funding in order to keep this going,” Armstrong said.

“I can’t say precisely how many students we’ve trained. There have been those who have seen the site and those who just experienced the data and wrote their thesis from the data.

“The data from this site has been cited and used in over 10 policy publications, meaning that we were able to influence regional, probably state policy, based on our findings.

“And I would say that over very easily over 10,000 farmers have experienced or have heard a presentation from this data. So, I want to just take time to thank NREC, the Brown family, and all of you who have advocated for this site.”

Data for each of the last 10 years of research can be found at ag.purdue.edu/agry/armstrong-sendlab/lrr.