DECATUR, Ill. — The Illinois Soybean Association and the Illinois Fertilizer and Chemical Association came together to host a 4R Field Talk Sept. 5 at the Farm Progress Show site in Decatur.
The event included a variety of topics including cover crop selection and management, cover crop seeding application and reduced tile nitrate loss with 4R management and cover crops.Lowell Gentry, a retired University of Illinois principal research specialist, said the state of Illinois’ Nutrient Loss Reduction Strategy has a goal to reduce nitrogen and phosphorus loss by 45% by the year 2035. The strategy works with point source and non-point sources, the latter of which includes farms.
“When it comes to nitrate loss from fields it’s mostly from tile drainage, at least in our area,” Gentry said.
Gentry said tiles are important because they pay for themselves pretty quickly and they let farmers get into the fields earlier.
But they have a downside.
“Tiles are the conveyor of nitrates into streams, and in our area some of our streams are losing 25 pounds per acre per year,” Gentry said. He said researchers have been sampling the Embaras River at Camargo since 1993. The research group has been there 1,750 times over the last 30 years to get data.
That watershed is losing on average, 3 million pounds of nitrogen per year that goes down that small stream.
When it comes to phosphorus, Gentry said it is not a tile drainage problem, it is an overall runoff problem.
“There are times when we lose high-dissolve phosphorus but not high-particulate phosphorus,” he said.
In a replicated tile drainage study conducted in Douglas County, the objectives were to find out why and how nitrate is lost. They also were interested in seeing if they could improve nitrogen sufficiency with split application — applying it in the spring, side dress and fall for both soybeans and corn.
To start, they put on a full rate of 160-180 pounds of nitrogen per acre during the fall. Another treatment involved half in fall, 25% at planting and 25% at side dress. They used an inhibitor in the fall.
Another treatment was 75% rate to test for a yield difference. Two more involved nitrogen in spring and at side dress, and the final trial had cover crops.
“When we do bring the rate down from 100% in the fall to 50% in the fall, we reduce tile nitrate every time,” Gentry said.
The lowest tile nitrate came from the 50/50 split with cereal rye cover crop every other year in front of soybeans.
“We always get a significant reduction in tile nitrate if we grow at least a half of ton of above ground biomass,” Gentry said.
For corn strip-tilled with a cover crop, that is a half ton of biomass per acre.
Cereal rye grows very quickly and is fixing carbon.
“That little plant can exert so much good and reduce tile nitrate because it has a high percent nitrogen,” Gentry said.
Although not significant, split applied nitrogen tended to increase corn yield and decrease tile nitrate. Nitrogen treatments had no effect on soybean yields.
