From 2014–2016, members of Illinois C-BMP engaged in a three-year program with Springfield City, Water Light & Power and the Sangamon County SWCD to reduce nitrate levels in Lake Springfield. This targeted BMP program included nitrogen rate trials, N-WATCH™ soil nitrate sampling, use of cover crops, and water quality testing in the tributaries that feed the lake.
In 2016, after three years of nitrogen rate studies in the Lake Springfield watershed as part of this partnership, the University of Illinois developed a maximum return to nitrogen system specifically tailored for that watershed. MRTN, which is supported by land grant universities, converts corn yield responses in rate trials to economic return responses and recommends the most profitable range of nitrogen application rates for farmers to use. This system provides a reliable recommendation so that nitrogen rates neither exceed what the plants need nor fall short of the amount needed to reach the optimum yield and economic return on the nitrogen investment.
The Lake Springfield MRTN led to a recommended decrease of 5–8 pounds of nitrogen per acre for corn (following soybeans) compared to the central Illinois MRTN recommendation. With thousands of acres of corn grown in this watershed each year, this reduction in recommended application rate represents a significant savings to the farmer and minimizes the potential for excess nitrogen loss to the lake. The Lake Springfield MRTN is available online in the Illinois section of the MRTN calculator website located at http://cnrc.agron.iastate.edu/. This program’s first year is 2016 and its progress will be included in the next biennial report.
