It happens every year. Following the spring melt and rains, an expanse of the Gulf of Mexico near the mouth of the Mississippi River becomes not a dead man’s zone, but rather a dead sea zone. Nutrients that wash off agricultural fields, i.e., fertilizer, is among the many contributors to blooms of algae and phytoplankton that deplete the water of most of its oxygen. The result is a “dead zone,” an area largely devoid of sea life.
Using what is known as a Soil and Water Assessment Tool (SWAT), scientists with the University of Tennessee Institute of Agriculture have modeled what would happen if Tennessee soybean and corn farmers incorporated an unfertilized winter wheat cover crop into their annual crop rotations. The model results indicate significant reductions in the amount of nitrogen and total phosphorus lost from row crop fields, thus reducing the Tennessee portion of the Mississippi River nutrient load that contributes to the dead zone in the northern Gulf of Mexico.
Shawn Hawkins, an associate professor in the Biosystems Engineering and Soil Science Department, and Hannah McClellan, a research associate working with Hawkins, used a SWAT water quality model to evaluate the nutrient load reduction for winter wheat cover crops on corn and soybean fields in both the Red River and South Fork of the Obion River watersheds in Tennessee. SWAT is a simulation model that links hydrology and nutrient cycling with crop growth.
The two introduced elevation data, crop satellite imagery (Croplands Data Layer), and soils data into the SWAT model and included Tennessee rainfall inputs to calibrate nutrient discharge into the rivers. Crop management schedules (such as planting, fertilizer applications and harvesting) were established in consultation with corn and soybean producers and included modifications of three important soil parameters resulting from the current adoption of contour and no-till planting, which together have already substantially reduced nutrient losses from agricultural fields in Tennessee.
The model predicts that incorporation of an unfertilized winter wheat cover crop on all of the row crop fields in the Red River and South Fork of the Obion River watersheds would result in substantial upland loss reductions of total nitrogen (30-50 percent) and total phosphorus (12-32 percent).
Efforts are underway in many states within the Mississippi River basin to reduce crop nutrient loss.
“I believe this is a method of first choice for our row crop producers to help reduce nutrient loss from the row crop fields within our state,” said Hawkins. “And it carries the added benefit of additional field erosion protection that complements nicely with no-till crop production.”
Hawkins and McClellan will discuss their findings with farmers at the UT Institute of Agriculture’s Milan No-Till Field Day scheduled for July 28 at UT’s AgResearch and Education Center in Milan. Billed as the nation’s largest no-till field day, researchers from Tennessee and other regional institutions present to farmers the latest management techniques to keep their farms profitable and sustainable through no-till and minimum tillage that “saves the soil” by sparing the plow.
The work was funded by the Tennessee Department of Environment and Conservation.
Through its mission of research, teaching and extension, the University of Tennessee Institute of Agriculture touches lives and provides Real.
Source:tennessee.edu