EVALUATING CROP YIELD AND WATER QUALITY IMPACTS OF NITROGEN MANAGEMENT, COVER CROPS AND LIVING MULCHES IN IRRIGATED CORN AND SOYBEANS
Every week, over two-hundred water samples are pulled from suction tube lysimeters that span across three 535x60 ft test plots at the Rosholt Research Farm. All lysimeters along the fields are placed at depths ranging from four to six feet below the surface. Each field section has a uniform coarse-textured soil type. However, all plots explore a different row crop and rotation, along with a different fertilizer application rate. The east section is soybean-corn, the central section is corn-soybean, and the west is corn-corn.
Due to the susceptible soil type at the Rosholt site, nitrogen studies are a primary focus. Following sample collection, nitrogen analysis is run on each individual water sample. Nitrate levels are determined using a HACH spectrophotometer model DR6000. A HACH spectrophotometer gives nitrogen concentrations by reading wavelengths that pass through the sample as it funnels through the vial within the machine. Through pre-programmed software, wavelengths are converted into concentrations. These values give an idea of groundwater nitrate levels across the plots.
In addition to the suction tube lysimeters, data is also collected from drain gauges, barrel lysimeters, and rain gauges. Drain gauges are used to measure the volume of water draining into groundwater. The water samples pulled from the drain gauges are also analyzed for nitrates. This information is considered when studying how leaching affects nitrate concentrations. For a related study led by the University of Minnesota, water samples are also collected from barrel lysimeters that are buried within the soil profile throughout the plots. These open cylindrical containers accumulate water as it filters through the ground. Similar to samples pulled from the drain gauges, volumes and nitrate concentrations are also taken from the barrel lysimeter water samples. Aside from nitrogen studies, irrigation studies are also being conducted at the Rosholt Research Farm. In order to determine when the irrigator should be run, rain gauges are used. Rain gauges provide precipitation amounts, indicating how much rainfall the soil is receiving.
Rosholt Field Day August 2017 Nitrogen Research -Click here to learn more about the research in 2017.
https://www.farmprogress.com/fertilizer/study-looks-two-cover-crops-potential-reduce-nitrate-leaching
https://blog-crop-news.extension.umn.edu/2020/10/nitrogen-study-looks-at-two-cover-crops.html