NAPRA Problem

25 points
Due November 10

A farmer in the southern part of Tippecanoe County recently had his well tested for the presence of nutrients and pesticides. Low concentrations of atrazine and moderate concentrations of nitrate were detected in the well sample. The well is located near the farmer's house that is surrounded by an 80 acre field that is in continuous corn. The farmer would like to determine if this field is likely responsible for the pesticides and nitrates that were detected in his well. Use the NAPRA Web tool to provide advice (select the Use NAPRA Crop Rotation link).

The field has an Alvin soil (IN157AtB2 Alvin) and is cropped in continuous corn (Select Tippecanoe in the NASIS box – leave STATSGO with the default settings). The corn is typically planted about May 5 and harvested October 1. The tillage system used is fall chisel plow with spring disk prior to planting. Atrazine is surface applied at 1.45 lb per acre of active ingredient at planting time. The residue cover at the time of herbicide application is approximately 20 percent. Anhydrous ammonia is injected approximately April 25 each year at 135 lb/ac. A starter fertilizer (10-34-0) is injected at planting time at 50 lb/ac. The farmer injects 3,000 gallons per acre of liquid swine manure on approximately October 20 each year. The effective rooting depth is 35 inches, the land use is row crops (SR - straight row), and the hydrologic condition is good.

Examine the pesticide and nitrate loading and concentration in annual percolation graphs (this is the simulated mass and concentration of pesticide leached below the root zone annually that may reach groundwater). Determine the mass and concentration of pesticide and nitrate leaching below the root zone at 10%, 50% and 90% probabilities. Determine the pesticide and nitrate loading and concentration in annual runoff too for the 10%, 50% and 90% probabilities.

In the output options section of the NAPRA interface, select "No Toxicity" for the Toxicity Type.

Is the field likely responsible for the problem? Prepare a brief report supporting your answer including the probability plots to support your answer. Briefly discuss your observations and your rationale for likelihood that this field is responsible for the groundwater quality concern.

Are your observations different if the soil is Crosby (IN157CwB2 Crosby)? Explain and provide supporting model output.

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