Farm Progress Reports




Northeast Research and Demonstration Farm


Agricultural and Biosystems Engineering


Woodchip bioreactors are an effective tool for reducing nitrate in tile drainage leaving farm fields. Bioreactors are a recognized tool in the Iowa Nutrient Reduction Strategy to reduce total nitrogen loads by 45 percent. Decades of field and lab experiments have helped determine major factors driving bioreactor performance including residence time, temperature, and age. Reported removal rates across and within experiments varies significantly, in the range of 2–22 g N/m3/d. Traditional methods of measuring bioreactor performance have relied on infrequent sampling at the bioreactor inlet and outlet. Biweekly or flow-weighted sampling of field bioreactors provides low resolution data on nitrate concentrations, introducing uncertainty when estimating performance. Observing internal processes can help improve bioreactor design for increased efficiency. A novel sampling system coupled with state-of-the-art field sensors was used for the first time to obtain high-frequency in-situ nitrate measurements in a field bioreactor at the Northeast Research and Demonstration Farm in Nashua, Iowa.





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