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Biomass Harvest and Nutrient Management Systems Impacts on Water Quality
YEAR: 2008
INVESTIGATORS: Antonio P. Mallarino, Matthew Helmers

Excess sediment, phosphorus (P) and nitrogen (N) impair the majority of Iowa lakes and many streams also are impaired during some periods of the year. Most sediment and nutrients originate from agricultural fields or stream banks. A good potential for large-scale bioenergy production in Iowa is challenging researchers and nutrient management planners to develop crop and nutrient management systems to maximize production of feed, fuel, and fiber while utilizing soil and nutrient resources minimizing undesirable environmental impacts. Therefore, there is a need for studies of soil processes and nutrient loss on a field-plot scale that represent actual field conditions as much as possible focusing on bioenergy production and nutrient management systems likely to be adopted soon. The project will evaluate and compare systems that will still predominate for years to come in Iowa (such as corn and soybean for grain production) and new systems with likely adoption for bioenergy production (such as total or partial corn and perennial grass biomass harvest) managed with fertilizer or liquid swine manure. The study results will provide needed information about cropping and management systems for bioenergy production impacts on soil and water quality that can be compared to impacts from currently used systems. The proposed work will integrate efforts by scientists from the Department of Agronomy and the Department of Agricultural and Biosystems Engineering, by the ISU Research and Demonstration Farms System, a group of Northwest Iowa farmers (the Northwest Iowa Experimental Association), and seed funding by the IFLM program of IDALS. These contributions plus requested funding from the Iowa Water Center will be used to develop work during 2008 and 2009 at a runoff study site in Northwest Iowa and a tile-drainage study site in Central Iowa. We propose to study how crops, biomass harvesting systems, fertilizer and manure management practices, and selected soil properties relate to loss of sediment and various forms of N and P with surface runoff and subsurface tile drainage. The main objectives are (1) to determine dissolved reactive P, total dissolved P, algal-available P, total P, and total N concentrations and loads in surface runoff from corn production systems harvested for grain using different tillage and fertilizer or manure P management systems and from continuous corn harvested for grain and cornstalks and (2) to determine loss of nitrate, dissolved reactive P, and total dissolved P through subsurface tile drainage from crops for selected bioenergy production systems managed with fertilizer or manure N-P management systems. We will also analyze soil and harvested biomass for nutrient concentration and relate these results to treatment effects on N and P loss. Overall, the information from the study will be useful to establish new and improved environmentally oriented management guidelines and will provide useful information concerning impacts of anticipated land changes in the near future on export of nutrients to water resources.