Start Date: Sep 01, 2009
End Date: Aug 31, 2013
The goal of this research is to evaluate water quality impacts of organically-managed agricultural systems in tile-drained regions of the upper Midwest. Thirty plots (30.5 m W x 32.0 m L) will be established within a 25 ha field at the ISU Agronomy and Ag Engineering Research Farm that has been transitioning to certified organic management since 2006, under oat/alfalfa. The infrastructure for evaluating subsurface tile drain water quality and quantity and soil water content within each plot will be installed in the summer 2010. Tile drain water samples will be collected to evaluate drain water quantity and quality starting in spring of 2011, and will continue for the duration of the experiment. Soil sensors will be installed in each plot at 5, 15, 30, and 50 cm depths to evaluate soil water content, plant-available water, salinity and temperature. Soil fertility status will be quantified for each plot in spring 2011. Soil cores (to 120 cm) will be taken every spring and fall in 2011, 2012, and 2013, to evaluate soil profile N, P, and C distributions. Surface soil cores (0-5 cm and 5-15 cm) will be removed in late fall 2010-2013, to assess soil biological, chemical, and physical changes during establishment of organic systems. Three organic cropping systems (C-S-O/A-A, C-S-WW/clover, and continuous pasture) and a conventional C-S rotation will be established in the spring of 2011. All phases of all rotations will be present every year. Composted animal manure will be used as the nutrient source in the organic plots and 28% UAN in the conventional corn plots. Weeds will be managed using a rotary hoe and cultivator in organic plots and herbicide in conventional plots. Crop yield and residue N, C, and P content will be quantified for all crops every year for the duration of the experiment. Nutrient and water budgets will be calculated for each cropping rotation. The RZWQM- model will be used to simulate water and N movement, crop growth, and C and N cycling. Model predictions of tile drain N leaching will be compared with measured values.