Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Proceedings
Publication Acceptance Date: 7/29/2005
Publication Date: 7/29/2005
Citation: Feyereisen, G.W., Sands, G.R., Wilson, B.N., Strock, J.S., Porter, P.M. 2005. A simple model to estimate artificial subsurface drainage losses. In: Proceedings of American Society of Agricultural Engineers. ASAE Paper No. 052024. Interpretive Summary: A zone of oxygen-depleted waters in the Gulf of Mexico at the mouths of the Missisppi and Atchafalaya Rivers has been observed for several years, disrupting marine life in the associated coastal region. Nitrogen carried by the Mississippi River into the Gulf has been identified as a contributor to the problem of low oxygen. Nitrogen is exported from agricultural fields through the artificial subsurface drainage systems. One method of reducing field export of nitrogen is to grow a winter cover crop between the time of fall corn harvest and spring sowing of soybeans. The effectiveness of this method is highly dependent on the weather during the October-May timeframe. Computer simulation models provide a means of estimating the effectiveness of proposed methods over a long time frame. A soil-plant-atmosphere model, RyeGro, was developed to estimate the effectiveness of a fall-sown cereal rye cover crop to reduce field subsurface drainage nitrogen losses. This paper describes how the soil moisture, subsurface drainage, and nitrogen cycle submodels in RyeGro work. The model was calibrated using three years of weather, soil moisture, soil nitrogen, subsurface drainage flow, and subsurface drainage nitrogen loss data from a three-year experiment on a corn-rye-soybean crop rotation conducted at Lamberton, Minnesota. The model was validated with two years of data for a corn-soybean crop rotation from an earlier study conducted on the same plots. The model predicted drainage volumes within one mm (1%) and 39 mm (23%) of the measured values for the validation years. Although the model contains a simple soil temperature / freeze component, difficulty was experienced matching the timing of drainage events in the late winter / early spring period.
Technical Abstract: The potential of winter cover crops to reduce nitrate nitrogen (nitrate-N) loading from artificial subsurface drainage systems is being researched in the Northern Corn Belt. A soil-plant-atmosphere simulation model, RyeGro, was developed to investigate the efficacy of winter rye over the long term. This paper describes the soil water balance and subsurface drainage component of RyeGro. The soil water component provides an estimate of infiltration, average soil moisture content, and subsurface drainage over the fall-spring drainage season. The model was purposely kept simple, with the soil represented as a series of tanks. Holtan’s infiltration scheme was used to divide precipitation into runoff and infiltration components. Model calibration was performed with data from a field study in southwestern Minnesota. Validation was executed using data from previous work done on the same field plots. The model predicted drainage volumes within one mm (1%) and 39 mm (23%) of the measured values for the validation years. Although the model contains a simple soil temperature / freeze component, difficulty was experienced matching the timing of drainage events in the late winter / early spring period. The model uses basic soil properties as inputs and has few parameters to calibrate, facilitating ease of use and application to other locations.