USING GLEAMS AND REMM TO ESTIMATE NUTRIENT MOVEMENT FROM A SPRAY FIELD AND THROUGH A RIPARIAN FOREST

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With the increased number of large animal production facilities in eastern North Carolina, nutrient accumulation is becoming a problem in surface waters and groundwater. To protect these water sources, management practices to reduce nutrient movement or accumulation are being evaluated using computer models. The computer models, Groundwater Loading Effects of Agricultural Management Systems (GLEAMS) and a version of Riparian Ecosystem Management Model (REMM), were used to estimate nitrogen and phosphorus transport of nutrients through a riparian buffer zone from an agricultural field that received swine lagoon effluent. The models simulated annual application rates of effluent equivalent to 500 and 1000 kg N/ha. The GLEAMS model provided the weather data and nutrient concentrations in the soil, sediment, and leachate for input into REMM. Assuming a 1000 kg N/ha loading rate, GLEAMS monthly average NO3 –N leachate concentrations were within 14% of the observed data, and REMM–simulated NO3 –N leachate concentration was within 5% of the observed data. Both models provided an adequate estimation of nitrogen transport through the system. GLEAMS simulations of PO4 –P leachate followed the general trend of observed data. However, there was no apparent response in simulated PO4 –P leachate concentrations for the two loading rates (95 and 190 kg P/ha), indicating a problem in the phosphorus calculations in the model. The REMM–simulated PO4 –P leachate was greater than observed concentrations and was affected by the inputs obtained from GLEAMS. The pre–release version of REMM provided good estimates of the nutrient transport, and with a few improvements, official releases of REMM have the potential to provide better estimates of nutrient movement through the riparian buffer zone.