Using gleams and REMM to estimate nutrient movement from a spray field andthrough a riparian forest

With the increased number of large animal production facilities in eastern North Carolina, nutrient accumulation is becoming a problem in surface wate rs and groundwater. To protect these water sources, management practices to reduce nutrient movement or accumulation are being evaluated using compute r 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 nu trients through a riparian buffer zone from an agricultural field that rece ived swine lagoon effluent. The models simulated annual application rates o f effluent equivalent to 500 and 1000 kg N/ha. The GLEAMS model provided th e weather data and nutrient concentrations in the soil, sediment, and leach ate for input into REMM. Assuming a 1000 kg N/ha loading rate, GLEAMS month ly average NO3-N leachate concentrations were within 14% of the observed da ta, and REMM-simulated NO3-N leachate concentration was within 5% of the ob served data. Both models provided an adequate estimation of nitrogen transp ort through the system. GLEAMS simulations of PO4-P leachate followed the g eneral trend of observed data. However, there was no apparent response in s imulated PO4-P leachate concentrations for the two loading rates (95 and 19 0 kg P/ha), indicating a problem in the phosphorus calculations in the mode l. The REMM-simulated PO4-P leachate was greater than observed concentratio ns and was affected by the inputs obtained from GLEAMS. The pre-release ver sion of REMM provided good estimates of the nutrient transport, and with a few improvements, official releases of REMM have the potential to provide b etter estimates of nutrient movement through the riparian buffer zone.