Edward Osei

The Agricultural Policy Environmental EXtender (APEX) Model: An Emerging Tool for Landscape and Watershed Environmental Analyses

The Agricultural Policy Environmental eXtender (APEX) model was developed by the Blacklands Research and Extension Center in Temple, Texas. APEX is a flexible and dynamic tool that is capable of simulating a wide array of management practices, cropping systems, and other land use across a broad range of agricultural landscapes, including whole farms and small watersheds. The model can be configured for novel land management strategies, such as filter strip impacts on pollutant losses from upslope cropfields, intensive rotational grazing scenarios depicting movement of cows between paddocks, vegetated grassed waterways in combination with filter strip impacts, and land application of manure removal from livestock feedlots or waste storage ponds. A description of the APEX model is provided, including an overview of all the major components in the model. Applications of the model are then reviewed, starting with livestock manure and other management scenarios performed for Livestock and the Environment: A National Pilot Project (NPP), and then continuing with feedlot, pesticide, forestry, buffer strip, conservation practice, and other management or land use scenarios performed at the plot, field, watershed, or regional scale. The application descriptions include a summary of calibration and/or validation results obtained for the different NPP assessments as well as for other APEX simulation studies. Available APEX Geographic Information System–based or Windows-based interfaces are also described, as are forthcoming future improvements and additional research needs for the model.

Evaluating Nutrient Tracking Tool and simulated conservation practices

The Nutrient Tracking Tool (NTT) is an enhanced version of the Nitrogen Trading Tool, an earlier model that was developed by the USDA. NTT provides farmers, government officials, researchers, and others an efficient, web-based, and user-friendly method of evaluating the impacts of proposed and existing conservation practices (CPs) on water quality and quantity. In addition to cultural or nonstructural practices (e.g., nutrient management), commonly used structural CPs, such as filter strips, grassed waterways, cattle exclusion, terraces, and wetlands, can be evaluated in NTT with a few key strokes after selecting the users field of interest. NTT estimates the impacts of each practice, or combination of practices, on sediment losses, nutrient losses, and runoff, as well as farm production indicators such as crop yield. Through its interface with the Agricultural Policy Environmental eXtender (APEX) model (Williams and Izaurralde 2005), NTT simulates all CPs using rigorous algorithms while providing the user with a simple interface to access the results. The current and previous versions of NTT are available to users at the “Welcome” screen of the NTT website (http://nn.tarleton.edu/ntt). NTT was developed by linking APEX to its interface. APEX is thus the core simulation model of NTT and is an augmented version…

ENVIRONMENTAL AND ECONOMIC IMPACTS OF ALTERNATIVE MANAGEMENT SYSTEMS FOR THE MINERAL CREEK WATERSHED

The Maquoketa River drains 1,879 square miles of predominantly agricultural land in northeastern Iowa and is one of 13 tributaries of the Mississippi River that have been identified as contributing some of the highest levels of suspended sediments, nitrogen, and phosphorus to the Mississippi stream system. Initiatives focused on improving water quality have been implemented in several Maquoketa subwatersheds including the Mineral Creek Watershed (MCW), which covers over 12,000 ha in the west central portion of the Maquoketa River Watershed. A key component of the MCW water quality initiative was the application of an environmental and economic modeling system for over 20 different scenarios that include implementation of contouring, terracing, notill, and other practices on part or all of the MCW cropped acreage. Reductions in sediment, total N losses, and total P losses for 15 scenarios reported here were predicted to range from essentially zero to 52%, 0.3 to 26%, and 5 to 63%, respectively, relative to the baseline conditions. Aggregate impacts on producer net returns predicted across the entire watershed for the 15 scenarios as compared to the baseline ranged from an increase of

Macro-level analysis of CNMPs in the Ohio River Basin

14/acre to a decline of

Use of CEEOT-SWAPP Modeling System for Targeting and Evaluating Environmental Pollutants

19/acre.

Impacts Of Changing Herd Sizes On The Effects Of Manure Application Rates

The Comprehensive Economic and Environmental Optimization Tool – Macro Modeling System (CEEOT-MMS) was developed recently by researchers at the Texas Institute for Applied Environmental Research (TIAER) to help evaluate the implementation of agro-environmental policies or practices on large scales. CEEOT-MMS consists of a field-scale environmental model and a farm-level economic simulation model. Recently, CEEOT-MMS was applied to evaluate the impacts of alternative manure nutrient management options when implemented on all animal feeding operations (AFOs) in Texas. The model was also applied to study the impacts of changing herd sizes on the efficacy of various nutrient management practices, as well as the costs and effectiveness of implementing comprehensive nutrient management plans (CNMPs) on AFOs.

Estimating sediment and nutrient delivery ratios in the Big Sunflower Watershed using a multiple linear regression model

Field-scale and watershed-scale environmental models are only capable of simulating mechanistically a limited number of practices individually. Furthermore, there is need for a mechanism to simulate environmental and economic models within a unified interface program in order to determine cost-effective practices. This study was conducted to develop an automated program, SWAPP (Soil and Water Assessment Tool (SWAT)-Agricultural Policy/Environmental eXtender (APEX) Interface Program), to convert SWAT files to-and-from APEX format and simulate SWAT and APEX simultaneously; integrate SWAPP and an economic model (Farm-level Economic Model; FEM); and evaluate the resulting program (Comprehensive Economic and Environmental Optimization Tool-SWAPP; CEEOT-SWAPP) using measured data.

Use of CEEOT-SWAPP Modeling System for Cost-effective Targeting and Evaluation of Environmental Pollutants

The Comprehensive Economic and Environmental Optimization Tool - Macro Modeling System (CEEOT-MMS) was developed by researchers at the Texas Institute for Applied Environmental Research (TIAER) to help evaluate the implementation of agro-environmental policies or practices on large scales. Recently, CEEOT-MMS was applied to evaluate the impacts of three alternative manure nutrient management options when implemented on all animal feeding operations (AFOs) in Texas. The three manure nutrient management options were manure application at the nitrogen uptake rate of receiving crops, manure application to supply all of crop phosphorus (P) requirements with manure ortho-P (a High P rate), and manure application to supply all crop P needs with manure total P (a Low P rate).

Economic and environmental impacts of alternative practices on dairy farms in an agricultural watershed.

This study is part of an effort to analyze the nutrient load reductions obtained from current and future best management practices implementations in the Big Sunflower Watershed to meet the 45% nutrient reduction goal set for the watershed based on the US Environmental Protection Agency Science Advisory Boards (USEPA 2007) Gulf of Mexico hypoxia report. This paper describes the identification of dominant pollutant delivery mechanisms in the watershed, estimation of instream pollutant delivery ratios (DR) from subbasins to watershed outlet, and development of a tool to estimate changes in instream pollutant DR for what-if scenarios. The Big Sunflower Watershed is a 7,800 km2 intensively cultivated agricultural watershed in the State of Mississippi. The Comprehensive Environmental and Economic Optimization Tool (CEEOT) modeling system, consisting of the Soil and Water Assessment Tool (SWAT) and Agricultural Policy and Environmental Extender (APEX) models, was used to develop a multiple regression equation to estimate the sediment and nutrient DRs for this watershed. The models used 32 years of weather data from 1981 to 2012. The explanatory variables considered for the DR are distance to watershed outlet, flow, and pollutant loads leaving subbasins. They were chosen based on their strength of correlations and type of relationship with DR. Our results indicate that flow from each subbasin is the dominant factor affecting DR for this watershed. Together, the explanatory variables considered under the multiple linear regression framework were able to estimate sediment and nutrient DRs with satisfactory regression parameters. The R2 values for the regression relationship between the pollutant DRs and their counterparts estimated with multiple linear regression method were 0.8 for sediment, 0.96 for total nitrogen (N), and 0.9 for total phosphorus (P). The corresponding standard errors were 0.01 for sediment, 0.03 for total N, and 0.07 for total P. The explanatory variables were more strongly correlated to sediment DR than to nutrient DR. The tool developed to analyze changes in DRs for alternative scenarios appears to be useful for watershed managers.

Application of an environmental and economic modeling system for watershed assessments

Field-scale and watershed-scale environmental models are only capable of simulating mechanistically a limited number of practices individually. Furthermore, there is need for a mechanism to simulate environmental and economic models within a unified interface program in order to determine cost-effective practices. This study was conducted to develop an automated program, SWAPP (Soil and Water Assessment Tool (SWAT)-Agricultural Policy/Environmental eXtender (APEX) Interface Program), to convert SWAT files to-and-from APEX format and simulate SWAT and APEX simultaneously; integrate SWAPP and an economic model (Farm-level Economic Model; FEM); and evaluate the resulting program (Comprehensive Economic and Environmental Optimization Tool-SWAPP; CEEOT-SWAPP) using measured data.