« Back to Resource Library

Stone prepared this report in October 2015 for the Vermont Natural Resources Conservation Service and Vermont Agency of Food and Markets.

Excerpt from the Report (Introduction):

This report documents the development and evaluation of a web-based APEX model simulation tool, Vermont Systematic Tool for Analyzing Resources (VT STAR), designed for the Vermont Natural Resources Conservation Service (NRCS). The VT STAR tool was developed to design conservation plans for Vermont farms using the United States Department of Agriculture’s (USDA’s) latest agricultural water quality modeling technology (APEX) and farm field specific topography, soil, weather, and agronomic management data sources. The tool was designed such that comparisons of multiple conservation management alternatives can be evaluated as part of a single conservation planning assessment in order to efficiently arrive at the best management practice choices for a specific field and farm. While VT STAR was targeted for use by NRCS conservation planners, the tool will be of value to additional Vermont stakeholders concerned with water quality and the optimal implementation of agricultural best management practices throughout the state. 

The first section of this report describes the datasets that have been compiled for use in VT STAR and for populating the APEX model simulations generated for each assessment. This is followed in Section 2.2 by an overview of the VT STAR application development components that were implemented to meet the needs requirements for STAR use in Vermont. The testing and evaluation of VT STAR is covered in Section 3 and focuses on the APEX model simulation results over a range of crop management systems and field conditions. The objective of the testing and evaluation was to assess whether the results generated by APEX and reported in VT STAR fell within expectations based on our conceptual understanding of agricultural water quality in Vermont. The evaluation included both a relative comparison of multiple fields with and without conservation practices under similar cropping systems, as well as a comparison of STAR-predicted results with site specific edge-of-field monitoring data. Overall, the testing and evaluation of VT STAR provided increased confidence in the model predictions. The relative comparisons of sediment and nutrient load predictions followed the expected trends across the different fields and practices, and the comparisons of the model predictions with the monitoring data were reasonable. As the use and testing of VT STAR continues, it is quite possible that additional adjustments to the parameterization of some types of management schedules and conservation practices will occur. In the meantime, the conservation planning assessment data being generated by VT STAR has been found to be representative of a broad range of conditions important to Vermont agriculture.

Both the VT STAR Training Exercise Workbook and the VT STAR Application manual are included as appendices in this report. The training exercise workbook was used for VT STAR training that was conducted at the VT NRCS office on September 15th, 2015. This workbook guides new STAR users through the critical steps required when conducting a conservation planning assessment. It includes clear examples that provide users with a strong foundation for using VT STAR. The VT STAR Application Manual provides additional documentation of VT STAR features and functionality that were not touched upon in the Exercise Workbook.