Calculating Agricultural Productivity In Select Virginia Counties.

Assessing agricultural productivity is an important aspect of land use and land change. This theme emerges in studies of local and regional food security, climate change, bioenergy production, and land change impacts on ecosystem services. We assessed agricultural productivity by linking the Soil Survey Geographic database (SSURGO), with Virginia Agricultural Land Use Evaluation System (VALUES), a field verified database linking realistic crop yields to agricultural soil series in Virginia. The study included four counties which were identified as fully urbanized (Chesterfield), rapidly urbanizing (Henrico), rural with significant land change (Ablemarle), and rural with little land change (Charles City). The initial linkage of SSURGO and VALUES included large areas of non-productive and non-agricultural land. A series of corrections improved identification of agricultural areas in each county. These included slope based exclusions and yield reductions, and exclusion of non-agricultural polygons based on filters and combinations of change layers from NASS CDL, and NLCD, and cadastre layers for these counties. The refined productivity map and population data were used to calculate a county Food Energy:Population ratio, which is potential calories produced divided by calories required by the current population. Assuming corn was grown on all agricultural land, and each person requires 2,300 kcal per day, the calculated food energy ratios (and population) were: Ablemarle 14.4 (94,075), Charles City 44.9 (7,212), Chesterfield 0.44 (303,469), and Henrico 1.05 (292,599). Agricultural land currently represents 24%, 18%, 4% and 13% of the respective county's area. We anticipate use of these tools in planning, foodshed, and bioenergy assessments.