Development of a Regional Aggregated Crop Yield Index.

The capacity for food production at the regional level under climate change depends on the natural resources base, and on the management and physical inputs available to farmers.  In the Northeast U.S. (12 states, from West Virginia to Maine), more than 200 crops are grown, but yield and land area estimates are available for only a few.  Our objective was to use long-term, county-level data from the region to 1) assess the potential for development of a multi-crop yield index, and 2) establish temporal and spatial trends for crops yields that could be incorporated in projections of productive capacit under climate change.  County-level yield estimates were obtained for the period 1981-2010, from the USDA-National Agricultural Statistics Service (NASS) annual survey, for corn (Zea maize L.), wheat (Triticum aestivum L.,) and potato (Solanum tuberosum L.), soybean [Glycine max (L.) Merr.], and perennial hay (across categories). The correlation between yields of these crops was low (r < 0.20), suggesting that they are not grown on the same land base, which was supported using spatial data on crop distribution.  The regional mean yield of corn and wheat exhibit clear trends for increased yield, allowing us to estimate temporal trends; this was not the case for potato or hay.  Results will also be presented on normalized crop yields, defined as the ratio of county-level yield to regional yield for each year, which was used to assess spatial trends in productivity, to identify clusters of high- or low-yielding counties.