Spatial Quantification of the Gap between Farm Field and University Trial Maize Yields in the United States

Abstract

Greater crop production will be required to support both an increase in biofuel use and a forecasted doubling of global food demand by 2050. An improved understanding of yield potential and realistic estimates of the magnitude and spatial variability of the gap between actual yield and yield potentials are critical to achieving maximum crop production. This study examines near-term yield potentials and gaps of maize (Zea mays L.) yield data over the years of 2006 to 2011 from two sources: university crop variety trials and the United States Department of Agriculture yield surveys. Yield potentials are analyzed across 32 states through a compiled database of 129,499 trial maize hybrid entries. From the database, 1,102 direct, irrigation-specific, year-to-year, county-to-county yield comparisons are made across 27 states. These 32 and 27 states comprise nearly all United States maize production—99% and 97%, respectively. Trial yield is calculated as the 90th percentile of hybrid yields in a given county in a given year, and farm yield is the USDA-reported county-level yield in that same trial-performing county in that same year. Analysis of the median yield gap values in each state shows a yield gap of 13% to 53% in rainfed maize and a yield gap of 16% to 39% in irrigated maize. The magnitude of these differences between farming and trial yields indicates that maize yields in the United States, particularly rainfed, have considerable room for improvement. Additionally, the 40% range of median rainfed yield gap values and the 23% range of median irrigated yield gap values suggest that the yield gap varies greatly between states. The results of this study are expected to support the production of more accurate biofuel crop projections and identify where yields might be increased, thereby avoiding further land conversion to cropland while reaching the goal of increasing biofuel production and sustaining ample food production.