Severity, Extent and Persistence of Spatial Yield Variation in Production Fields in the SE US Coastal Plain

Abstract

In the US SE Coastal Plain, adoption of site-specific farming has lagged behind that in the upper Midwest. While reasons for this may be both social and economic, it appears that the importance of the problem represented by yield variation on production fields needs to be quantified before adoption would be considered by many farm operators. Our objective was to document the severity, extent and persistence of yield variation for corn, wheat and soybean during normal production in this region. Farmer combines were fitted with commercial yield monitors to produce yield maps. Corn, wheat and soybean yields were mapped for three years on more than 4900 ha (12,000 acres). For each cooperator, crop and year, summary statistics and cumulative yield distribution functions were also developed. Yield maps showed that substantial areas had yields either well below or above the mean for the cooperator-crop-year. For instance, 25% of Cooperator A’s area had corn yields more than 30% below the mean yield of 5.06 Mg/ha and another 25% had yields more than 31% above that mean, which indicate the severity of yield variation. Variation from county to county had no consistent difference indicating that the extent of the variation is widespread. Variation was also persistent from year to year, with more than 50% of the area in 15 of 17 fields having stable yields relative to the field mean. These data show the potential importance of variable-rate management in the region and also hint at the potential environmental implications.