Cotton yields as influenced by ENSO at different planting dates and spatial aggregation levels

El Niño-Southern Oscillation (ENSO) is an important oceano-atmospheric phenomenon influencing crop production in the southeastern USA. Planting date is a major management variable that needs to be tailored to an anticipated ENSO event. Although ENSO effect may vary by planting date because crop season moves with planting date, no study has explored this effect for this region. Cotton (Gossypium hirsutum L.) production in Georgia is affected by ENSO, but no study has determined the ENSO effect at spatial scales smaller than a state. This study examined the ENSO effect on cotton yields in Georgia for various planting dates at three spatial levels: county, crop reporting district, and region. Using CROPGRO-Cotton, lint yields were simulated for 97 counties and 38-107. years, depending on county, each with nine planting dates within the planting window of April 10 through June 6. Yields were separated by ENSO phase, and tests were performed to find if yields were different across ENSO phases. Analyses at different levels showed different results regarding the ENSO effect. According to county level analyses, ENSO had little and spatially less consistent effect. The effect became more evident with a shift from smaller to larger level. According to regional level analysis, yield difference among ENSO phases was minimal for average planting dates, but substantial at the ends. For planting dates before May 9, yields during La Niña phases were higher than those during the other phases. For planting dates after May 23, however, yields during El Niño phases were higher.