Drought avoidance assessment for summer annual crops using long-term weather data

Seasonal rainfall is a key factor determining yield of nonirrigated, summer crops. In temperate regions, however, systematic analyses of long-term weather data have not been used for directing breeding programs or for crop management options. We evaluated long-term weather data (36-98 yr) for 16 sites in four geographical regions in the USA to assess the potential for drought avoidance. For each day of year when the probability (P) of having a minimum temperature 50 mm was defined as a drought. For the Midsouth, there were approximately 62 d at both the beginning and end of the growing season with P ≤ 0.20 of drought. In the Southeast, there were approximately 48 d and 121 d at the beginning and end of the growing season, respectively, with P ≤ 0.20 of drought. For the Midwest, P of drought was ≤0.20 throughout the growing season for three of the four sites, and it was concluded that a 50-mm water deficit was not likely to be a production constraint on the deep soils of the Midwest. For the Northern Great Plains, P of drought was >0.20 for more than half of the region's growing season. This meteorological approach for assessing drought may provide insights for drought avoidance in breeding and crop management.