Drought Avoidance Assessment for Summer Annual Crops Using Long‐Term Weather Data

Abstract

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 <0°C was less than 0.05, water deficit was estimated as the difference between the 7‐d running sums of rainfall and potential evaporation. For comparative purposes across locations, a 7‐d water deficit >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.