Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2002
Publication Date: 12/15/2003
Citation: Purcell, L.C., Sinclair, T.R., Mcnew, R.W. 2003. Drought avoidance assessment for summer annual crops using long-term weather data. Agronomy Journal. 95:1566-1576. Interpretive Summary: Soybean yields vary considerably among locations and seasons. Much of this variation appears to be related to rainfall amounts during the growing season. In the southern regions of the United States, especially, the potential growing season is long and there may be opportunities to adjust the time when soybean is grown to avoid dry periods in the summer. This research, undertaken in cooperation with a USDA-ARS scientist located at Gainesville, FL, used a crop model that describes the basic processes of soybean development and growth to undertake this assessment. The analysis for the Midsouth confirmed a substantial advantage in drought-avoidance and yield by shifting the growing season from the summer to an earlier period. The analysis for the Southeast indicated that shifting the growing season from the summer to later in the season would be advantageous. No advantages were found in altering the growing season in the Midwest because of a relatively wet climate and a limited duration of the growing season.
Technical Abstract: The quantity and distribution of rainfall are key factors determining yield of nonirrigated, summer annual crops. Outside of the semi-arid tropics, however, systematic analyses of long-term weather data have not been used as a tool for directing breeding programs or for crop management options. We evaluated long-term weather data (ranging from 41 to 98 years) for 12 sites in three geographical regions of agricultural importance (Southeast, Midsouth, and Midwest) in the United States as a first step in drought-avoidance assessment. At the beginning of the growing season there was a period of approximately 62-d with P less than or equal to 0.20 of drought for the Midsouth, compared to a 48-d period for the Southeast. Towards the end of the growing season, there was an 62-d and 121-d period for the Midsouth and Southeast, respectively, in which P of drought was less than or equal to 0.20. For the Midwest, P of drought remained less than or equal to 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 found throughout much of the Midwest.