Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: October 26, 1997
Publication Date: N/A
Technical Abstract: In the SE USA Coastal Plain, intense variation in soils causes intense variation in crop yield. Of common field crops, corn (Zea mays) appears to be the most susceptible to soil variation, especially during drought. A severe regional drought in 1993 provided a unique opportunity to observe possible causes of yield variation. We measured site-specific effects of soil variation on crop water relations. Soil moisture was measured using time-domain reflectometry, and drought stress was measured using IRT canopy temperature (Tc). During the drought, visibly stressed areas had canopy-air temperature differences (Tc-Ta) above 10 degrees C; other areas were below 2 degrees C. A 46-mm rain reduced Tc-Ta to near zero for all soils, indicating that most stress was relieved. Water balance results were dominated by site differences in runoff and evapotranspiration. Patterns of water stress matched those inferred from yield components. These results showed that the eight sites arrived at final yields via radically different ways.