This study was conducted at the Pioneer Hi-Bred facility located in Woodland, California
(UTM Zone 10 coordinates: E: 600939, N: 4281280), which is the main summer location for
sunflower research. Summers are hot with an average temperature of 35.8o
C and winters are cold
with average minimum temperature of 3.1o
C. Precipitation occurs almost exclusively between
November and March, with an average of 470 mm per year (Western Regional Climate Center,
2011). The soil is classified as Yolo Silt Loam by the Soil Survey of Yolo County (Andrews,
1972). This soil is a member of the Fine-silty, mixed, superactive, nonacid, thermic Mollic