Submitted to: International Safflower Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: May 5, 2001
Publication Date: N/A
Interpretive Summary: Safflower is an important oilseed crop in the Northern Great Plains region. Agronomists have shown by studying use of water and soil nitrogen from parts of soil profiles that safflower can extract these resources from deeper soil layers than can such small grain crops as wheat. We observed root growth and soil water use patterns of safflower to understand its agronomic potential. Root growth was observed and measured with a minirhizotron-microvideo system, in a miniature video camera is used to magnify images of roots growing up against walls of plastic tubes installed in the field. The average greatest safflower root growth depths observed with minirhizotrons in our glacial till soil during five years of study ranged from 5.0 to 5.8 feet. In comparison with other crop species, safflower rooted more deeply than pulse crops (dry bean, pea, soybean), mustards (canola, crambe), spring wheat and sunflower. Safflower water use e(soil water depletion plus seasonal precipitation) was greater than all other crops except sunflower, which consistently used more water than did safflower. Safflower is the most deeply rooted annual crop commonly grown in the Northern Great Plains, and further research on its belowground growth should be of interest to those studying carbon sequestration potentials.
Technical Abstract: Root growth of safflower was studied with a minirhizotron-microvideo system in two field studies conducted on Typic and Pachic Haploborolls. Root growth was measured for two years in a field study with three seeding date treatments. The average median depth (half of total root length above, half below) observed at root growth maximum was 1.02 m, and average maximum mdepth was 1.65 m. In a second field study, median and maximum root growth depths of safflower were found to be greater than those of seven other crops: dry bean; dry pea; soybean, canola, crambe, spring wheat, and sunflower. Average median depths at dates of greatest root growth for 1995, 1996, and 1997 were 1.09, 0.75, and 0.90 m, respectively; greatest maximum depths were 1.77, 1.52, and 1.64 m, respectively. Greater depth of rooting in 1995 is attributed to higher than average precipitation and consequently greater subsoil water content. Of the seven crops observed in nthe second study, only sunflower had higher water use during the 3 years than safflower. Measurements of water use in 10 crops during a third study confirmed that sunflower was the greatest water user, and that safflower was the second greatest, and both crops were shown to deplete from 3 cm to more than 10 cm of water greater an amount of water compared to other crops.