Agronomic Factors Affecting Grain Sorghum Maturity In Northeastern Colorado.

Grain sorghum is an important dryland crop in eastern Colorado, but it is produced on few acres in northeastern part of the state due to the relatively short growing season and the challenge of ensuring that it makes it to physiological maturity before the first fall frost.  Being able to produce sorghum in this region would give farmers another option for a spring crop to use in their wheat rotations along with corn and proso millet.  In 2010, a study was conducted at two locations in the region to compare the effects of using different hybrids and agronomic treatments to get sorghum to physiological maturity.  The study investigated different agronomic factors such as row direction, seeding rate, and row spacing, along with hybrid selection within the early to medium-early maturity classes.

Preliminary results show that planting rate and hybrid treatments have a substantial impact on the amount of thermal time it takes for the sorghum to reach physiological maturity.  In the first year of the study, the hybrid selection had the most significant effect on the thermal time to maturity across the two locations. There were also substantial maturity differences noted between hybrids within the same maturity class. The study is being repeated in 2011 at two additional locations within the region and the results are expected to support our preliminary results from the first year.