A couple of Michigan State University agronomists are reminding corn and soybean producers to keep a close eye on both soil temperatures and the near-term weather forecast when planting this spring.
Writing on the university’s IPM web site, Bruce McKellar and Mike Staton say that cold conditions at or immediately following planting can be detrimental to early development.
Staton mentions a trial by in Ontario by OMAF soybean specialist Horst Bohner that showed how soybean germination and emergence varies depending on the temperature of the first soil moisture taken up. Bohner compared three scenarios: soybeans exposed to warm conditions (77F) for 17 days, old soils (45F) for 20 hours followed by warm soil for 17 days, and eight hours of warm soil followed by a four-day cold spell.
The results showed that soybean seedling vigor, growth and development were greatly impacted when the temperature of the soil moisture first taken up by the seed was cold as compared to seeds that were exposed to warm soil and warm soil followed by cold conditions.
Staton stresses that the temperature of the soil moisture that first hits the seed is important. Overly dry seed and seed with thin or split seed coats is more susceptible to imbibitional injury. Soybean producers should know the quality of each seed lot and plant the highest quality seed first and the poorest quality seed last
The situation is not much different for corn. Purdue University corn researcher Bob Nielsen has found that soil temperatures below 50 F can be risky for corn seedlings. Estimates of the critical soil temperature for corn vary, with some sources saying 50F and others putting the threshold closer to 41F.
Injury occurs when the cell tissues of the kernel are too cold; tissues become less elastic and may rupture during the seed swelling process. Damage usually occurs during the initial 24 to 36 hours after planting under normal soil moisture conditions. Symptoms include failure to germinate, slow development of root and coleoptile growth following initial germination, McKellar explains.
To reduce risk from chilling injury, growers should look at the soil temperatures at the time of planting in combination with a favourable two to three-day temperature forecast. With adequate soil moisture, the first 24 to 36 hours may be the most critical to help prevent chilling injury from occurring to the developing seedling, the researchers say.