Source: Saskatchewan Agriculture and Food
It has long been recognized that uniform seeding emergence is critical to stand establishment and production in forage crops, but a lack of comparative data between what happens in the lab and in the field made seeding practices more of a trial and error process, until now.
A recent Agriculture Development Fund (ADF) supported research project, conducted by the University of Saskatchewan, has shed new light on this issue, through dormancy modeling.
Dr. Yuguang Bai of the Department of Plant Sciences was the lead investigator on the project, with Doctors Bruce Coulman and Jim Romo as co-investigators. Mr. Jie Qiu, currently a Ph.D. candidate at the department, formed his M.Sc. thesis based on this project.
“We observed that for forage species, when addressing the issue of seed dormancy, often there is a disagreement between seed germination tests in the laboratory and seedling emergence in the field,” Dr. Bai said. “We wanted to find out the reason for the difference, and we hoped the results would help producers in selecting the optimal seeding rates as well as the best seeding dates.”
Field experiments were conducted near Saskatoon in 2003 and 2004 using two cultivars of western wheatgrass and orchard grass, with four seeding dates ranging from early May to mid-June. Laboratory experiments were conducted to determine the effects of temperature on seed dormancy and the prediction of seedling emergence using the thermal time model.
“It seems that the fluctuating temperature in the field is a critical element that affects seed dormancy and germination,” according to Dr. Bai. “Using a thermal time model approach, we discovered that temperature does indeed affect dormancy, and that fluctuating temperatures can break dormancy in the two species studied under field conditions.”
Dr. Bai explains that a 10 degree Celsius difference between high and low temperatures was most efficient in dormancy breaking, which was close to temperature fluctuations measured in the field at a 1 cm seeding depth.
“The implication is that if you want to test germination for the determination of seeding rate, you need to mimic temperature conditions in the field. Otherwise, if you use constant temperatures for germination tests, you will end up with unnecessarily high seeding rates,” said Dr. Bai.
“Between orchard grass and western wheatgrass, the western wheatgrass has a narrower range of optimal temperature for germination and dormancy breaking.”
As a result of his research, Dr. Bai believes a later seeding date of late May or early June would result in the best seed germination, seedling emergence and stand establishment for western wheatgrass when soil moisture is not limiting.
“Orchard grass, on the other hand, is less sensitive to temperature during dormancy breaking and germination. Thus, seeding between early May and early June would yield good results, and seedling emergence in the field can be predicted with the thermal time model.”
A copy of the Final Report titled “Enhancing Seedling Emergence and Productivity of Forage Grasses Through the Modeling of Seed Dormancy Change” (ADF #20020016) may be obtained by phoning (306) 787-5929 in Regina. The final report is also available on the Saskatchewan Agriculture and Food website at www.agr.gov.sk.ca.
For more information, contact:
Dr. Yuguang Bai
Department of Plant Sciences
University of Saskatchewan
(306) 966-4955
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