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Soybean seed moisture levels

Higher levels reduce dehydration and chilling injuries, boosting germination and vigour. 

The early stages of germination are a critical time for a soybean seed.  A seed’s performance is strongly affected by its starting moisture content, before it is even planted. Seeds that are too dry at planting are more susceptible to chilling and dehydration injuries, which result in decreased germination, slower growth rates and generally lower seedling vigour.However, how exactly seed

Josh Segeren travelled to Atlanta in May 2008 to present the findings of his research on seed moisture levels to the Intel International Science and Engineering Fair.Photo courtesy of Josh Segeren. Advertisement

moisture relates to field performance is a question that has not been closely studied, until now. From February 2007 to February 2008, Josh Segeren undertook research to determine this, and in May 2008, Segeren, a grade 11 student at John McGregor Secondary School in Chatham Ont., presented his results at the Intel International Science and Engineering Fair (IISEF), held in Atlanta. With more than 1500 of the world’s most promising young scientists in attendance, it is the largest competition of its kind.Segeren says the research stemmed from his previous studies on the best time of day to plant soybean seeds.  “After that research, I was left with several unanswered questions,” he says.  “I realized that injuries during soil water absorption (imbibition) such as chilling and dehydration are significant and prevalent. Surprisingly, many of the current techniques used to counter these injuries are relatively expensive and cannot be practically integrated. Research into seed moisture levels as they relate to attaining maximum yields is certainly of interest in these times of high input costs.”

Experiment details
Josh tested seeds at eight, 10, 12 and 14 percent moisture under both lab and field conditions.  “My results recommend that producers should aim for a soybean harvest moisture between 12 and 14 percent,” he says,  “although subsequent drying to these percentages at a low heat setting with sufficient air circulation is also an option.”

He adds  “Regulation of soybean seed moisture content at 12 to 14 percent during harvest and storage would be a low-cost and easily integrated solution to increase yield, and therefore ultimately the world food supply.” He states that this can be accomplished by ensuring that contract growers are aware of these findings and to be as strict as possible during harvest to meet these recommended levels.  “Furthermore, these moisture contents could be maintained during storage through consistent and monitored temperature and humidity levels,” he notes.

Segeren also found that if seeds are dried below 10 percent moisture, their viability after planting is greatly inhibited. Soil moisture is absorbed very quickly, and as it proceeds the seed must make a transition from its dry, dormant state to a biologically active growing state.  Overly dry seeds are slower at making this transition, which causes a cellular activity spike, wastefully burning up the seed’s energy reserves and damages the cell membrane. The overall result is lower vigour embryos and poor germination rates.

Among others, Dr. Hugh Earl, an associate professor in the Department of Plant Agriculture at the University of Guelph, provided guidance and support to Segeren. Regarding the research findings and their significance, Earl says  “The most surprising thing to me was the very large and statistically significant effect of initial seed moisture on final crop yield. That result shows that there is something important going on here, not just in a laboratory context, where we have been studying these things for decades, but in the field, where it matters.”

Earl adds, “What Josh has produced here is one of the best demonstrations I know of, to date, of the potential effects of soybean seed quality, in terms moisture content, on emergence, vigour, and ultimately yield of the crop under Ontario growing conditions. This is particularly important now when many growers are looking to cut back on seeding rates to increase profit margins. Anything that can increase emergence and vigour of those fewer seeds going into the ground enhances the bottom line.”

Reflections on the research

Overall, Segeren is pleased with his project’s performance. “I feel good about it being one of the 16 Canadian projects selected for Team Canada competing at the IISEF,” he says. “The rules were very strict, and each project had to pass multiple inspections regarding both safety and scientific legitimacy of the work. Research plans had to be submitted and reviewed before conducting experimentation, and after project reports were submitted, there were interviews.” The most difficult aspect of the project, says Segeren, “was likely designing a procedure to simulate the different conditions for the first phase of experimentation, as well as overcoming the limitations of conducting the experiments entirely at home and at the field level.” He won fourth place, and an award of $500 in the Plant Sciences category. The competition aspect aside, Segeren says “This project means a great deal to me, since I am able to see the results of my work within my community. This project has taken me many places and offered many exciting opportunities. Because of it, I have had the pleasure of meeting like-minded, ambitious people from all over the world, which has been a tremendous source of inspiration.” Segeren was struck by the energy, enthusiasm and intellect displayed by participants.

“Everyone there was equally passionate about their work, with good reason,” he says. “I realized that I was likely amidst the future leaders of this planet.” Segeren notes “I was very fortunate to have been referred to Dr. Earl, who played an extremely valuable and supportive role, and, in many ways, went above and beyond all expectations.” For other important guidance and support, Josh thanks his parents, farmers Gary and Michelle, Mary Ellen VanZelst, a seed lab manager with Pioneer Hi-Bred Limited in Chatham where Gary works as a production technician, and Phil Snider, science department head at his school.Earl was glad to be involved: “I can’t even describe how incredibly heartening it is to me to see such a promising young scientist applying his considerable talents so enthusiastically to the field of agronomy.”

He is also quick to point out that the project was completely Josh’s. “I want to be clear that everything he did, he truly understood from first principles,” says Earl. “I never took his data and did the analysis for him. In one e-mail exchange, I explained to him how to do linear regression analyses manually, and how to interpret the results so as to determine the level of statistical significance of his various findings. He did it first try. He was in the ninth grade, I think. This is something we teach to second year undergraduates, and many of them struggle with it.”

Segeren describes himself as relatively undecided about his long-term career plans: “Currently, I plan to obtain degrees in both Science and Business Administration and further my studies in graduate school.”

Earl concludes, “Josh clearly has a passion for crop production and for the underlying basic sciences. I would certainly love to see him carry those interests forward, but if he chooses another direction entirely I have no doubt that he will excel and make very significant contributions. He’s a pretty special young man.”