VOLUME 3 ISSUE 4 WINTER 1993

SURE FIRE SWITCH

The following information is provided as a result of research done by Dr. Dale Wolf and Dave Parrish, Research Agronomists, Virginia Polytechnic Institute and State University, 1991. Used by permission.
Dormancy presents a problem for quick establishment of switchgrass in field conditions. Cave-in-Rock switchgrass is notorious for dormancy. One way to deal with this problem is to plant year old seed. However year old Cave-in-Rock is difficult to come by. Demand for switchgrass seed has kept up with supply, as a result most producers are not able to store Cave-in-Rock seed for a year before selling it. Many producers choose to plant other varieties, such as Blackwell, to avoid this problem. The trouble with substituting varieties is the substituted variety may not be the best adapted to the intended use or geographic region.

This creates a real dilemma for the producer; use a less than desirable variety or gamble on the establishment time of Cave-in-Rock with high dormancy. Dr. Wolf and his colleagues have developed a way to enhance the establishment time of switchgrass seed with high dormancy. The first step in the process is to determine if the lot of seed you have has a dormancy problem. Not all seed tags will report dormancy in a manner which will be easily understood. In addition different states have different regulations on how seed dormancy should be reported, if at all.

To check your lot of switchgrass seed for dormancy you need to conduct a "ragdoll" test. Remember your science class in school when you wet a brown paper towel, put some beans in it, rolled it up then a few days later unrolled it to see the sprouted beans? That's a "rag doll" test. Dr. Wolf suggests, "Use a firm paper towel such as a brown hand towel or equivalent. The "soft" very absorbent paper toweling often used in a kitchen makes poor rag dolls. Cheap paper towels for the kitchen can be used but it is best to use 2 layers. These towels carry too much water so squeeze some water out before use."

Wolf and Parrish continue with the following instructions, "Wet the towel and allow free water to drip off for a minute. Lay the towel flat. Count out 100 seeds and place them on one half of the towel. Fold the towel in half and roll it into a moderately tight tube. Rolling it around a pencil works well. Place the tube in a jar or plastic bag. Position the rag doll so the tube is upright. Doing this causes roots to grow down and shoots to grow up so that seedlings are more easily removed during counting. The rag doll should be kept in a warm place. A little water in the bottom of the jar or plastic bag will insure adequate moisture.

For many crops, about 80 to 85 degrees F is best but just room temperature is OK. If held at room temperature, make your first count for most crops in about 3 to 4 days. Open the towel and count the seedlings as you remove them. After another 3 to 4 days make a second count. If you had 100 seeds, the number of seedlings removed equals the percentage germination."

The next step is to compare the results of your germination test to that listed on the seed tag. If the germ listed on the seed tag is significantly higher than your results, that indicates dormancy in your seed.

If dormancy exists in your seed you have a couple of options. One option is to plant your switchgrass early. Dr. Wolf suggests 2 to 4 weeks before typical first date for planting corn. It has been my experience that a dormant season seeding, late fall through winter or a frost seeding will also help to break the dormancy.

The second option, as recommended by Dr. Wolf, is a wet-chill pretreatment followed by drying. "Place about 40 pounds of seed in a cloth bag and submerge in water for about 12 hours. Hang the bag so that water can drain freely for about 1 hour. Placing seed on a tray (about 2 inches deep) is ideal since seed needs oxygen.

If placed in a plastic bag, lay the bag flat so seed is no more than 2 inches thick. Don't allow seed to dry excessively. Stir each 2 - 3 days to keep oxygen from being limited. Place the seed where the temperature will be between 40 and 50 F. Hold the wet seed in the cold for about 14 days. After the chilling treatment, spread the seed in a thin layer on a hard surface, tarpaulin, or plastic sheeting. Use a fan to circulate air so seed will dry quickly as possible. Stir the seed with a broom or shovel to help uniform drying. Keep the seed out of the sun so they don't heat and begin germinating. When the seeds seem dry, they can be put in a cloth bag. Plant as soon as possible. It is a good idea to check the seed using a rag doll test to see if germination was improved. Always keep a small sample of seed so that further testing can be done if stands are no good."

I will offer one strong caution here. Once the seed has been treated and readied for planting, plant as soon as possible. On one occasion I shipped wet-chill treated eastern gamagrass seed which got hung up in shipping and when it arrived, the seed had sprouted in the bag. I have also noted on a couple of occasions that after seed had been dried, if not planted, not only had the dormancy returned but was higher than initially.

In a field trial to test the wet-chill pretreatment, untreated seedling population was approximately 1 plant per square foot compared to treated seed which was approximately 36 plants per square foot. Seed was harvested in 1990 and planted June 15, 1991.