Lorne Klein, PAg
Regional Forage Specialist, Weyburn
Saskatchewan Ministry of Agriculture
When seeding perennial forages, there is a common understanding that 10 lbs/ac is the standard correct seeding rate. Not necessarily. A sufficient seeding rate for a seed mix depends upon the plant species you have chosen and the amount of each you include in the mix. Ultimately you want to know the number of seeds per square foot of each species you are applying.
According to CFIA regulation, plant species in a forage seed mixture are listed as “percentage by weight”. This is necessary to maintain consistency across the industry. However, the percentage by weight is not representative of the seed counts.
The approximate number of seeds/lb varies significantly from one species to another. A chart in the Ministry of Agriculture Forage Crop Production Guide lists the approximate number of seeds/lb of each of the forage species. The seed counts are based on bare, uncoated seed.
Comparing legumes, sainfoin has 30,000 seeds/lb and uncoated alfalfa has 200,000 seeds/lb. Comparing uncoated grasses, hybrid brome has 90,900 seeds/lb and crested wheatgrass (diploid) has 220,000 seeds/lb.
A seed mix including 30% alfalfa, 20% sainfoin and 50% hybrid bromegrass by weight would contain about 111,450 seeds/lb. For each pound per acre applied, you would be seeding about 2.6 seeds/ft². A seed mix including 10% alfalfa, 40% sainfoin and 50% hybrid bromegrass by weight would contain about 77,450 seeds/lb. For each pound per acre applied, you would be seeding about 1.8 seeds/ft².
When over seeding across periodic wetland and riparian areas, a combination including 50% alsike clover and 50% reed canary by weight would be an option. This seed mixture would have about 937,500 seeds/lb. For each pound per acre applied, you would be seeding about 21.5 seeds/ft².
The calculations above are based on bare seed. Ask your seed supplier if some or all of the seeds in your mix are coated, and the amount of coating. Typical coatings can reduce seed counts by 35% for alfalfa and 50% for grass.
The target number of seeds to apply per square foot varies across soil zones. Generally the range is from 20 seeds/ft² in the Brown Soil Zone to 30 seeds/ft² in the Black Soil Zone. These rates tend to be on the higher end of the scale. Rates 25-50% lower can be used if you are confident that your agronomic practices and establishment conditions result in a high percent of plants establishing. Seeding rhizomatous species such as cicer milkvetch, hybrid brome and smooth brome enable lower seeding rates as these species have the ability to spread and fill in a stand over time.
Adding to the seed mix decision is the amount of each species you are targeting for the stand, both in the short and long term. A seed mix with 10 seeds/ft² of both alfalfa and meadow bromegrass will normally be dominated by alfalfa for the first 3-4 years. As the stand gets older, depending upon fertility and haying or grazing management, the normal progression is that the alfalfa declines and the grass becomes more dominant. For fields you intend to bale in the early years and graze in later years, you will want to start with a high percentage alfalfa stand, so you have sufficient alfalfa plants as the stand gets older.
Perennial forages are seeded only once every 5-55 years. Take the time to plan your seed mix and increase the chance of getting the stand you are targeting. For more information on seeding rates for seed mixtures, contact me at 306-848-2382, or call the Agriculture Knowledge Centre at 1-866-457-2377, or visit our website at www.saskatchewan.ca.
