By Sjoerd Willem Duiker
Cover crops are becoming very popular to improve soil health and supply other services such as improve water infiltration, reduce phosphorus runoff and soil nitrate leaching, and provide grazing or harvested forage. Demand for cover crop seed is therefore on the rise. Farmers have different options – the most secure method is to buy cover crop seed from a seed company. Companies provide assurance of the variety you use and publish purity and germination on the seed label. However, some farmers choose to use bin-run seed from their own or from a neighbor’s farm.
If you use bin-run seed, you should do a germination test and correct for purity and germination. To determine purity, take a scoop of dry seed, weigh it using a kitchen scale, and then weigh it after you remove all foreign materials (weeds seeds, dirt, crop residue). Express purity as a % of the initial weight. Determine germination rate by taking a representative sample of seed from your lot and counting out 25-100 seeds. Include broken or shriveled seeds as they are also part of your lot. Take a paper towel, fold it in four, moisten it thoroughly and place it in the bottom of a plate. Put the seeds on top and place the plate in a zip-lock bag at room temperature. After about three days check the plate and tip it to remove excess water without opening the zip-lock bag (to maintain 100% humidity inside). After 8-10 days you count the germinated seeds and express them as a percentage of the total. To determine seeding rate you should divide the desired seeding rate by the % pure live seed to get the needed seed per acre. Pure live seed is the product of purity x germination. So if you have 90% purity (10% of the weight is foreign material or weed seeds), and 60% germination, your PLS = 0.90 x 0.60 = 0.54 = 54%. If the desired seeding rate of live seed is 100 lbs/A, you should plant 100/0.54 = 185 lbs/A.
Although some of the seed may carry scab disease this is not likely to cause scab in the following crop, so actually, planting poor quality seed may be a good use of bin-run low quality seed as long as you correct for poor germination. While bin-run seed can be used on your own farm without a problem, you have to make sure you follow the laws of Pennsylvania regarding seed sales. If you sell seed to another person you become a seed distributor and you need to apply for a seed license, the cost of which is $25 per calendar year. In addition, you need to get a germination/purity test done by a seed lab. The Pennsylvania Department of Agriculture can do that for you for a $32 fee. You have to properly label the seed that you sell.