Normally a dry fall is great for soybean seed producers because it lowers the levels of seed infection, increasing both seed germination and seed vigor. Last fall, however, the dry weather was too much of a good thing. Soybean seed dried so quickly in many fields that moistures were well below the ideal seed moisture for harvest of 13 to 14 %. Seed moistures of 9, 8, 7 % or lower were not uncommon. These low moistures make the seed very brittle and easily damaged during harvest and seed handling after harvest.
Some of this damage was obvious, increased splits and large cracks in the seed coat, but much of the damage was hard to see. The latter included small cracks in the seed coat, cracked cotyledons, and damage to the seed embryo. There may also have been damage to cell membranes. These injuries can lower seed vigor (measured by accelerated aging tests), seed germination (measured by standard germ tests) or both.
Damage to seed coats can also increase leakage of nutrients from the seed, which after planting, may further lower seed vigor and increase disease pressure from soilborne pathogens. Damaged seed may not store as well, losing vigor more rapidly than undamaged seed. This could be a problem with late plantings (after June 1st) where stressful planting conditions like high soil temperatures, low soil moisture, etc are encountered and lower seed vigor could lead to stand failure. Given the current wet conditions in much of eastern Arkansas which is delaying planting, this is a cause for increased concern about seed quality.
• Talk to your seed dealer about germ and accelerated aging (vigor) results for each seed lot.
• Request accelerated aging (AA) information for seed lots to be used for June-July planting
• Recent accelerated aging (AA) results within 60 days of planting are suggested based on recent observations
• If AA results cannot be obtained from dealers, you can collect and send your own sample to the Arkansas State Plant Board for a small fee. Samples have to be collected, handled and shipped properly to provide accurate results, and you must allow adequate time for tests to be performed (at least two weeks). So now is the time to consider testing, if needed.
• Contact the Arkansas State Plant Board at 501-225-1598, 1 Natural Resource Drive, Little Rock, AR 72205 for additional information on seed sampling and testing.
• If you suspect a problem, consider increasing planting rates (based on recent seed quality testing) and applying a recommended fungicide/insecticide seed treatment to protect against soilborne pathogens and insects during germination and emergence.
• Extreme care in handling and treating seed this year is warranted to avoid further mechanical damage to seed coats.
• Extra care should also be taken to prepare the seedbed, avoid compaction, set planting depth properly, and better monitor soil moisture at planting to assure the best chance for germination and emergence.
• Seed supplies of many popular varieties are tight again this year, therefore growers must strive to get a stand the first time.
Additional authors include:
Mary Smith, Arkansas State Plant Board
Jeremy Ross, Cooperative Extension Service, University of Arkansas Division of Agriculture
Lanny Ashlock, University of Arkansas Division of Agriculture