To Coat or Not to Coat: That Is the Question

Debates about uncoated, light coated (9 percent) and heavy coated (34 percent) alfalfa seed are common among seed sellers and farmers. The skeptics argue there is less seed in a bag of coated seed, therefore you get less for your money. They may also claim that coated seed1 requires an increase in seeding rates to get the same stand. But research provides plenty of evidence that coated seed offers substantial benefits for an alfalfa crop. Here are five reasons why.

  1. Coated seed results in better stands. Critics of coated seed recommend increasing seeding rates because fewer seeds are planted per square foot. They debate the pure live seed (PLS) concept, attempting to illustrate coated seed is worth less per pound. However, farmers need to understand that coated seed changes the PLS paradigm. Coated seed has a higher seed-to-seedling success rate than uncoated seed. Therefore, fewer seeds produce a similar stand.

Research by Purdue University showed that coated seed produced as many seedlings per square foot as uncoated seed (29.5 and 30, respectively) when 21.8 pounds of alfalfa seed was planted per acre (uncoated = 78 PLS/ft2 and coated = 56 PLS/ft2). They also planted at 14.5 pounds per acre (uncoated = 52 PLS/ft2 and coated = 38 PLS/ft2) and ended up with similar stand counts for each: 31 and 29 seedlings/ft2, respectively.2

  1. Coated seed offers better seed-to-soil contact. Larger farms and bigger farm equipment mean a reduced amount of time spent preparing seedbeds, resulting in seed placement that is less than ideal with poor seed-to-soil contact. Coated seed offers better moisture absorption and transfer to the seed for germination. The coating material (often lime) attracts water better than the seed itself. This was verified by lab research where coated seed had about a 12 percent better germination rate than uncoated seed from the same seed lot.3


  1. Coated seed provides greater protection against early-season pests. To verify, two sets of three seed treatments (uncoated, 9 percent coated and 34 percent coated) were sampled and chemically analyzed for the fungicide active ingredient mefenoxam. In both cases, the rate of fungicide per seed was highest on the 34 percent coated seed and lowest on the uncoated seed. This makes sense, given that dose recommendations for alfalfa are based on weight, not seeds per pound.3