Dormancy Issues in Corn

Dormancy of a seed is controlled by pre-and post-maturation changes in the seed and changes that occur following harvest. The term, primary dormancy, is often used to describe dormancies induced by changes in the seed that occur before harvest. Secondary dormancy is used to describe dormancies induced following harvest by natural or artificial means.

When considering corn dormancy issues, the main concern is induced secondary dormancy. This type of dormancy will generally occur in corn and is often more prevalent in certain genetics and may last for several weeks after harvest. The dormancy is generally discovered during post harvest germination testing, specifically with the cold vigor test. Warm germination testing rarely shows any signs or symptoms of induced secondary dormancy and usually exhibits normal germination rates. However, cold tests may show very poor germination results and upon examination of the seed in the test, most seed appears completely healthy and firm.

When induced secondary dormancy is suspected in a seedlot, SGS Mid-West Seed Services recommends testing with a Tetrazolium (TZ) test to verify that the seed involved is, in fact, viable healthy seed. Confirmation that the seed is healthy then presents another option for testing with a Saturated Cold test. This test places the seed under a severe respiratory stress which will generally ‘break’ the dormancy causing the seed to germinate at normal rates. An additional option is to simply store the seed for 30 days or longer and perform another cold test. In most cases, the dormancy reduces over time and results from the cold test will improve considerably over earlier results.

Dormancy issues have increased over the past several years mainly due to the rapid turn around time required by most corn companies from harvest to conditioning and bagging. In the past, corn was generally put in the bin for at least 30 days prior to testing and, as a result, most dormancy issues were resolved prior to germination testing, see figure 1 below.