We received numerous calls these past few weeks from Organic growers reporting poor stands of organic corn. These growers all planted their organic corn around the 15th of May.
On its face this is frustrating but not terribly surprising given the spring weather we’ve had this year.
Climate summaries from the University of Minnesota confirm what you all have experienced. Our May was cooler than normal (from 1˚- 4˚F cooler) with excessive rainfall in most of the state (we had over 4.3’’ at the seedhouse alone) and a lack of sunlight (over 75% of the days were cloudy). These cool, wet conditions are a perfect environment for fungal pathogens in the soil that kill seed & seedlings.
Fungal pathogens, like Pythium, Fusarium, and others, thrive in cool wet conditions where they infect the seed or seedling resulting in water-soaked discoloration of the mesocotyl and roots after emergence or rotting of the seed in the ground.
Not to mention, when soil temperatures are lower than 55˚F, corn emergence slows down greatly. The longer the seed sits in the ground the greater the chance of seedling diseases.
This results in what you experienced in the field, poor or uneven germination of your corn stands. These problems are further compounded under Organic management, as there is no approved seed coating currently that has efficacy on pythium & other root rots. Conventional corn is routinely treated with multiple fungicides, which allows conventional growers to plant early into unfavorable soil conditions and still get a descent stand.
We are constantly evaluating available OMRI-approved coatings & products to use on our Organic seed corn and we will continue to partner with innovative companies in the industry to find a coating that will provide maximum seedling protection for our organic growers.
In addition to fungal pathogens, we also had Organic growers report poor stands of corn following spring-terminated cover crops. Multiple producers who weren’t able to or didn’t terminate red clover in the fall of the year worked it up in the spring.
Seed corn maggots (among other pests that feed on corn seed) are favored by cover crops & cool, wet weather. These small larvae eat through the seed, meosocotyl & roots leading to poor germination & emergence. Damage to seedlings is most severe under spring conditions like we experienced this year.
We recommend growers work up plowdown cover crops (like red clover) at least two weeks prior to planting crops in the spring or working it up in the fall depending on the soil type.
This article was written by Matt Leavitt, Albert Lea Seed Agronomist.