Producers took many approaches to dealing with fields they couldn’t plant in 2019, from letting weeds grow to tilling them and leaving them bare to planting cover crops. If you have prevented planting fields, here’s a little-known phenomenon worth addressing. It’s called “fallow syndrome.” Simply put, the crop planted a year after a field is fallow may get off to a rough start, particularly if it’s corn.

Why does fallow syndrome occur? Mike Riffle, product development manager for Valent USA MycoApply brands, says the decrease in active mycorrhizal fungi, beneficial fungi naturally found in the soil, is one possible cause. When a field is left fallow, mycorrhizal fungi don’t have host plants available, which decreases their survival. This can lead to fallow syndrome, because these beneficial fungi aren’t available in the soil to support plant roots in the acquisition of nutrients, especially phosphorus, and water.

Betsy Bower, an agronomist with Ceres Solutions LLC based in west-central Indiana, adds that grass crops such as wheat, corn and grain sorghum are particularly susceptible. Grass crops leak sugars from roots that support the mycorrhizae fungi and the mycorrhizae fungi assist roots in taking up nutrients, primarily phosphorus and zinc.

Here are four ways Bower says you can avoid impacts from this syndrome:

1. Plant a cover crop. You still can plant rye or wheat cover into November, December or early January if planting conditions allow. If it’s your first cover crop, consider terminating it early in the spring ahead of corn when rye is 8 inches tall or less. 

2. Band starter phosphorus and zinc. Consider phosphorus and zinc in corn, preferably as pop-up starter, or in two-by-two placement or both. Apply at least 5 gallons of 10-34-0 and 1 quart per acre of chelated zinc in pop-up. That rate is too aggressive on sandy soils but should be fine most years in a silt or silty-clay loam, Bower says. Drop back to 3 gallons plus zinc in sandy soils.

If you apply in a two-by-two band, it takes seedlings more time to get to the nutrients. You may see some early stunting of corn with fallow syndrome before seedling roots reach the band of fertilizer, Bower cautions. She adds that banded starters tend to work much better in these situations than applying additional phosphorus fertilizer by some other method.

3. Consider fungal products. There are some mycorrhizae fungi products developed to add to an in-furrow starter fertilizer, Bower notes. MycoApply EndoPrime by Valent is one such product. She’s not aware of testing in fallow situations.

Valent’s Riffle says MycoApply EndoPrime SC contains four species of mycorrhizal fungi designed to get corn off to a strong start. This in-furrow product can easily be applied via water or starter fertilizer to fit seamlessly into existing cropping practices.

4. Plant soybeans. One option is to plant soybeans in 2020 following prevented planting acres, Bower says. Soybeans are usually much less subject to any negative effect.