Idle acres at risk: Fallow syndrome reduces soil health

PLANO, Texas — A record 19.4 million acres nationwide were without row crops last growing season due to poor planting conditions and those left fallow are at risk in 2020 without the proper management practices.

Brian Cornelious, Agricen director of applied sciences, said unplanted acres are susceptible to fallow syndrome — primarily defined as a phosphorous deficiency — that reduces an important fungi in the soil.

“Vesicular arbuscular mycorrhizae fungi are very important to the row crop system and basically act as an extension of the plant root systems. The fungi are able to capture water and nutrients and funnel that back to the plants,” Cornelious said.

“The mycorrhizaes also depend on plant roots in that system to provide nutrition for the mycorrhizae to survive. Mycorrhizae are dependent on having some type of plant in that system for them to support their life cycles. In the absence of plant roots you’re also affecting the populations of those mycorrhizae that are helping improve plant growth and productivity.”

Fallow syndrome symptoms in corn include purple coloration, or phosphorous deficiency, short or stunted or uneven plants.

In many cases, cover crops were used in 2019 on prevent plant acres to provide erosion protection, prevent weed growth, improve soil tilth and provide forage for Vesicular arbuscular mycorrhizae populations.

Options

Looking ahead to 2020, Cornelious gave the following recommendations on managing those acres that did not have cover crops and were left fallow:

• Apply starter fertilizers. Banded phosphorous at 60 to 80 pounds per acre plus zinc; higher rates should be placed 2x2 to avoid damage from the nutrients.

• Alternative crops. Soybeans and sorghum are more tolerant following fallow soil. So, as opposed to following the fallow field with corn that's very susceptible to these conditions, these other options should be considered.

• Inoculants. Use to rebuild VAM populations; often not feasible because of the cost.

• Use Extract Powered by Accomplish biocatalyst. Technology designed to help release of phosphorous, zinc and other nutrients for greater availability to plant.

“Extract is a proprietary technology that’s a combination of biocatalyst technology and a nutrient source. So, when we look at biocatalyst technology in Accomplish combined with nitrogen and sulfur applied in this system it can actually help us get more out of that system from a nutrient standpoint to release nutrients that are tied up in that system that could be contributing to that fallow syndrome,” Cornelious said.

He added that farmers cannot depend on the nutrients they applied last spring on acres that ended up being fallow.

“In a perfect world you should be able to plant the crop in 2020 and depend on those nutrients that were previously applied, but in most cases those nutrients are bound or have been used by some other mechanism in the soil and the crop doesn’t have access to those nutrients. There could be some residual there, but we need to use some technology to get the maximum benefit of those nutrients that are in the system,” he said.

Prevent Plant Numbers

Nationwide there were 19.4 million prevent plant acres reported to the Farm Service Agency. There were 22 states with more than 100,000 unplanted acres. Illinois had 1,505,661; Indiana, 944,680; Iowa, 463,315; Missouri, 1,399,103; and Wisconsin, 595,090.

U.S. corn prevent plant acres were estimated at 11.2 million acres. Forty-four states reported prevent corn acres and 15 states had more than 100,000 unplanted corn acres. Illinois had 1,143,131 acres; Indiana, 710,241; Iowa, 380,822; Missouri, 749,444; and Wisconsin, 459,042.

FSA reported 4.1 million acres of soybeans were not planted nationwide. Fourteen states reported 100,000 or more prevent plant soybeans acres. Illinois was 331,581 acres; Indiana, 230,366; Missouri, 482,685; and Wisconsin, 125,536.

There were 2.1 million wheat prevent plant acres in the country. Eighteen states had more than 25,000 unplanted wheat acres including Illinois at 27,063 acres and 84,678 in Missouri.