The Loss of Microbes to Feed Plant Roots

Throughout much of the Central and Eastern Cornbelt soils are saturated. Thanks to a June which set precipitation records in Illinois, Indiana, and Ohio, corn and soybean fields are waterlogged. Tiling has mitigated some of the problems with excess water, but aerial photos show water standing in large areas and crop scouting has become a process of slogging through fields with wading boots.

Flooded Corn Field

Flooded Corn Field

However, that crop scouting may come to a quick end. It will be unnecessary to walk through fields of dead corn and soybean plants if the water does not recede, allow the soils to dry out, and the microbial life to return to normal in its job to feed nutrients into corn and soybean roots. That necessary process is severely reduced to the point of being eliminated in soils that are totally saturated.

Anaerobic microbes don’t care. But aerobic microbes which thrive on oxygen, important for nutrient uptake by row crops, do care. Footnote: (1) They require soil that has enough air pockets to allow oxygen to get to them. Otherwise they drown, just like any other air-breathing creature which is trapped in water.

When the microbes no longer function, they no longer can channel N, P, K, and other nutrients into the roots of corn, soybeans, and other plants, and the plants starve. Most of the time, the finger of blame is pointed at the water, with the accusation that it drowned the crop. Most crops, with the exception of rice, do not like “wet feet.” But there is a difference between having wet feet, in a literal sense, and starving. Most of us would be able to get along with wet feet, but we could not survive without food, and that is what is happening to billions of corn and soybean plants across millions of flooded acres in the Cornbelt.

Water Damaged Corn

Water Damaged Corn

Although their crops have depended on it, many farmers are not aware of the impact of beneficial microbial activity on plant roots. Essentially, microbes cluster around the plant root, digest the nutrient molecules, and feed the basic elements into the plant. The corn plant grows, produces an ear, and with the help of the marketplace the process will resume the following growing season on that farm. But when the phenomenal growing season of 2014 dovetailed into 2015, there were a lot of changes.

The 2015 planting season was delayed because of cold soils. Many farmers planted seed because the calendar said it was time to do that, and they were betting on warmer soil temperatures in days to come. But the soil stayed cool, the microbes continued to hibernate, and seed germination began with a very slow start.

Then the rains came. Soils remained saturated and planting was delayed until there were adequate weather windows to get most of the job done. But continuous thunderstorms, reminiscent of an unending string of pearls, brought incessant rainfall. The soil remained wet, crops did not have to extend their roots very far to get moisture, and subsequently plant roots are unusually short. But short roots have a limited ability to feed the nutrient needs of the growing plant; consequently there is insufficient food for grain production. The corn plan has a conundrum. Does it halt its reproduction cycle or does it pull nutrients from within itself. Mothers know best.

Corn Feeding Upon its Own Nutrients

Corn Feeding Upon its Own Nutrients

Lacking nitrogen and other nutrients from soil sources, the plant begins feeding on itself, and a race begins between plant maturity and plant death. Ironically, the race is run on a wet track, but the track has been just too wet for soil microbes to do their job and keep the plant fed and alive long enough for it to produce an abundance of good quality seed.

Stu Ellis
Cornbelt Ag Contributor
@Farmgateblog

(1)
https://books.google.com/books?hl=en&lr=&id=8_DPNNEUAikC&oi=fnd&pg=PA15&dq=soil,+excess+water,+microbial+activity&ots=BV6TLgBP65&sig=mla7vpsCqWwJPfJyt9-5fvehoUk#v=onepage&q=soil%2C%20excess%20water%2C%20microbial%20activity&f=false
(beginning on page 20)

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