Flooding effects on soil biodiversity

What you'll learn: 

  • Flooding in a field prior to planting may lead to “fallow syndrome” in the crop due to a decrease in soil microbial communities

  • Utilizing an inoculant at planting may help increase the beneficial rhizobia populations in soybean fields

  • Using an inoculant for corn may improve the availability of phosphorus


Fields that recently experienced flooding before planting may have reduced soil biological diversity. The decrease in soil microbial communities following flooding is due to the depletion of oxygen in the soil profile. Silt deposited by a flood may add to the problem by sealing the field and further preventing oxygen from entering the soil. Fallow syndrome is the nutrient deficiencies and reduced growth of a crop that result from the absence of sufficient populations of beneficial soil microbes and can dramatically affect crop production.

Effects of flooding in soybean fields

Long periods of soil saturation and anaerobic conditions (three days or longer) decrease populations of the nitrogen-fixing rhizobial bacteria. Soybeans need rhizobia for optimal nitrogen fixation and without this beneficial bacteria, significant yield reductions can occur1.

When planting into a field that was previously flooded, the use of rhizobia inoculants may improve root development, nodulation, vigor and plant stand establishment, which can lead to faster canopy closure, better plant health, higher yields and a higher return on investment (ROI). In addition to these benefits, rhizobia inoculants provide the convenience of retail application and can be used in tandem with fungicidal and insecticidal seed inoculants.

TagTeam® LCO and Optimize® products combine nitrogen-fixing rhizobia with the LCO molecule — a combination that, based on a 2016 growth chamber study, can result in 2X as many nodules compared to rhizobia alone. Plus, the LCO enhances mycorrhizal colonization, which increases functional root volume and helps the plant uptake more water and nutrients through the roots.

Effects of flooding in soybean fields

Corn and small grains that have been planted into a field following flooding may show symptoms of phosphorous or zinc deficiency accompanied by slow, uneven early growth and stunting. These deficiencies are often due to a decrease in populations of vesicular-arbuscular mycorrhizal fungi, which act as an extension of corn roots. The LCO in BioRiseTM Corn Offering* enhances mycorrhizal colonization, which increases functional root volume and helps the plant absorb additional nutrients.

QuickRoots® technology helps maximize corn yields — especially in fields with limitations in moisture or nutrient availability. The microbes in QuickRoots technology help increase the availability and uptake of phosphate, which increases root volume. With more root volume, the plant can access additional nutrients, including nitrogen and potassium, protecting it from stress.


*Class of 2017, 2018, 2019 and 2020 base genetics are treated with either BioRiseTM 360 ST or BioRiseTM 2 Corn Offering (the on-seed application of the separately registered products Novozymes® B-300 SAT and BioRiseTM 360 ST).



Staton, M. 2014. Identifying and responding to soybean inoculation fail- ures. Michigan State University. http://msue.anrmsu.edu.

Other sources: Ellis, J. R. 1998. Post flood syndrome and vesicular arbuscular mycorrhizal fungi. J. Prod. Agric. 11:200-204. Monsanto BioAg 2016 Product Guide. Web source verified 2/29/16.

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