Don’t Forget About the Nodules!

Photos: United Soybean Board/Flickr

By Jason Ladman, Director of Sales, Big Cob Hybrids

Ag has been turned upside down and life as we know it has changed, but for the soybean plant, it is business as usual.  The plant still needs to obtain a certain amount of the correct nutrients in order to produce actual soybeans and one of the biggest volume nutrients required is nitrogen.

When we talk about soybeans, we typically do not think about nitrogen as a limiting factor because we rarely apply nitrogen to our soybean crop.  Soybeans use about five pounds of nitrogen for every bushel produced, which means if the plant is going to pump out 70-bushel soybeans, it will need 350 pounds of nitrogen.

What makes soybean plants special is that they can make this nitrogen on their own. The plants get some of the nitrogen they need by working with specialized bacteria in the soil. These bacteria live in root nodules and pull nitrogen from the atmosphere and convert it to a form the plant can use – a process known as nitrogen fixation. However, if conditions are not correct, the soybean plant may need your help via inoculation.

Anyone that has ever planted soybeans knows the importance of inoculating soybeans and the role the rhizobia bacteria play in the nitrogen fixation process.  However, when commodity prices are low, it is common to look for ways in which to cut expenses. Often, soybean treatments and inoculation are on the chopping block.

Here are some situations in which inoculation has proven to be worth the expense:
  • First time for planting soybeans in five or more years – Environment plays such a large role in the survivability of the rhizobia bacteria that once a field has been absent from soybeans for around five years, it is a good play to inoculate.
  • Lower Soil pH – Low soil pH can decrease nodulation and nitrogen fixation and it can manifest itself when the environment is particularly challenging during a period of drought or flood.  Optimal soil pH is around 6.8 pH.  If you have skipped on the lime application this year due to the expense – do not skip out on the inoculation.
  • Floods and Drought – With many fields directly affected by standing water as a result of the 2019 crop year, there is a strong chance that the survival of the rhizobia bacteria could have been jeopardized as bacteria needs oxygen to survive.  In fields where excessive water was an issue the previous year, it is recommended to inoculate.
Little or No Nodules? What are the signs?

On occasion we receive a phone call about a soybean field that does not appear to be growing.  Upon inspection it is often discovered that the soybeans did not put on adequate nodules. It is always hard to determine why this happens, but many times it is a result of one or more of the above situations.

If you see short and lighter green soybean plants in late June to early July, you should suspect poor nodulation. The best way to tell if this is the problem is to dig up plants in the affected areas and examine the roots. If you find fewer than seven nodules per plant, then you can assume this is the problem.

Research has shown that if discovered soon enough an application of 60-70 lbs. of actual nitrogen per acre can correct the nitrogen deficiency and still provide an economic return. Urea is typically the best nitrogen source that will cause the least amount of damage to the foliage.

If you find yourself looking at an unhealthy soybean field during the early summer months – do not forget about the nodules – because capturing every potential bushel in 2020 will be imperative.

Have questions or need help? The Big Cob Hybrids’ team is here to get to the root of your nodule problems! Call us at 402.641.5014 or email sales@bigcob.com.

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