Inoculant Guide: Q & A

Screen Shot 2015-11-01 at 1.44.47 PMQ. What is the benefit of using an inoculant?

A. As a legume crop, peanuts can supply their own nitrogen, but only if rhizobia bacterium is available in the root zone and in close proximity to the emerging seedling to enter into the root and begin fixing atmospheric nitrogen. To do this successfully, there must be a sufficient quantity of fresh, vigorous bacteria ready to move into the roots and multiply quickly. This is the most efficient and sustainable means of supplying nitrogen to the peanut plant.

Today’s inoculant products also may contain more than the peanut-specific robust bacteria the plant needs. It may also contain protection against seedling disease. For example, Vault Liquid Peanut plus Integral combines BioStacked technology with Integral biofungicide for enhanced root vigor, nutrient uptake and suppression of Rhizoctonia and Fusarium root rot, providing even more protection for peanut yield potential.

Well-nodulated peanut plants
Well-nodulated peanut plants

Q. Should I apply an inoculant every year?

A. Bacteria can survive in the soil for many years, but today’s inoculant products are far superior to bacteria found natively in the soil. Producers need a product that is ready to colonize in the root, form nodules and begin _ xing nitrogen as quickly as possible. Because it is a live organism, rhizobia already in the soil and not applied fresh at planting has spent its energies just trying to survive in the soil and may not be the vigorous product producers need.

In the Southwest, fresh inoculant must be added every year because of the harsh field conditions. Liquid, in-furrow products have been found to work best in arid, dry soils. In the Virginia-Carolina area, where flooding has occurred, water-logged soils will have depleted oxygen levels making it impossible for rhizobia to survive. In the Southeast, a combination of high temperatures and/ or water-logged soils may create conditions wherefore applying an inoculant is simply a sound investment into the crop.

Q. Will soybean inoculant work in peanuts?

A. No. The product may be similar in name, but the species of bacteria needed for these two legume crops are different. Bacteria know what their primary host is and the signal chemicals sent out from the roots of the soybean are different than those sent out by peanut. The soil is full of many different types of bacteria, but those signal chemicals tell exactly which bacteria to respond. Putting a soybean inoculant on peanuts is simply wasting money.

To get the benefits of nitrogen fixation and the resulting vigorous root growth, disease protection and, ultimately, a boost in yields, an inoculant specially produced for peanuts should be used.

Q. What is important about the handling and application of an inoculant product?

A. An inoculant should be bought fresh each year for maximum viability. Inoculants should be kept completely away from direct sunlight, and are best stored at temperatures from 40 to 77 degrees Fahrenheit. Do not freeze the product. Once a package has been opened, use it within 24 hours.PG Nov 15.indd

At application, make sure the inoculant is placed in direct contact with the seed for maximum uptake. If planting conditions are less than ideal, consider using a little more than the recommended rate. If water is used as a carrier for the inoculant, chlorine-free water, such as well or rain water, should be used.

Refer to the product label for further care and handling instructions and for application rates.

Q. How can I get the best efficacy from an inoculant product at planting?

A. Rhizobia want to be in the soil and ready to move into growing peanut seedling roots to begin converting atmospheric nitrogen into something usable for the plant; it’s the sole purpose of their existence. This all starts with selecting the right product fresh every year. Then, it needs to be stored and handled properly in that time between delivery and planting, as mentioned above.

At planting, proper calibration of application equipment is important. Check all nozzles and spray tips, and make sure everything is clean, in working order and calibrated correctly.

Remember that heavy applications of nitrogen fertilizer too soon after planting may hurt or lessen the activity of the rhizobia bacteria. Nitrogen-fixation through the symbiotic relationship with peanut-specific bacteria is the best, most efficient and sustainable way to supply the plant with nitrogen.

Q. How do I choose the right product for my fields?

A. Inoculant products are thoroughly field tested. Evaluate university field trials, in your area if possible, to determine what inoculant product might work best in your production system.

Without adequate nodulation, you won’t have the yields you need. What a grower should look for in an inoculant product, first and foremost, is something specific to peanuts. You need a product with a high volume of rhizobia in it – such as can be found in liquid inoculant products, which provide a lot more rhizobia than other formulations.

Q. How do I know the inoculant is working?

Active Nodules
Active Nodules

A. Peanut growers should target two key times to scout their nodulation. First, scout five to six weeks after planting to assess early nodulation in advance of decisions about applying mid-season nitrogen. Second, checking late-season nodulation from mid-August to early September will confirm early observations and or flag fields that nodulated poorly. For poorly nodulated fields, try to examine why nodulation did not occur to the amount desired and what can be done to enhance nodulation in next year’s crop. Obvious signs where the inoculant was misapplied are yellow rows or even spotty green/yellow areas throughout the field or light pea-green field color suggesting nitrogen deficiency. Common causes of minimal to no taproot nodulation despite inoculant application are as follows:

  • Poor placement of in-furrow granular or liquid inoculant. Make sure the liquid stream is coming right in on top of the seed and that granular drop hoses do likewise.
  • Shallow planting, less than one and a half inches, especially at one inch, particularly for liquid inoculants, where surface soil may become hot or dry out. Death of inoculum and reduced nodulation may also occur when little soil is drug back over the seed even if planted deeper.
  • The use of starter fertilizer near the seed at rates beginning near 30 pounds per acre. This will reduce nodule development, and larger applications of mid-season nitrogen can reduce peak nodulation as peanut plants take the lazy approach and use the fertilizer before fostering nodule development.
  • Incompatibility with other products applied at planting. Always read and follow the label for product compatibility or consult your inoculant company representative.

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