Inoculant may be needed for peanut planting

Published 10:05 am Wednesday, April 23, 2014


ISLE OF WIGHT—A recent article in the Southeast Farm Press indicated that peanut fields may require the use of inoculant due to an excessively wet fall and winter. Since the article addressed conditions further to the south than Virginia, I asked Dr. Maria Balota [Assistant Professor of Crop Physiology at the Tidewater Agricultural Research and Extension Center in Suffolk] if this is something Virginia peanut growers should also consider. Her response is below:

“Yes, I would recommend use of Optimize Lift at 16 oz/A in furrow at planting and regardless the number of years of rotation; in other words, for all fields. Below is the section in the Peanut Guide related to the use of inoculants and how to apply to be effective. Please be advised that any inoculant is a living product made out of bacteria and, as such, caution needs to be paid at handling it. Producers need to ensure that the inoculants are not kept in either too cool (freezing) or too high (over 95 F) temperatures. Keep the inoculant in shade when brought into the field for planting. They should not plant when the soil is very dry (not to worry about it this year, I guess!). Also they need to question the seller how the inoculant was stored; acceptable temperatures are 45-95 F or else it will be ineffective.

Use of Inoculants (pg. 18-19, 2014 VA Peanut Production Guide)

“Peanut is a legume and as such can get most of its N needs from nitrogen-fixing bacteria (Bradyrhizobium) colonizing the plant’s roots.

To provide these needed bacteria, you absolutely must inoculate all “new” peanut land, and should also inoculate strip-tillage fields and land that has been out of peanut production for three years. Research at Clemson University showed that inoculation gives yield advantage even in soils regularly grown with peanut. Use liquid in-furrow inoculants. In-furrow granular inoculants are less effective than liquids and usually stop-up in the delivery tube. Seed treatment inoculants are not recommended due to having much lower bacterial counts. Inoculants are living organisms; treat them with care and make sure they are not out-of-date.”

Inoculant rules:

• Use only liquid in-furrow inoculants. Granular and seed treatments are less reliable.

• Do not expose to heat during transport and storage

• Use a minimum of 5 gallons of water per acre.

• Make sure the inoculant stream hits exactly in the center of the open furrow, not the dry furrow walls. Trash caught in strip tillage rigs can deflect the inoculants stream.

• Don’t plant too shallow (less and 1.5”) or in dry soil. Inoculant must hit moist soil or it will die.

• Do not use chlorinated water.

• Apply with a steady stream, not a pulsing pump.

Poorly inoculated fields usually will not show any yellowing until about 45 DAP. Inoculation can be checked by using a shovel to uproot plants. Simply pulling up plants will cause the lower taproot to break off and result in a low count. The presence of large (1/8” or larger) nodules on the taproot indicates successful inoculation. An average of 15 large nodules per taproot at 45 DAP is considered good; less than 10 per taproot is marginal and less than 5 indicates poor inoculation. If only small (1/16”) nodules are present and these are mostly on the lateral roots rather than on the taproot, the plant has probably only been colonized by native Rhizobium bacteria, not the applied inoculants.

If inoculation fails, either by application of inoculants or natural inoculation, broadcast ammonium nitrate (375 lb/ac of 34 percent = 127 N units) or ammonium sulfate (600 lb/ac of 21 percent – 126 N units) can be used. Failure of natural inoculation can be expected in very dry planting seasons. If the canopy has not closed, liquid N can be dripped in the row middle. Foliar nitrogen applications are not cost effective and often cause unacceptable leaf burn.

Boron needs for peanut
From Balota’s Peanut Notes No. 9

“My program folks usually apply the first shot of boron 9 percent (1 qt/A) with Prowl or Intrro herbicides either pre- or post-planting, and the second (also 9 percent, 1 qt/A) in mid- to late-July. This recipe was developed by Walt Mozingo and I am not sure if it is better than solely foliar applications, but I will find out soon as I plan an experiment for it this summer.

“Our soil tests this year, show less than 0.1 ppm boron (which is 0.2 lb/A) in all fields dedicated for peanut planting. This is expected due to the amount of rainfall we received, but needs to be corrected. Usually, if the soil tests read less than 0.5 lb/A boron, 0.3 to 0.5 lb/A boron should be applied.

Keep in mind that the border line between boron deficiency and toxicity is slim, meaning that if applying boron just a little over what plants need, they may develop toxicity (there may be no visible toxicity symptoms, but I am sure this can induce a nutrient imbalance in the plants with possible negative effects on yield).”