Peanut Pointers: June 2024

Meeting The Calcium Need For Good Pod Fill

Many growers are trying to reduce their input costs. In trying to do so, questioning the need for gypsum and/or considering using something cheaper or easier is always part of the equation. The value of calcium and the need to determine if a crop has adequate calcium levels has remained consistent, year after year. Here is an excerpt from a county agent article written by former University of Georgia Extension peanut specialist John Beasley and current UGA soil scientist Glen Harris from 2009 that still rings true today.

“To determine if you need calcium, producers need to take a “pegging-zone” sample to determine if there is adequate calcium for pod development, increased yield and improved grades. The pegging-zone sample is taken at the three-inch depth. The calcium that peanut pods take up is absorbed directly from the soil surrounding the pods. The peanut plant cannot translocate calcium in the plant down into the pod. Do not take the sample any deeper than three inches.

“Pegging-zone samples need to be taken as soon after emergence as possible to get the results back and the calcium applied by the time the plants initiate blooming. Our standard UGA recommendation for calcium nutrition is to add supplemental calcium in the form of gypsum (land plaster) if the sample from the three-inch depth has less than 500 pounds per acre of calcium or if there is less than a 3:1 ratio of calcium to potassium.

“Another concern we have is that some liquid products are being promoted as a source for amending calcium deficiencies. The UGA recommendation for calcium nutrition for peanuts being grown for commercial, edible use is to apply 160 to 200 pounds per acre of elemental calcium per acre. Most gypsum products are about 20% calcium, so it requires 800 to 1,000 pounds per acre of gypsum to meet that requirement. If a field is being grown for seed production, then the rate is doubled to 1,600 to 2,000 pounds per acre.

“If one of your producers is asked to apply a liquid product, then they need to know what percent calcium is in the product and what the recommended rate is. For example, if a liquid product has 10 pounds of calcium per gallon, then it would take 16 gallons per acre of the product to deliver the minimum requirement of 160 pounds of calcium. Some liquid products list the calcium in the product as a percentage. For example, if the product is listed as 10% calcium and the liquid material weighs about 10 pounds per gallon, then you are getting about one pound of calcium per gallon and would need 160 gallons per acre to meet the minimum requirement. Be careful of products that state the calcium is absorbed by the tissue for use by the pods. The plant cannot translocate the calcium from the leaf tissue to the pods.

“There are also some lime products being pushed as a pegging time calcium amendment. Lime is calcium carbonate compared to gypsum (land plaster), which is calcium sulfate. The calcium carbonate (lime) will provide calcium in an available form eventually, but if applied after planting, the calcium becomes available much later than needed. If the lime was applied before planting, then it has time to break down into an available form. This also goes for ‘fine’ lime, which has smaller particles. The bottom line in calcium nutrition is that if the calcium source is applied at early bloom, it needs to be gypsum at the rate of 160 to 200 pounds per acre of calcium or double that rate for seed production. Do not apply a liming material at early bloom or pegging.”

As always, contact your local county Extension office if you have any questions.

Reminders With Recent Rains

I feel that many producers may be behind on finishing up planting this year due to the rains during the middle of May. Early in the peanut planting season, we had good conditions coupled with warm soil temperatures, which led us to some nice-looking peanut stands to start the season. I say that some may be behind, depending on the amount of rain during mid-May. Many were out of the field due to the wet conditions from May 10-22. However, we know as well that song by Luke Bryan, “Rain is a Good Thing.” Many farmers had stopped planting waiting on moisture right before this time.

Timing is everything in farming, and this year like many other times in the past, if you didn’t start early you wound up late. Therefore, if you’re in this category, first of all, you’re not alone. Hopefully, the weather will be the opposite of last year and late peanuts will be fine as long as we have moisture later during the growing season. Now, with planting finishing up, many farmers will have a pretty large planting gap across their acreage this year.

Don’t forget how long it’s been since the first planting. With higher temperatures we have seen coupled with this moisture and humidity early, we will have to take the necessary precautions and start treating with fungicides early to protect the crop this year.

Also, some folks like to put gypsum out really early in the season; however, if you got seven to 10 inches of rain during the middle of May, remember, gypsum is very water soluble. Therefore, if you did apply it early, you may have very well lost some of it and need to reapply.

More Isn’t Always Better

When June comes around, there are key inputs and practices that need our attention in a timely manner. One is firming up weed control. Herbicides applied at planting as well as early postemergence applications have hopefully been successful, but there is a lot of season remaining. Not only do weeds compete with peanuts for light, water, water and nutrients, plus space and essential gases like CO2 as well, but they also interfere with digging and vine inversion and can keep fungicides and insecticides from reaching the right place in the canopy.

We recommend overlapping residuals for control of weeds. Complement your preplant burndown or preplant incorporated sprays and herbicides applied right after planting (preemergence) with additional residual herbicides applied with contact herbicides (paraquat plus Basagran mixtures and PPO-inhibiting herbicides), Cadre/Impose and clethodim products. This can seem expensive, but early season weed control is critical, and we need season-long control for efficient digging. If we don’t disturb the soil, we will have controlled the major flushes of weeds with overlapping residual herbicides.

A second important practice is to control thrips with postemergence insecticides. Be timely with these sprays. By the time you read this, the early planted peanuts will have already needed follow-up sprays of insecticides. Don’t spray paraquat on peanuts with significant injury caused by thrips. You will get a major yield hit in many cases.

For Virginia-market types and large-seeded runner-market types, apply gypsum at rates recommended by Cooperative Extension. Rates for various products can be found in the North Carolina production guide “2024 Peanut Information” on all Virginia-market types. I recommend at least half that rate on runner-market types. There is a tendency to apply gypsum in early June.

Sometimes peanuts are very small at that point in the season, and big rains can wash the gypsum from the top of the row into the furrow since many acres in our region are planted on beds. I suggest later applications when peanut plants are bigger. The plants minimize washing of gypsum from where it is needed if you get heavy rains, and the alternate application increases the likelihood that adequate calcium will be in the pegging zone throughout the season.

At times, we think that more gypsum than the recommended rate gives us insurance. However, in some of our research, we find that rates higher than the ones we recommended can actually decrease yield, if we have low-pH soils. I do not recommend higher rates than what we have in the guide. There will not be a yield increase above the recommended rate, and in areas of the field with lower pH, yields might be lower than yields without gypsum.

Staying ahead of micronutrient deficiencies is important. In fields with high pH, we need to address manganese deficiencies early, and peanuts might need multiple applications. Make sure the products you purchase deliver adequate manganese and boron. There is not a magic formulation on the market. The formulation you use has to have enough micronutrient to make a difference. We also cover some of these products in “2024 Peanut Information.”

As we move into late June and early July, putting a solid program in place for leaf spot and stem rot management is critical. In North Carolina and Virginia, we generally have a five-spray program that begins at the R-3 stage of peanut growth and development, but no later than July 10, if you are spraying on a 14-day schedule. We have weather-based advisories for leaf spot that can help target the timing of sprays. The first and last sprays need chlorothalonil — multiple formulations are available. There are many options for sprays two, three and four to control stem rot and leaf spot. Some fungicides provide protection from leaf spot and stem rot for different lengths of time. The keys are to make sure there are no gaps in protection and resistance management is practiced by using the correct fungicide rate, applying the number of applications based on recommendations and alternating sites of action.

Finally, there is a great deal of overlap between sprays for weeds, insects and diseases and products we apply to address nutrient deficiencies and manage vine growth. Before you put a host of products in the tank at the same time, ask around and make sure the products are compatible. We don’t want to get less control than desired, more crop injury than we can stand, and we certainly don’t want to have to discard many acres of pesticides that settled out in the tank or replace parts of sprayers.

Check For Active Nodulation

Most peanuts in the Southwest have been planted. June is a good time to make an initial assessment of peanut nodulation. Peanuts form a symbiotic relationship with Rhizobium spp. and fix atmospheric nitrogen, if an inoculant was properly applied at planting.

A study conducted in England showed effectively nodulated peanuts with supplemental nitrogen fertilizer were more adaptable to hot environments than those relying solely on high amounts of nitrogen fertilizer without inoculation. This could be associated with more efficient nitrogen formation by Rhizobium spp. The study is highly relevant to Southwest peanut growing conditions, where the top four inches of soil temperature peaks at 97 degrees Fahrenheit in the growing season. (Photo 1)

To assess the early season nodulation status in your peanuts, carefully dig plants and count the number of active nodules. Active and healthy nodules should appear reddish pink inside due to the reaction of leghemoglobin (Photo 2). If the center of nodules is dark green and/or black, the rhizobia is inactive. Check to see that the plant has more than 20 active nodules in five to six weeks after planting. If the number of active nodules is less than 10, peanuts will benefit from the mid-season nitrogen program. Applying 10 to 20 pounds per acre of supplemental nitrogen should be sufficient. Do not exceed 50 pounds per acre as excess nitrogen may increase the chance of pod rot later in the season.