Soil Temperature, Planting Depth

Jason Woodward

Jason Woodward
Texas AgriLife
Plant Pathologist

Planting has begun in the High Plains, but some producers have held out for precipitation. Adequate soil moisture is required for uniform germination. As the seed imbibes water, cell division and elongation occurs, resulting in the embryo rupturing the seed coat, and the seedling emerges. Once this process begins, it is important that it continues because plants are sensitive to desiccation at this time.

Some producers apply pre-plant irrigation to ensure adequate moisture. Others plant into dry soil conditions and “water up.”

Although this may be an option, there are potential negative consequences. Peanut seed will germinate under a wide range of temperatures, but a minimum average soil temperature of 65 degrees Fahrenheit at the 4-inch depth is advised, followed by a favorable forecast. Peanuts should crack the ground in seven to 14 days.

treated peanut seedFrequent use of irrigation can reduce the soil temperature, slowing germination and emergence. These conditions favor the development of soilborne fungi that cause seedling disease. Peanut seedlings also can emerge from deeper planting depths.

However, the deeper planting depth increases the amount of time tender seedlings are exposed to disease fungi in the soil.

Plant roots develop rapidly, growing at a rate of 1 inch per day as long as soil moisture is adequate. Roots will not grow through dry soil, and failure to meet stored subsurface water will result in a shallow-rooted crop. This can be detrimental to achieving optimal yield and quality as water use increases with peak demand, approximately 1.5 to 2 inches per week, being required for flowering and pegging through pod development.

Significant yield loss can occur if rainfall is limited or irrigation capacity declines in the latter part of the season and adequate moisture isn’t available in the lower soil profile. Soil moisture is also important to ensure the survival of Rhizobia after planting, facilitate the movement of pegs into the soil and absorption of calcium during pod development. For more information about water requirements, contact your county Extension office.

Acreage And Disease Risk

Scott Monfort

Scott Monfort
University of Georgia

The 2018 growing season is underway with planting as early as April 10 in South Georgia. Be mindful of the weather and moisture before planting. Planting into subpar conditions will only guarantee poor stands and/or the purchase and replanting of seed to get an adequate stand. This will cost more time and money compared to waiting until conditions are suitable initially.

Another key growers need to remember during planting is that peanut seed is a living organism, and storage can make a difference in maintaining the percentage germination and vigor over time. Peanut seed stored in a place that has extreme temperature swings, like an enclosed trailer, for an extended period can reduce seed quality and cause problems with stand establishment. Remember to plant seed in the order in which it was picked up from the peanut buying point (first in, first out).

During production meetings, someone asked, “Will the decrease in peanut acreage help with reducing potential disease?” The answer is, “Not in the short term.” It will take several years of acres below 700,000 before rotations will be corrected. With peanut rotations continuing to be stretched in some areas, many acres remain at a moderate to high risk for disease development.

Determine disease risk by evaluating your production practices using Peanut Disease Rx at the following link https://t.uga.edu/43C. This is an important step in determining how aggressive a grower needs to be in managing potential disease issues based on risk.

Growers with high-risk fields need to consider using a premium fungicide program to manage disease potential rather than a more basic fungicide program. Talk with your county agent regarding the different fungicide programs and how they might benefit you.

Early Weed Control Measures

David Jordan

David Jordan
North Carolina State University

May brings many early season management decisions. Making sure weeds are controlled is one of the most important. The majority of peanut in the V-C region are planted in conventional tillage systems, and it is always a good practice to incorporate some herbicide prior to planting. It takes time to incorporate herbicides uniformly, but this investment will be well worth the effort. At least some weed control will be obtained with incorporated herbicides even under dry conditions.

A DNA herbicide, one that contains pendimethalin or ethalfluralin, is a good start for control of pigweed, other broadleaf weeds and annual grasses – especially Texas millet, also called Texas panicum.

Chloroacetamide herbicides, which are products that contain metolachlor, acetochlor, or dimethenamid, can be incorporated, but make sure the rate matches the soil texture/organic matter content. For some growers, the time required to till and incorporate is simply not there.

For those in conservation tillage, the ability to incorporate is challenging. In these cases, apply residual herbicides, such as the chloroacetamide herbicides, at several timings early in the year. This increases the likelihood of catching a rain for activation.

Preplant, preemergence, at cracking and early postemergence timings, all within the first few weeks after peanut emergence, are good times to get herbicides with residual activity in the field.

A new chloroacetamide herbicide, Zidua, fits in the postemergence timing quite well. Of course, if some weeds are up, applying these herbicides with an appropriate contact herbicide, such as paraquat, is critical. The extra money spent early in the season on weed management will often pay for itself through protection of peanut from weed interference and by reducing the need for extra postemergence sprays later in the season.

As these applications are being made, it is generally OK to apply acephate to control thrips with these herbicides if systemic insecticides applied in the seed furrow did not perform well. Be careful not to apply paraquat if peanut injury from thrips is excessive. In most instances, if a systemic insecticide was applied in the seed furrow at planting, there will be enough protection from thrips to allow paraquat to be applied with no concern of excessive injury. But, if there is considerable thrips injury, applying paraquat will reduce yields.

From a resistance management standpoint, the herbicides I have focused on here have held up quite well in terms of evolved resistance in weeds. Although the DNA and chloroacetamide herbicides do not have significant post-emergence activity and paraquat (with Basagran) needs to be applied when weeds are small, these herbicides serve as good tools to reduce selection pressure on ALS inhibitors (imazapic and diclosulam) and PPO inhibitors (acifluorfen, flumioxazin, and lactofen).

Label Change In Alabama

Kris Balkcom

Kris Balkcom
Auburn University

Because of cool soil temperatures in April, planting is just now getting into full swing. Producers need to be aware of the label change for Strongarm use in Alabama peanuts.

Alabama received a Section 24(c) label for Strongarm in June 2017 for an over-the-top treatment. Before, it could only be used as a pre-emergence herbicide treatment. This will give you some herbicide options at planting for the 2018 crop.

The change is mainly because of tropical spiderwort (bengal day flower). If you have this weed in your field, I encourage you to use Valor behind the planter as a pre-emergence herbicide for pigweed and spiderwort control. Then you could use Gramoxone, Cobra or Ultra Blazer as a burndown spray for escaped weeds. At this time, you could add Strongarm for control of spiderwort, morningglory, bristly starbur and Florida beggarweed, and add Dual Magnum for spiderwort and pigweed residual control.

This will stretch out your residual herbicides for a longer period of protection against this troublesome weed.

I hope this will be helpful information to those of you who have this weed and may be unaware of the label changes with this herbicide.