ONE GROWER PUBLISHING, LLC
MARCH 2017
Mix it up Rotate control methods, crops to slow PPO resistance
Irrigation study pits furrow vs. flood
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Flood vs. furrow Study pits irrigation methods against each other in farmers’ fields, gauging water use and costs.
By Jason Krutz and Dan Roach
Water use was similar Surprisingly water use in both systems were similar. This information tells us farmers are doing an extremely good job managing water use in their flood-irrigated fields.
MISSISSIPPI STATE UNIVERSITY
F
rom time to time, the Mississippi State University Irrigation Team is asked to investigate the effects of certain agronomic and cultural practices farmers use. Traditionally, many rice farmers chose to flood irrigate their soybeans. Rice farmers were accustomed to pulling levees in rice fields, so it was a natural fit to irrigate soybeans in the same fashion. With the decreasing water levels in the Mississippi Alluvial River Valley aquifer and state regulators responding by requiring minimum levels of irrigation water-use efficiency practices, the Irrigation Team was requested to investigate furrow and flood irrigated soybeans here in the Delta. During the summer of 2016, eight Delta farms were chosen to participate in a study to compare the water use and yield of furrowand flood-irrigated soybean fields. Each farmer was requested to furnish two fields— one furrow irrigated and one flood irrigated. The fields were required to be side by side or in relatively close proximity with the same planting date and variety. All cultural practices were to be preformed similarly. An MSU researcher installed Watermark moisture sensors in both fields and maintained a record of soil moisture levels. The researcher made the irrigation decision on the furrow-irrigated field while the farmer made the decision on the flood-irrigated field. Irrigation water meters were installed in both fields to measure water use. Combine yield monitors provided the yield results.
Furrow-irrigated fields yielded about 10 bushels per acre more than flood-irrigated fields in a Mississippi State University study.
Furrow Versus Flood Irrigation Yield
Water Use
IWUE
Return
Bu/acre
Acre-in
Bu/acre-in
$
Flood
66.4
8.9
10.8
$154
Riser
76.9
8.6
10.2
$258
0.0143
0.7810
0.7263
$104
P-value
N = 8 farms; No system exceeded permitted value, 18 acre-in/yr; 50% population applied more irrigation water than RISER; Soybean Prices at $10.50
Most farmers implementing flood irrigation have been using this practice for years, mastering when and how to terminate irrigation to minimize runoff. Flood-irrigated yields averaged across locations resulted in a 10-bushel decrease over the furrow-irrigated fields. The number of levees, well capacity, saturation and drainage all played a role in this yield reduction. Farmers continuing to flood irrigate should pay close attention to well capacity and field size as well as drainage, avoiding soil saturation on the top and bottom sides of the field. We will continue this investigation in 2017. Total specified expenses for the furrow-ir-
rigated system were $549.70, which reflected the additional cost of the poly tubing and RISER program equipment (surge valves, sensors, data loggers). Total specified expenses for the flood-irrigated system were $543.23. Net income at $10.50 soybean prices were $258 for the furrow-irrigation system and $154 for the flood-irrigation system. Dr. Jason Krutz is an Extension irrigation specialist based at Mississippi State University’s Delta Research and Extension Center in Stoneville, Miss. He may be reached at ljk81@msstate.edu. Dan Roach is an Extension associate at the DREC. He may be reached at dan.p.roach@msstate.edu.
On the cover: David Caudell, owner and operator of Caudell Custom Harvesting, took the photo using a drone. He and his crew were harvesting soybeans on Mark Gable Farms near Clarksdale, Miss. Rusty Blain is operating the combine in the foreground, with Mark Gable on the one in the upper right. Twitter: @SoybeanSouth
MARCH 2017 SOYBEAN SOUTH
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UNITED SOYBEAN BOARD
Mix it up
Rotate control methods and crops to slow development of PPO resistance in Palmer amaranth.
Season-long competition by Palmer amaranth at 2.5 plants per foot of row can reduce soybean yield by as much as 79 percent, according to information from the United Soybean Board.
By Vicky Boyd Editor
A
lthough two new herbicide-tolerant crop technologies have recently hit the market and a few others are in the pipeline, weed experts say growers should still practice integrated weed management to slow herbicide resistance from developing. “We have new technology coming out, but really, things haven’t changed,” says Bob Scott, University of Arkansas Extension weed scientist. “We’re trading Liberty for dicamba. You still need to follow all of the other recommendations to be successful.” His words take on even more importance as Palmer amaranth, also known as Palmer pigweed, has developed resistance not only to glyphosate but also to a few other herbicides, though on a lesser scale. Palmer pigweed’s resistance to the PPO-inhibitor family of herbicides—often referred to as Weed Science Society of America Group 14—is the latest mutation to challenge growers. Glyphosate is a Group 9 herbicide. Surveys conducted by University of Arkansas weed scientist Jason Norsworthy found the heaviest populations of PPO-resistant Palmer pigweed in northeast Arkansas. In that area, Scott says growers have a
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SOYBEAN SOUTH MARCH 2017
50-50 chance of having PPO resistance in their fields. In addition, Norsworthy’s surveys identified pockets of PPO resistance bordering the Mississippi River to the south. Tennessee also has PPO-resistant populations in more than a half dozen western counties. Altogether, PPO-resistant Palmer amaranth has been confirmed in seven states: Arkansas, Mississippi, Tennessee, the Bootheel of Missouri, Illinois, Kentucky and Indiana. Pat Roberts, who runs Monticello, Ark.based AGvice Crop Consulting with his two sons, says PPO-resistant Palmer amaranth has not been confirmed among his grower clients yet. But he has heard of a few other area growers suspected of having PPO resistance in their fields. “We’re thinking we’re right on the verge of being hit because we have been hammering (Palmer pigweed) pretty hard,” Roberts says. He and his sons already have begun meeting with soybean producers to map out herbicide programs for the 2017 season. Part of that will include multiple modes of action, starting with a residual pre. “We’re trying to get them to run something right before they plant or right behind their planters,” Roberts says. If a grower has grass problems, for example, he says Fierce—a premix of a Group 14 and
Group 15 from Valent U.S.A.—put out just ahead of the planter is one of his go-to products. How to deal with resistance The problem has worsened as growers relied more heavily on PPO herbicides after Palmer amaranth developed widespread resistance to glyphosate, Scott says. “Obviously, the problem is not just the PPO resistance, but there is pigweed resistant to glyphosate, ALS and in some cases, even to the family that includes Prowl and the DNA (dinitroaniline) chemistries,” he says. “This really has the biggest impact on cotton and soybeans, and particularly soybeans, because it leaves us with very limited options. One we are recommending is rotation to corn or rice if possible.” By rotating to a monocot, or grass crop such as corn or rice, producers are able to use different modes of broadleaf herbicides they couldn’t in soybeans. Roberts agrees. “We have guys who have tried rotating corn, and they’ve done a good job (with weed control) in the past.” A rice rotation also brings in water as weed control, since pigweed can’t germinate through flooded fields. But rice producers still have to pay attention to pigweed control on levees and headlands that are above water, Scott says. Outside of crop rotation, growers with SOYBEANSOUTH.COM
glyphosate-resistant Palmer amaranth have two options if they want to stick with herbicide-tolerant crops: LibertyLink and XtendiMax. In cotton, producers are able to use glufosinate and dicamba during the same season on XtendFlex varieties, he says. But soybean producers must decide before planting whether they want to go with glufosinate-tolerant LibertyLink or dicamba-tolerant XtendiMax soybean varieties. Always overlap residuals Regardless of the technology, Scott always recommends starting with clean fields and overlapping residual herbicides beginning with a pre-emerge application. Because some populations of Palmer amaranth have developed resistance to multiple herbicides, he encourages tankmixes with two different modes of action. His recommended pre application is a tankmix of a Group 5, such as metribuzin or atrizine, and a Group 15, such as Outlook, Warrant, Dual or Zidua. Mid-season, growers should return with a tankmix that includes a Group 5. Scott also has been recommending row spacings as narrow as 15 inches because of faster canopy 54280_southads.pdf 2 9/16/16 closure.
Hand rogue stray Palmer pigweed in fields before they go to seed. A single female plant can produce more than 500,000 seeds in a season. UNITED SOYBEAN BOARD
“That way we shade out the ground and prevent late-season emergence of pigweed,” he says. Intensive rotations slow glyphosate resistance In Louisiana, soybean producers are seeing increased glyphosate resistance in Palmer amaranth but not to the extent as in other states, says Ronnie Levy, Louisiana State University AgCenter state soybean specialist in Alexandria. So far, PPO-resistant Palmer pigweed has not been confirmed in the state. “That doesn’t mean we don’t have any,” he says. “We haven’t had the level of problems with (glyphosate) resistant pigweed in 1:22 PM Louisiana, but we’re starting to see more and
more of it in the last couple of years.” Levy attributes the lower amount of resistance to aggressive rotation of crops and modes of action. Depending on the region and the market, soybeans typically are rotated with rice, corn or grain sorghum, or cotton to a lesser extent. LSU AgCenter Extension also urges growers to apply a pre-emerge residual herbicide followed by a post-emerge residual product as part of an integrated weed control program. Where in-season use of glyphosate has lost its effectiveness in Roundup Ready soybeans, Levy says many growers have switched to the LibertyLink system. And he says he expects some growers may consider planting dicamba-tolerant soybeans this season.
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dulaneyseed.com 877-974-7333
Twitter: @SoybeanSouth
MARCH 2017 SOYBEAN SOUTH
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UNIVERSITY OF GEORGIA
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University of Georgia cotton entomologist Phillip Roberts surveys soybeans for kudzu bugs.
Researchers ID beans with natural kudzu bug resistance
responsible for that resistance. First confirmed in Georgia in 2009, kudzu bugs feed on kudzu. But they’ll also jump to other legumes, including soybeans. Since the initial find, kudzu bugs have spread and are now found throughout much of the South and Mid-South.
n EPA registers BASF’s Engenia dicamba herbicide The Environmental Protection Agency has registered Engenia dicamba-only herbicide from BASF Corp. for over-the-top, in-season use on dicamba-tolerant soybeans and cotton. State registrations are pending. Engenia contains a BAPMA form of
dicamba, which is 70 percent less volatile than DGA dicamba, according to a news release. It also targets more than 200 different broadleaf weeds, including those resistant to glyphosate, says Chad Asmus, BASF technical marketing manager, during a recent online news conference. Dicamba belongs to the Weed Science So-
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SOYBEAN SOUTH MARCH 2017
RUSS OTTENS, UNIVERSITY OF GEORGIA; BUGWOOD.ORG
A group of University of Georgia researchers are working to develop soybean varieties resistant to the invasive kudzu bug. Although the pest doesn’t damage soybeans every season, it can cause yield losses of 20 to 60 percent during peak populations. “I think we’re going to have to think of the kudzu bug as a cyclical pest, like the soybean aphid,” Adam Bray, a recent doctoral graduate from the UGA Department of Crop and Soil Sciences, said in a news release. “Populations have died down, but we want to be ready if they do come back.” Working with UGA molecular plant breeder Wayne Parrott, Bray examined 30 Asian land races that Midwest colleagues identified as resistant to soybean aphid. These races were used across Asia, home to the kudzu bug, because of their resilience and productivity. Through field and laboratory testing, Bray narrowed it to two varieties that make it impossible for immature kudzu bugs nymphs to mature. Now the search is on to identify the genes
The kudzu bug, an invasive species native to China and India, has an appetite for legumes, including kudzu and soybeans.
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ciety of America’s Group 4, so BASF recommends incorporating herbicides with other modes of action into weed-control programs. As part of ongoing stewardship efforts, BASF says it plans to train as many applicators, consultants, retailers, Extension and growers as possible through face-to-face meetings and online classes. A handful of Mid-South states, including North Carolina, Georgia, Tennessee, Alabama and Mississippi, have issued 24(c) Special Local Need labels for dicamba and 2,4-Dthat require mandatory applicator training. They also cap wind speed during application at 10 mph compared to 15 mph on the federal label. In late 2016, the EPA registered XtendiMax herbicide with VaporGrip Technology from Monsanto for over-the-top in-season use on dicamba-tolerant cotton and soybeans. The active ingredient is dicamba diglycoamine salt (DGA dicamba) with a proprietary additive to reduce volatility.
n Valent introduces new liquid Valor formulation Valor EZ, a liquid formulation of Valent U.S.A.’s Valor herbicide, will be available for the 2017 season. As a liquid, it provides an easy-to-mix tankmix partner with other residual herbicides for the Roundup Ready Xtend Crop System, according to a news release. No longer will growers have to create a slurry as part of the mixing process. Designed for use on cotton and soybeans, Valor EZ provides residual control of a broad spectrum of weeds—including hard-to-control waterhemp and Palmer amaranth—for four to six weeks. For the first time, Walnut Creek, Calif.-based Valent U.S.A. will offer grower incentives of $6 per acre on qualified purchases when Valor EZ is bought and used in conjunction with the Roundup Ready Xtend Crop System or with PhytoGen Enlist cotton varieties. The herbicide, which contains the active ingredient flumioxazin, belongs to the Weed Science Society of America’s Group 14— PPO inhibitors. SOYBEANSOUTH.COM