Tuesday September 03 Ag News

 Does Narrow Row Spacing Help Suppress Weeds and Increase Yields in Corn and Soybean?
Amit Jhala - Professor and Associate Department Head, Department of Agronomy and Horticulture

Narrow row spacing holds the potential to help suppress weeds and increase crop yield. Over the past two decades, there has been a growing interest in row spacing narrower than 30 inches, particularly in soybean. For instance, in Nebraska, the average row width of soybean decreased from 28.5 inches in 1993 to 24.0 inches in 2003 and 24.2 inches in 2023 (USDA NASS 1993, 2003, 2023). For corn, while the average row spacing in Nebraska remained relatively stable (33.4 inches in 1993, 32.2 inches in 2003, and 30.8 inches in 2023), there has been a shift in its distribution. The percentage of corn rows that are 30.5 inches or less has increased from 34.5% in 1993 to 52.6% in 2003 and 68.3% in 2023 (USDA NASS 1993, 2003, 2023).

Many studies in the United States have researched the potential of narrow rows (<30 inches) in suppressing weeds and/or increasing corn and soybean yields. However, no systematic and quantitative synthesis exists for these studies. We compiled results from individual studies using meta-analysis (Singh et al. 2023). Meta-analysis is a statistical technique to compile and analyze results from multiple independent studies to provide more reliable and comprehensive conclusions on any specific research topic or question. Studies fulfilling the following pre-determined criterion were included in the meta-analysis:
    Corn or soybean field study from the United States.
    Row spacing treatments of 30 inches (control) and under (<30 inches).
    Have reported means of control (30 inches) and row spacing treatments (<30 inches) for at least one response variable (weed density, weed biomass, weed control, weed seed production, and corn/soybean yield).

A total of 35 studies conducted between 1961 and 2018 fitted this criterion. We compiled 1,904 pair-wise observations from these relevant studies. Most studies investigated soybean (n = 27 out of 35) and were conducted in the midwestern United States (Figure 1; n = 29 out of 35).

What Did We Find?
    Row spacing less than 30 inches suppressed weed density and biomass by ≥34% and weed seed production by 45%, while increasing weed control by 32% and crop yield by 11% compared with 30-inch rows (Figure 2).
    The benefits of narrow rows were observed in soybean but not in corn. In soybean, less than 30-inch row spacing suppressed weed density and biomass by ≥42% and improved yield by 12% compared with 30-inch row spacing.
    Crop yield was not improved in weed-free plots and had the most significant increase when plots were untreated. This indicates that crop yield was partially enhanced due to the weed suppression effect of narrow row spacing, among other factors.
    Greater suppression in weed biomass and weed seed production was observed when sequential application of herbicides was used instead of single application in addition to narrow rows.

What Were the Results of Studies Conducted in Nebraska?
    Seven studies were conducted in Nebraska that were included in the meta-analysis (Burnside 1979; Burnside and Colville 1964; Hock et al. 2005, 2006; Knezevic et al. 2003; McDonald et al. 2021; Moomaw and Martin 1984). All studies included soybean except one with corn (Moomaw and Martin 1984).

    The earliest study was conducted in 1961 and 1962 in Lincoln, where researchers evaluated the effects of row spacing, tillage, irrigation, and pre-emergence applications of 3-amino-2,5-di-chlorobenzoic acid (amiben) on weed suppression and soybean yield (Burnside and Colville 1964). The soybean was planted at a 90 lb/ac seeding rate in 10-, 20-, 30- and 40-inch rows. Researchers reported an average weed biomass reduction of 39% in 10- and 20-inch (170 lb/ac) soybean rows compared with 30-inch rows (280 lb/ac). The likely reason for weed suppression was early canopy closure in narrow rows. In 1962, soybean in 10- and 20-inch rows shaded the ground completely 22 and 11 days before soybean in the 30-inch rows (58 days after planting), respectively. They also reported an average yield increase of 32% in 10-inch rows (41.4 bu/ac) and 11% in 20-inch rows (35.0 bu/ac) compared with 30-inch rows (31.4 bu/ac).

    Another study was conducted in Lincoln from 1973 to 1975 where two soybean varieties were planted in 15- and 30-inch rows under non-irrigated conditions (Burnside 1979). Weeds were either not removed or removed at weekly intervals of 0-2, 2-3, 2-4, 2-5, 2-6, 2-9, 4-9, and 6-9 weeks after soybean planting. When weeds were not removed, average weed biomass was slightly lower in 15-inch (2,226 lb/ac) compared with 30-inch rows (2,329 lb/ac). As a result, soybean yield was somewhat higher in 15-inch (12 bu/ac) than 30-inch (11 bu/ac) rows, but the difference was statistically similar.

    One study addressing the critical time for weed removal was conducted from 1999 to 2001 at Eastern Nebraska Research, Extension and Education Center near Mead, and in 2000 and 2001 at the Haskell Agricultural Laboratory near Concord (Knezevic et al. 2003). The soybean was planted at 168,000 seeds/ac in 7.5-, 15-, and 30-inch rows. The critical time of weed removal was consistently delayed with the narrowing of rows in all site years; it occurred at the first trifoliate stage for 30-inch row spacing, at the second trifoliate stage for 15-inch row spacing, and at the third trifoliate stage for 7.5-inch row spacing. Therefore, soybean planted in wider rows required weed management early in the season due to reduced early-season crop tolerance to weeds. This study reported lower soybean yields with increased row spacing in season-long weedy conditions in four out of five site years. Still, yield response to row spacing was generally inconsistent under season-long weed-free conditions, indicating that soybean yield increase in 7.5-inch rows was probably due to improved crop competitiveness against weeds.

    Two studies were conducted in 2002 and 2003 in northeastern Nebraska at the Haskell Agricultural Laboratory near Concord, and in 2003 at the University of Nebraska Agricultural Research Farm in Lincoln (Hock et al. 2005, 2006). The soybean was planted at 163,000 to 164,000 seeds/ac in 7.5- and 30-inch rows. Ten common weed species were seeded three times at soybean planting, emergence and the first trifoliate leaf stage. In general, lower leaf area and biomass were produced by most weed species in 7.5-inch rows compared with 30-inch rows. For example, averaged across the time of emergence, velvetleaf produced 40% lower leaf area (1,113 vs. 1,870 cm2/plant), and sunflower produced 27% lower biomass (275 vs. 375 g/plant) in 7.5-inch rows compared with 30-inch rows. This generally corresponded to lower soybean yield loss in 7.5-inch than 30-inch rows; however, some weed species, such as common cocklebur and giant ragweed, caused similar yield loss in both row spacing.

    The most recent study was conducted in 2018 and 2019 in a grower’s field near Carleton, Nebraska, to assess the effect of row spacing and herbicide programs for managing glyphosate-resistant Palmer amaranth in XtendFlex (dicamba/glufosinate/glyphosate-resistant) soybean (McDonald et al. 2021). The soybean was planted at 140,000 seeds/ac in 15- and 30-inch rows under rainfed conditions. Fourteen herbicide programs were evaluated: two early-POST, four early-POST fb late-POST, four PRE fb early-POST, and four PRE fb early-POST plus a residual herbicide. PRE fb early-POST programs, including residual herbicide, were the most effective in controlling Palmer amaranth. However, control was mostly similar across the row spacings. Averaged across herbicide programs, the lower density of Palmer amaranth was reported under 15 inches (4,047 plants/ac) than 30 inches (60,702 plants/ac) row spacing, resulting in a 15% increase in soybean yield under 15 inches (27 bu/ac) than 30 inches (23 bu/ac) row spacing in one year in 2019.

Take Home Messages
    Row spacing less than 30 inches (such as 20 or 15 inches) could be integrated with herbicides to help suppress herbicide-resistant weeds that may provide a yield advantage in soybean.

    Results of the meta-analysis and studies conducted in Nebraska suggest that narrow rows (<30 inches) may suppress weed density and biomass, delay their critical time of removal, and positively impact soybean yield. However, this response varies yearly. Also, the adoption and success of narrow rows are governed by complex interactions of important factors such as crop variety, geographic location, equipment costs, the occurrence of diseases like Sclerotinia stem rot, planting time, relative time of weed emergence, seeding rate, and soil moisture availability, etc. that need to be considered for deciding to adopt narrow rows at farm-level.

    For corn, narrow row spacing did not lead to weed suppression or yield advantage across the limited studies included in this meta-analysis.



Iowa Farm Bureau, Iowa Athletics launch America Needs Farmers (ANF) contest, name Brandon Myers as new ANF Wall of Honoree

With football season on the horizon, Iowa Farm Bureau and University of Iowa Athletics are once again teaming up to celebrate why America Needs Farmers through the ANF Game Day Experience -- a chance to win four tickets and on-field sideline access to the ANF game on Oct. 12 against the University of Washington.

For a chance to win, go to IowaFarmBureau.com/ANFExperience and take a short, multiple-choice quiz to learn how Iowa farmers provide high-quality food while caring for the environment and their animals. The prize package also includes a Kirk Ferentz-autographed football and ANF gear. The contest runs through Oct. 2.
Brandon Myers Named 2024 ANF Wall of Honoree

The ANF Wall of Honor salutes past University of Iowa football players who exemplify the tenacity, work ethic and character of the Iowa farmer, and former Hawkeye standout and NFL star, Brandon Myers, becomes the 12th member of the prestigious group.

A four-year letter winner with the Hawkeyes, Myers credits his success to a solid work ethic and lessons learned growing up on his grandparents’ farm in central Iowa. Myers utilized his farm strong work ethic to capture three bowl game victories with the Hawkeyes followed by a successful eight-year NFL career.

“Growing up and spending time on my grandparents’ farm helped instill a work ethic and grit I have carried with me through my life, and it’s something I share with my boys,” Myers says. “That means constantly showing up, doing things the right way and putting in hard work whether on the farm or the football field.”

Previous ANF Wall of Honor recipients include Casey Wiegmann (2012), Jared DeVries (2013), Bruce Nelson (2014), Robert Gallery (2015), Dallas Clark (2016), Chad Greenway (2017), Aaron Kampman (2018), Matt Kroul (2019), Marshal Yanda (2021), Tony Moeaki (2022) and Bryan Bulaga (2023).     

America Needs Farmers was launched by former Hawkeye Coach Hayden Fry to show support for farmers during the 1980s Farm Crisis by placing a gold ANF decal on players’ helmets. This year marks the 39th anniversary of ANF and its longstanding tribute to America’s farmers. In this same spirit, the ANF game recognizes the hardworking men and women in agriculture whose work creates a positive impact in Iowa and across the globe.

“Farming and football have each evolved since the inception of ANF during the 1980s, but the values and qualities that define ANF are just as important and remain true today -- commitment, integrity and the drive to continuously improve upon their craft,” says Brent Johnson, Iowa Farm Bureau president. “We look forward to welcoming fans to the ANF Legends Tent on ANF Game Day to celebrate the importance of agriculture in our lives and recognizing Brandon Myers as the Wall of Honoree.”  

During ANF Game Day, Iowa Farm Bureau will be present at the ANF Legends Tent at Krause Family Plaza where fans can interact with local farmers, win prizes and get autographs from former Hawkeye greats, including this year’s ANF Wall of Honoree, Brandon Myers. ANF merchandise will also be for sale in ANF Plaza with a portion of the proceeds benefiting the Iowa Food Bank Association. For more information, visit AmericaNeedsFarmers.org.



Iowa fertilizer plant sold to Koch for $3.6B

Koch Ag & Energy Solutions, LLC (KAES), a leader in agriculture, energy, and chemical markets, has successfully acquired OCI Global's fertilizer plant in Wever, Iowa, for $3.6 billion.

The acquisition, announced on December 18, 2023, provides KAES with ownership of a state-of-the-art facility that significantly boosts its production capacity and market reach.

The Wever facility, which opened in 2017, has the capability to produce 3.5 million metric tons of nitrogen fertilizers and diesel exhaust fluid annually.

This addition complements KAES's existing operations, which include four nitrogen production facilities in the U.S., one in Canada, and an extensive terminal network. The company also has stakes in three nitrogen facilities in Trinidad and Tobago and a phosphate production facility in Morocco.

Mark Luetters, president of Koch Ag & Energy Solutions, highlighted the importance of this acquisition, stating, "This acquisition marks another significant investment in the growth of our fertilizer business. Over the past 15 years, we have invested $2 billion in our North American production facilities to enhance reliability, expand production, and improve logistics for our customers. This investment enhances our ability to serve customers long-term by providing additional flexibility to adapt to their nitrogen preferences."

The strategic location of the Wever facility will allow Koch Fertilizer to extend its product offerings to new customers in the eastern U.S. while providing expanded products and services to existing customers.

"We are excited about the opportunities the Wever facility provides to better serve existing and new customers," said Scott McGinn, executive vice president of Koch Fertilizer.

In addition to the production capacity, the acquisition brings approximately 300 new employees to the Koch Fertilizer family.

Pascal Van Teeffelen, KAES executive vice president of operations and compliance, expressed confidence in the new team, stating, "We are impressed with the employees and look forward to working with the team to maintain safe and reliable operations while exploring opportunities to grow production in the future."

Barclays served as the exclusive financial advisor to KAES for this transaction, with Jones Day acting as the legal advisor. This acquisition marks a significant milestone for KAES, reinforcing its commitment to growth and customer satisfaction in the fertilizer industry.



H5N1 Cases Possible in California

The highly pathogenic avian influenza virus affecting dairy herds around the country may have landed in California's Central Valley as the California Department of Food and Agriculture (CDFA) is investigating a possible outbreak at three dairy farms.

CDFA late Thursday announced the testing of samples from three dairies at the state's laboratory. Any positive tests at the California lab would be considered "presumptive" and submitted to USDA for final test confirmation.

California is the country's largest milk-producing state with more than 1.7 million milking cows and more than 1,300 dairies, according to USDA. The state produced about 20% of the U.S. milk supply.

While confirmed cases of the H5N1 virus in dairy cattle have slowed down, there have been 20 confirmed herd outbreaks over the past 30 days in five states, including 13 herds infected in Colorado alone. The latest confirmed case was reported in a Michigan herd on Aug. 26.

State and federal officials have stressed since the outbreak began in early spring that pasteurization is fully effective in deactivating the virus. There are no health concerns for dairy products that have been pasteurized. Still, USDA requires milk from impacted cows to be diverted from the food supply and destroyed.

Since late March, USDA has confirmed infected dairy cattle in 193 farms across 13 states.