The grant will involve more than a half dozen crop protection companies and their recommended programs. This study will also involve Southwest Minnesota State University (SMSU) as a supplemental trial. The grant will be comprehensive in the matter of residual herbicide waterhemp control and soybean injury through and objectives achieved through FIVE related and relevant sub-studies:
1) a large trial industry-wide treatment demonstration [at research farm],
2) small trial industry treatment demonstration [at SMSU]
3) micro-rate combination efficacy and soybean injury in PPO susceptible varieties [at research farm], and
4) PRE vs. PRE fb EPOST micro-rate combination efficacy [at research farm].
Study 1. “Large Industry Standard” will be a summation of the best treatments from MSRPC funded research in 2016, 2018, 2019, and 2020. These 40 treatments by 4 replications [randomized complete block design] will all be options for farmer use with treatment cost and efficacy data provided at field day. Ideally, all our industry partners will be present for one-on-one discussions with farmers post-MSRPC trial tours.
Study 2. “Small Industry Standard” will be a sub-set of study (1) treatments and located at SMSU research farm. SMSU will furnish the land, Next Gen Ag will conduct all other activities and be invited to participate in any field days. These 14 treatments by 4 replications [randomized complete block design] will be options for farmer use with treatment cost and efficacy data provided.
Study 3. “Soybean Varietal Sensitivity to Variable Micro-Rate Champion Rates” will achieve three goals. 1) PPO susceptible soybean variety screening, 2) soybean crop injury, and 3) rate ratio screening of the micro-rate combination champion treatment [PRE ONLY: Valor SX @ 2oz + Warrant @ 40floz + Blanket @ 8floz + Flexstar @ 10floz]. These 8 herbicide treatments and 8 soybean varieties [randomized complete block design in a split-plot arrangement] will provide data on the safety of the 2020 micro-rate combination champion in susceptible soybeans as well as determine the optimal ratio of chemical to achieve 90% waterhemp control 75 DAA. The parent treatment from 2020 being evaluated achieved 92% season long control with a PRE only application timing. Trial will be included on field day.
Study 4. “PRE vs. PRE fb EPOST at Variable Micro-Rate Champion Rates” will observe the 2020 micro-rate combination champion treatment [PRE ONLY: Valor SX @ 2oz + Warrant @ 40floz + Blanket @ 8floz + Flexstar @ 10floz] against itself with the exception of manipulating timings. The PRE only treatment will be compared to itself as a PRE fb EPOST break out of the 4 components within label restrictions and at various rates. These 20 treatments by 4 replications [randomized complete block design] well determine the optimal rates and timings of the 2020 micro-rate combination champion treatment components. Data will be compared with study (3) data as well with check treatment rates and applications. Trial will be included on field day.
Literature Review
Resistant waterhemp populations are common across Minnesota crop production regions. Eighty percent of Minnesota sugarbeet growers representing 13 counties reported waterhemp as the most troublesome weed in a 2015 survey (Lueck et al. 2015). Renville County, where the research will be conducted, ranked 3rd in soybean production in 2016 and was inclusive of the 13 counties represented in the survey. Waterhemp not controlled significantly reduces yield in soybean by 43-46% (Hagar et al. 2002, Legleiter et al. 2009).
Growers have been faced with low commodity prices lately, so maintaining soybean yield potential is critical. Soybean yield and stand can also be impacted by herbicide applications. No prior publications could be found related to extensive pre-emergent residual herbicide screening and soybean crop injury, however, experience and grower conversations indicate concern related to products such as sulfentrazone, flumioxazin, and metribuzin.
Combining safe and economical applications will provide the greatest value added to the grower. Ninety percent waterhemp control 75 DAA is attainable while maintaining a competitive cost per acre value (Lueck and Peters 2016, Lueck 2018). Additional modes of action annually can reduce selection pressure on rapidly adaptive weed populations, specifically waterhemp. Micro-rate programs in sugarbeet combined crop safety with weed control (Dexter, Luecke, Bredhoeft 1997). Micro-rate programs decreased crop injury by 27% while maintaining weed control of five economically significant species in sugarbeet. Palmar Amaranth is a “super” weed appearing more regularly in Minnesota the past two years despite efforts to eradicate. Waterhemp and palmer amaranth belong to the same biological family, and similar herbicide programs may be considered to control both species. The most susceptible growth stage for plants is emergence and to ensure herbicide activity in the soil at weed emergence is critical to limiting resistance development and effective weed control.
Materials and Methods
A known ALS and EPSP resistant waterhemp population will be tested near Renville (Lueck 2019). Conventional tillage on Webster Clay-Loam soil. Soybean will be seeded at 140,000 plants per acre on 30” row spacings. The five studies will have various plot sizes and application timings. Small plot herbicide applications will be done utilizing a bike sprayer with a 4-nozzle, 20-inch spaced boom while large plot application will be done utilizing an 8-row tractor sprayer with a 12-nozzle, 20-inch spaced boom. All treatments will be applied through 110002 AIXR nozzles at 15 GPA.
Specifics of each study and treatment list below:
Study 1. “Large Industry Standard” is a randomized complete block design across 40 treatments and 4 replications. Location will be Renville, MN, research farm only. Plot area is 2.00 acres including winter wheat buffers. Treatments applied utilizing small plot bike sprayer. Products target a PRE and V1-V2 application timing in a two-pass residual herbicide system. A majority of treatments will include conventional herbicides only and be sprayed with clethodim to control volunteer corn and grasses, while a sub-set of treatments will include glyphosate EPOST for grass control and minimal waterhemp control in a EPSP resistant population. Data to be collected are waterhemp control at 15, 30, 45, 60, and 75 DAA (days after application “A”). Yield will not be taken in this study. Trial collaboration with 7 major industry partners. A plot tour will be held.
Study 2. “Small Industry Standard” is a randomized complete block design across 14 treatments and 4 replications. Location will be SMSU campus research farm only. Plot area is 0.75 acres including alley buffers. Treatments applied utilizing small plot bike sprayer. Products target a PRE and V1-V2 application timing in a two-pass residual herbicide system. A majority of treatments will include conventional herbicides only and be sprayed with clethodim to control volunteer corn and grasses. Data to be collected are waterhemp control at 15, 30, 45, 60, and 75 DAA (days after application “A”). Yield will not be taken in this study. Trial collaboration with 7 major industry partners and SMSU agronomy department. A SMSU sponsored plot tour will be held.
Study 3. “Soybean Varietal Sensitivity to Variable Micro-Rate Champion Rates” is a randomized complete block design with split-plot arrangement with 8 soybean varieties and 8 herbicide rates (64 total 10 ft x 10 ft plots) across 4 replications. Location will be Renville, MN, research farm only. Plot area is 1.75 acres including winter wheat buffers. Products target a PRE application timing only in a one-pass residual herbicide system. Soybean varieties will include PPO susceptible genetics. Data to be collected are waterhemp control and soybean crop injury at 15, 30, 45, 60, and 75 DAA (days after application “A”). Due to reduced rate ratio and PRE only system, yield data is unlikely to be relevant due to the impact of late season waterhemp competition in soybean. Yield will not be taken. A plot tour will be held.
Study 4. “PRE vs. PRE fb EPOST at Variable Micro-Rate Champion Rates” is a randomized complete block design across 20 treatments and 4 replications (Table 4). Location will be Renville, MN, research farm only. Plot area is 1.10 acres including winter wheat buffers. Products target a PRE and V1-V2 application timing in a two-pass residual herbicide system. Treatments will include conventional herbicides only and be sprayed with clethodim to control volunteer corn and grasses. Data to be collected are waterhemp control at 15, 30, 45, 60, and 75 DAA (days after application “A”). Yield will not be taken in this study. A plot tour will be held.