Project Details:

Control of Pigweed with an Integrated Systems Approach in Soybean.

Parent Project: This is the first year of this project.
Checkoff Organization:Kansas Soybean Commission
Categories:Weed control, Crop management systems, Sustainability
NCSRP, USB, QSSB Project Code:1780
Project Year:2017
Lead Principal Investigator:Anita Dille (Kansas State University)
Co-Principal Investigators:
Marshall Hay (Kansas State University)
Dallas Peterson (Kansas State University)
Kraig Roozeboom (Kansas State University)
Doug Shoup (Kansas State University)
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Information and Results

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Project Summary

Pigweed is one of the most significant threats to soybean production across the state of Kansas. According to a 2015 survey from the Weed Science Society of America, Palmer amaranth and waterhemp were ranked as the number one and four most troublesome weeds in the nation.
Emergence and growth of pigweed coincides very closely with that of soybean emergence creating an immediate situation for crop and weed competition. In addition to pigweed competition reducing soybean yield, harvest efficiency and equipment maintenance can be greatly impaired. Uncontrolled pigweed also can produce an abundance of seed, greatly impacting weed control costs and effectiveness for many years to come. Thus, it is important to reassess management strategies as well as current economic thresholds for this pest.
During the past three decades, pigweed was effectively managed with multiple over the top applications of ALS-inhibitor and glyphosate herbicides in soybeans. However, widespread resistance of pigweed to both of these classes of herbicides has developed in most soybean cropping systems across the state. Other means of control such as residual herbicides and primary tillage offer opportunities for control but come with challenges. Residual chemistries require timely rainfall for pigweed control – something that can be difficult to achieve in a dryland setting; while heavy, primary tillage can increase susceptibly to drought and increases the potential for soil erosion.
Several new soybean technologies are anticipated from the major agricultural companies that will provide options for pre- and post-emergence herbicide applications for soybeans that were not previously available. Unfortunately, amidst many current setbacks, it is unclear as to when these products will clear the regulatory process and become available to Kansas farmers. Additionally, weed scientists generally agree that even if the new technologies become available, the efficacy and perception of a “silver bullet” that seemed to be the case with glyphosate should not be associated with any of the new technologies.
Row-crop cultivation as an integral, post emerge weed control tool or the use of narrow row width and cover crop residues to increase the shading of the soil to reduce pigweed emergence must be researched. Another effective technology that is widely available is Liberty-Link soybeans. Currently, no herbicide resistance in pigweed to this class of chemistry has been documented. Liberty-Link facilitates an over the top herbicide option for this system.

Project Objectives

Overall objective of experiment: development an integrated approach to effectively manage pigweed in soybean.

1) Evaluate the effect of an integrated systems approach including herbicide, cover crop, row-crop cultivation, and row width in managing pigweed in soybean.

2) Educate soybean producers and agronomy professionals of the outcomes of this experiment to optimize soybean yields and increase grower profitability in terms of pigweed control.

Objective 1: Liberty-Link soybean will be planted in small plot research experiment to assess three row widths, glufosinate plus a residual herbicide program, row-crop cultivation, and a wheat cover crop in the control of pigweed. The entire system will be assessed by including all components as the “kitchen sink” approach followed by the removal each component to understand each component’s contribution to pigweed control. Row-crop cultivation will only be utilized in the widest row width.
The experiment will consist of a total of eighteen treatments across the three row widths of 30-inches, 15-inches, and 7.5-inches. An untreated check will be included in each of the row width treatments to study pigweed emergence in the absence of a treatment. The plots will be arranged in a randomized, split-plot design by row width with four replications of all treatments per site (Table 1)..
Visual percent pigweed control will be assessed for each plot. Digital imagery of the crop canopy will be analyzed in conjunction with soil temperature data to assess treatment’s influence on pigweed emergence. Soil moisture will be assessed to determine the effect of weed control treatments and crop row width on moisture use in the soil profile.
Analysis of data from visual control ratings, crop biomass, grain yield, and crop sensor and soil sensor data will be conducted to determine significant differences in the experiment. Emphasis will be placed on determining the value of each component of the system, such as row width or cover crop, in terms of pigweed control in soybean.

Objective 2: Learning outcomes from the experiment will be communicated to growers at the 2018 Soybean Schools, K-State Field Days, Extension Meetings, and the 2018 Soybean Expo. In communicating with famers, emphasis will be placed on describing the value of each component of the system in regards to pigweed management. By understanding the results of this experiment, Kansas soybean farmers will be better informed about how to make better pigweed management decisions that will increase their farm profitability.

Project Deliverables

1. Understand the effects an integrated systems approach to manage pigweed within a Liberty-Link soybean to facilitate sustainability for soybean growers.

2. Make confident recommendations about the use of narrow soybean row width and cover crops to decrease pigweed emergence and growth.

3. Communicate how the interaction and effect of pigweed control, cover crop, and row width can have implications for profile water management in a potentially moisture-limited environment.

4. Generate applicable extension presentations to communicate the findings of this experiment to soybean producers and agronomy professionals to facilitate pigweed control and thereby increase soybean yield and Kansas grower profitability.

Progress of Work

Update:
Field Status
Sites at Ottawa and Ashland Bottoms Experiment fields have been established are progressing well. Winter wheat cover crop was terminated at anthesis in the beginning of May 2017. Preplant herbicide treatments were applied on May 15, and soybeans were planted on June 1, 2017 with preemergence treatments applied thereafter. Due to crusting, all plots were replanted on June 15 at both sites. Currently both locations have an excellent stand of soybeans. POST applications will be applied in the near future as well as the row-crop cultivation treatment.

Initial Observations
Pigweed pressure is high at both locations with an immediate crop-weed interaction being observed in plots that did not receive a herbicide. Initial observations indicate some suppression of pigweed in those plots that contain winter wheat cover crop residue when compared to those plots that have only bare soil. The value of the pre-plant treatment was also illustrated in the herbicide plots as excellent control was realized at Ashland Bottoms where minimal activating precipitation had occurred after the PRE application, but had occurred for the preplant application.

Crop canopy imagery is also documenting the rapid development of crop canopy in the narrow (7.5”) row spacing when compared to the 30 inch row spacing.

Upcoming Work
In the coming weeks, the row-crop cultivation and POST herbicide treatments will be applied to facilitate the layered residual herbicide program. Visual ratings of weed control and suppression will be taken as well as early and late season weed biomass harvested. Crop canopy imagery will be taken throughout the growing season to maturity.

View uploaded report Word file

Update:
Field Status
Sites at Ottawa and Ashland Bottoms Experiment fields are progressing well and have neared maturity. Both sites received all treatments as required by the experimental plan with observations and biomass harvest samples of both pigweed and crop dried for analysis. Canopy imagery assessment will continue to be taken once a week through harvest to document the potential for new weeds to emerge later in the season.

Initial Observations
The importance of narrow row spacing, cover crop, and a complete herbicide program have been made obvious in the initial findings of this research. In the absence of both a herbicide and cover crop, substantial pigweed pressure has been observed. Pigweed biomass suppression has been observed in both the 15 inch and 7.5 inch rows, whereas maximum pigweed biomass was observed in 30 inch rows. In the absence of herbicide, but with row-crop cultivation and a winter wheat cover crop, approximately 65 to 80% pigweed control has been observed. This is one example of how integrated strategies have been exemplified in this research.

Field Day

On August 16, the annual field day at the East Central Experiment Field was held near Ottawa, KS. The soybean plot was listed on the program and signed as funded by KSC. Unfortunately, the field day was moved indoors due to rain; however, important information learned from the experiment was shared with all present, using pigweed samples and pictures from the field.

Upcoming Work
After the soybeans dry down for maturity, the plots will be harvested and threshed to determine the final yield contribution of each portion of the integrated approach. The data collected will be analyzed and made ready to communicate at extension meetings and the Soybean Expo during the winter months.

View uploaded report Word file

Update:
Field Status
Sites at Ottawa and Ashland Bottoms Experiment Fields have been harvested for yield data. Both sites received all treatments as required by the experiment plan with observations and biomass harvest samples of both pigweed and crop dried for analysis.

Initial Observations
The importance of narrow row spacing, cover crop, and a complete herbicide program have been made obvious in the findings of this research. In the absence of both a herbicide and cover crop, substantial pigweed pressure has been observed. Pigweed biomass suppression has been observed in both the 15 inch and 7.5 inch rows, whereas maximum pigweed biomass was observed in 30 inch rows. In the absence of herbicide with row-crop cultivation and a winter wheat cover crop, approximately 65 to 80% pigweed control has been observed. This is one example of how integrated strategies have been exemplified in this research. Additionally, the addition of a cover crop has demonstrated that pigweed biomass and density can be reduced by approximately 50%.

Field Day
The results from this research was presented at the 2018 Kansas Soybean Expo during the poster session. This event provided producers with a first-hand glimpse at the work we are conducting on integrated weed management. Additionally, the results of this research were present at the Kansas River Valley Irrigators meeting on February 9, 2018.

Upcoming Work
This research will be repeated in 2018 to gain another year of insight into the strategies surrounding integrated pigweed management. We will continue to share the results of our findings in all available venues during 2018. As a result of this research, we plan to publish our results in the scientific journal as well as generate an Extension Publication will color figures to be used in future extension programing when discussing pigweed management.

View uploaded report Word file

Updated April 13, 2018:

View uploaded report Word file

View uploaded report 2 PDF file

Final Project Results

The importance of narrow row spacing, cover crop, and a complete herbicide program were made obvious in the findings of this research. In the absence of both a herbicide and cover crop, substantial pigweed pressure was observed. Pigweed biomass suppression was observed in both the 15 inch and 7.5 inch rows, whereas maximum pigweed biomass was observed in 30 inch rows. In the absence of herbicide but with row-crop cultivation and a winter wheat cover crop, approximately 65 to 80% pigweed control was observed. This is one example of how integrated weed management strategies were exemplified in this research. Additionally, the addition of a cover crop demonstrated that pigweed biomass and density can be reduced by approximately 50%.

Benefit to Soybean Farmers

Kansas’ soybean farmers must implement all available tactics to manage this weed in an integrated systems approach, because of the enormity of the pigweed challenge in soybeans and the lack of an obvious solution. This system will be critical to the sustainability of soybean production in Kansas through the adoption of a zero-tolerance policy for pigweed presence in fields.

The overall objective of this study is to evaluate an integrated systems approach of using row-crop cultivation, reduced row width, cover crops, and glufosinate with residual herbicides to build and communicate a means for Kansas’ soybean farmers to implement sustainable pigweed control.

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