Project Details:

Title:
Control of Pigweed with an Integrated Systems Approach in Soybean

Parent Project: Control of Pigweed with an Integrated Systems Approach in Soybean
Checkoff Organization:Kansas Soybean Commission
Categories:Weed control, Crop management systems, Sustainability
NCSRP, USB, QSSB Project Code:1880
Project Year:2018
Lead Principal Investigator:Anita Dille (Kansas State University)
Co-Principal Investigators:
Keywords:

Contributing Organizations

Funding Institutions

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 susceptibility 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. Weed scientists generally agree that even as 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 are two methods that 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.
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.

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 spacing 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.

PROCEDURES

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 16 reatments across the three row widths of 30-inches, 15-inches, and 7.5-inches. The plots will be arranged in a randomized complete block design by row width with four replications of all treatments per site.
Visual percent pigweed control will be assessed for each plot. Digital imagery of the crop canopy will be analyzed throughout the season to understand in influence of canopy development on pigweed emergence.
Analysis of data from visual control ratings, crop biomass, grain yield, and imagery 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 2019 Soybean Expo. In communicating with farmers, 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 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 spacing 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.


Project Deliverables

Expected outcomes from this research project:
1. Understand the effects an integrated systems approach to manage pigweed in 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. 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

Updated June 22, 2018:
Second year of field studies have been established at three locations across eastern KS. Please see report in attached file.

View uploaded report Word file

Updated September 10, 2018:
Second year of field studies established and progressing well at three locations across eastern KS. Please see report in attached file

View uploaded report Word file

Updated December 11, 2018:
Yield data from the field experiments is coming in, with two of three sites awaiting drier harvest weather. See attached report for additional details.

View uploaded report Word file

Updated April 15, 2019:
All field trials have been completed. See attached report for details. One Extension publication is near final publication and is attached (MF3448 Pigweed).

View uploaded report Word file

View uploaded report 2 PDF file

Final Project Results

All treatments containing the herbicide program component resulted in excellent (> 97%) pigweed control which demonstrates the importance of using overlapping residual herbicides with multiple effective sites of action. Treatments containing row-crop cultivation (RC) tended to reduce pigweed density and biomass at 3 and 8 weeks after planting (WAP) in all locations compared to the 30-inch row width no cover crop treatment. Mixed results were observed when the effect of winter wheat cover crop (CC) was considered: in about half of the site-years, CC provided approximately 50% reductions in pigweed density and biomass whereas in the remainder CC provided no change to an increase in pigweed density. Decreased row widths achieved the most consistent results by reducing pigweed biomass at 8 WAP when data were pooled across location: decreasing row widths from 30-inches to 15-inches resulted in a 23% reduction whereas decreasing from 15-inches to 7.5-inches achieved a 15% reduction. In conclusion, RC should be incorporated where possible as a mechanical option to manage pigweed, and decreased row widths should be used when economically feasible to suppress late season pigweed growth. CC achieved inconsistent pigweed control in this research and should be given special consideration prior to implementation. The integral use of these components with an herbicide program as a system should be recommended to achieve the best pigweed control as well as reduce the risk of resistance.

Benefit to Soybean Farmers

Because of the enormity of the pigweed challenge in soybeans and the lack of an obvious solution, Kansas’ farmers must implement all available tactics to manage this weed in an integrated systems approach. 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.
First year results indicated that there was value in cultural weed control methods, such as row-crop cultivation, narrow row spacing, and use of high-residue cover crops for weed suppression. Narrow row spacing (<15-inches) resulted in at least 18% pigweed control compared to none with 30-inch rows. No individual cultural control method resulted in excellent pigweed control, but the integrated use of multiple methods with a complete herbicide program can result in excellent pigweed control while managing the issue of herbicide resistance.

Performance Metrics

Project Years