Multiple herbicide resistant pigweeds are increasing management challenge to Kansas soybean producers. Declining herbicide options coupled with ever-increasing reports of herbicide-resistant pigweed populations necessitate the evaluation and implementation of alternative ecological-based strategies for pigweed management. This project will focus on understanding the seed retention ability of Palmer amaranth at soybean harvest in Kansas fields and will also determine the efficacy of integrating harvest weed seed destructor (HWSD) technique on Palmer amaranth seedbank dynamics. Information generated through this project will help in developing and integrated weed management (IWM) strategies for mitigating/reducing herbicide resistance in Palmer amaranth populations in Kansas.

1. Determine the Palmer amaranth seed retention at soybean maturity in Kansas.
2. Evaluate the effect of harvest weed seed destructor (HWSD) on Palmer amaranth seedbank dynamics in Kansas soybean fields.

This project will help in quantifying the seed retention ability of Palmer amaranth at soybean harvest in Kansas. This
information is quite important for implementation of harvest weed seed control technologies (including chaff lining and HWSD). Through this project, we will develop IWM-based tactics for weed control that go beyond herbicides and could aid in improving the long-term sustainability and economic viability of Kansas soybean-based cropping systems.

Updated February 14, 2025:
The high retention rate of Palmer amaranth seed on mature, dry female plants observed in this study makes it compelling for Kansas soybean farmers to integrate HWSC technologies into their harvest practices. The use of equipment such as the Seed Destructor or chaff carts can destroy or collect weed seeds during harvest and prevent them from contributing to the weed seedbank. By targeting the 97% of seeds that remain on the plant, HWSD offers an efficient and practical solution for managing multiple herbicide-resistant Palmer amaranth populations. While this study provides valuable insights into seed production and retention, it is limited to fields in Kansas and may not fully represent variability across different regions. Different management practices (herbicide programs, cove crops, etc.) will differently affect seed production. Future studies on this project and others should explore the long-term effects of integrating HWSD strategies on Palmer amaranth seedbank dynamics and soybean yield.

Updated February 14, 2025:
Palmer amaranth is one of the most problematic weeds in U.S. agriculture, particularly in soybean production. Its ability to produce large numbers of seeds, coupled with its resistance to multiple herbicides (Heap, 2024) , has made it a persistent challenge for farmers. Previous research has demonstrated that a female Palmer amaranth plants can produce enormous quantities of seed, with some studies reporting up to 600,000 seeds per plant (Ward et al., 2013) . Seed retention at harvest has been identified as a critical factor in weed seedbank management (Soni et al., 2020).
The management of Palmer amaranth (Amaranthus palmeri) is a challenge in Kansas soybean production, particularly due to its high seed production, persistence in the soil seedbank and herbicide resistance concerns. Harvest Weed Seed Control (HWSD) strategies have shown promise in mitigating this issue by targeting weed seeds during harvest. A field trial assessed the effectiveness of herbicide programs and cover crops on Palmer amaranth biomass and seed production and the effectiveness of the HWSD in reducing Palmer amaranth seed viability in soybean fields. Results indicated that the herbicide programs were not different on their impact on biomass and seed production. In contrast, cover crop use reduced biomass and seed production = 50%. Also, HWSD significantly reduced the viability of Palmer amaranth seeds exiting the back of the combine when the seed control unit was engaged (93% non-viable seed), contributing to a more effective seedbank management.
The integration of HWSD technology into Kansas soybean production may have the potential to significantly reduce Palmer amaranth seed viability. However, this strategy is not a standalone system and should be integrated into an overall integrated weed management program to minimize Palmer amaranth seedbank replenishment and prevent further spread of this problematic weed. This study needs to be replicated in time and space to fully represent the variability across different soil types, climates, or farming practices.

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The management of Palmer amaranth (Amaranthus palmeri) is a challenge in Kansas soybean production, particularly due to its high seed production, persistence in the soil seedbank and herbicide resistance concerns. Harvest Weed Seed Control (HWSD) strategies have shown promise in mitigating this issue by targeting weed seeds during harvest. A field trial assessed the effectiveness of herbicide programs and cover crops on Palmer amaranth biomass and seed production and the effectiveness of the HWSD in reducing Palmer amaranth seed viability in soybean fields. Results indicated that the herbicide programs were not different on their impact on biomass and seed production. In contrast, cover crops use reduced biomass and seed production = 50%. Also, HWSD significantly reduced the viability of Palmer amaranth seeds exiting the back of the combine when the seed control unit was engaged (93% non-viable seed), contributing to a more effective seedbank management.

This project will help in quantifying the seed retention ability of Palmer amaranth at soybean harvest in Kansas. This
information is quite important for implementation of harvest weed seed control technologies (including chaff lining and HWSD). The project will also help in demonstrating soybean producers on the weed seed kill efficacy of Redekop Seed Destructor. If successful, this new IWM tactic can be widely adopted by producers and diverse stakeholders in Kansas, facing the ever-increasing challenges with multiple HR pigweeds.