Drone spraying herbicide over a lush bean field.

Bean There, Done That: Optimizing Herbicide Use for Bountiful Bean Harvests

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Elliot Brynn in Climate & Environment August 2025 • 4 min read.

"Balancing Weed Control and Soil Health for Sustainable Bean Production"


Weeds pose a significant challenge to bean cultivation, capable of slashing yields by a staggering 15% to 97%. While herbicides offer a convenient solution for weed management in both annual and perennial crops, their residual effects on subsequent crops (known as carryover) and the rise of herbicide-resistant weeds are creating increasingly complex challenges for farmers.

Among the herbicides commonly recommended for broadleaf weed control in bean crops are fomesafen, imazamox, and bentazon. Farmers often turn to mixtures of active ingredients to broaden the spectrum of weed control, yet it's crucial to carefully consider potential incompatibilities among these mixtures.

This article explores how to strike a balance between effective weed control and minimizing the environmental impact of herbicides. We will discuss the persistence of fomesafen and a formulated mixture of imazamox and bentazon on bean crops, whether used alone or in tank mixtures.

Decoding Herbicide Efficiency: Finding the Right Balance for Bean Crops

Drone spraying herbicide over a lush bean field.

Research was conducted to evaluate the effectiveness of different herbicide treatments on bean crops, assessing their weed control capabilities and any lingering impact on soil health that might affect subsequent sorghum and maize crops. The study scrutinized fomesafen and a commercial blend of bentazon and imazamox, each applied at varying concentrations (25%, 50%, 75%, and 100% of the manufacturer's recommended dosage). These were tested both individually and in tank mixes, alongside weeded and non-weeded control groups.

The findings highlighted a trade-off: while fomesafen (at 250 g ha⁻¹) effectively boosted bean yields, it exhibited considerable persistence in the soil, hindering the growth of sorghum plants even after 183 days. Maize plants also showed signs of herbicide exposure in soil samples taken 153 days post-application, although this didn't significantly affect their overall growth or grain production.

  • Fomesafen: Effective for bean yield but poses carryover risks for sorghum and maize.
  • Bentazon + Imazamox: Inconsistent weed control when used alone.
  • Tank Mixes: Combining fomesafen with bentazon and imazamox can reduce fomesafen dosage while maintaining weed control and lowering carryover risk.
Interestingly, the pre-mixed formulation of bentazon and imazamox struggled to provide consistent weed control throughout the bean growing cycle. However, when fomesafen was added to this mixture, it was possible to reduce the fomesafen concentration by 75% while still achieving excellent weed control. This approach not only facilitated easier bean harvesting conditions but also lessened the risk of herbicide carryover affecting subsequent sorghum and maize crops. Importantly, the persistence of fomesafen in the soil remained unchanged, regardless of whether it was applied alone or as a tank mix with bentazon and imazamox.

Cultivating a Sustainable Future: Responsible Herbicide Use in Bean Farming

The quest for effective weed control in bean cultivation must be balanced with a commitment to environmental stewardship. While herbicides like fomesafen offer powerful solutions, their potential for carryover effects demands careful consideration.

Tank mixing strategies, such as combining reduced doses of fomesafen with bentazon and imazamox, present a promising avenue for minimizing environmental impact without sacrificing weed control efficacy. These tailored approaches require a nuanced understanding of herbicide interactions, soil dynamics, and the specific weed challenges within a given field.

Ultimately, responsible herbicide use in bean farming hinges on informed decision-making, adaptive management, and a holistic perspective that prioritizes both crop productivity and the long-term health of the agroecosystem. Continued research and farmer education will be essential in navigating this delicate balance and fostering sustainable bean production practices.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

Everything You Need To Know

1

How much can weeds impact bean harvests, and what are the primary challenges in managing them?

Weeds can drastically reduce bean yields, anywhere from 15% to 97%. Herbicides offer a convenient solution, but their residual effects on subsequent crops and the development of herbicide-resistant weeds present ongoing challenges for farmers. Managing these challenges is key to successful bean farming.

2

What herbicides are commonly used in bean production, and what should farmers consider when mixing them?

Fomesafen, imazamox, and bentazon are herbicides commonly used for broadleaf weed control in bean crops. Farmers often use mixtures of these to control a wider range of weeds. When combining herbicides, it's crucial to consider potential incompatibilities among them to ensure effective weed control without harming the bean crop.

3

What are the carryover risks associated with using fomesafen on bean crops, particularly for subsequent sorghum and maize crops?

Research indicates that while fomesafen at a rate of 250 g ha⁻¹ effectively increases bean yields, it can persist in the soil long enough to negatively impact subsequent crops like sorghum, and to a lesser extent, maize. This is due to the 'carryover' effect, where the herbicide remains active in the soil and affects the next crop planted.

4

How can tank mixes involving fomesafen, bentazon, and imazamox help in reducing herbicide carryover risks and improving bean harvesting?

Using a tank mix of fomesafen with bentazon and imazamox can allow farmers to reduce the amount of fomesafen needed by up to 75% while still achieving excellent weed control. This approach helps to minimize the risk of fomesafen carryover affecting subsequent crops like sorghum and maize, and it can also lead to easier harvesting conditions for the bean crop.

5

What does responsible herbicide use look like in bean farming, and how can farmers balance weed control with environmental stewardship?

Responsible herbicide use involves carefully balancing the need for effective weed control with the commitment to environmental stewardship. While herbicides such as fomesafen provide powerful solutions, their potential for carryover effects means farmers must consider the impact on subsequent crops and soil health. Using tank mixes and varying herbicide concentrations can help to mitigate these risks and promote sustainable bean farming practices. Further research into alternative weed control methods and the long-term effects of these herbicides is also essential for a sustainable future.

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