Addressing the Weed and Soil Management Trade-offs in Vegetables Through Integrated Cultural and Mechanical Strategies

View the project final report

Commodities

• Vegetables: carrots, cucurbits

Practices

• Pest Management: cultural control, physical control
• Production Systems: organic agriculture

Title:  Addressing Weed and Soil Management Trade-offs in Vegetables Through Integrated Cultural and Mechanical Strategies

Context:  Weed management is a major challenge for vegetable growers. Over-reliance on hand-weeding, herbicides and tillage to manage weeds has contributed to both economic and environmental challenges including herbicide pollution, soil degradation and development of herbicide resistance. By integrating cultural and advanced mechanical weed management strategies, we hypothesized that Midwest vegetable growers could more effectively control weeds while minimizing environmental costs. We also hypothesized that better understanding of the interactions between soil management and mechanical cultivation tools would help growers find an optimal balance between weed and soil management objectives.

Project Objectives: This project had 3 central objectives: 1) Evaluate the benefits of integration of cultural and mechanical weed control in carrots using seed-sizing and in-row mechanical cultivation tools; 2) Explore how soil management practices including historic tillage, compost addition and bed preparation influence the efficacy of  mechanical cultivation in winter squash and 3) Coordinate with growers to test and share best practices.

Approach.  We took advantage of a long-term cropping systems experiment to evaluate interactions between soil management practices (tillage, compost and bed-preparation) and in-row mechanical cultivation efficacy in acorn squash.  We  also conducted field studies to evaluate strategies for integrating cultural and mechanical weed control in carrots, including the effects of seed quality on the efficacy of mechanical cultivation. We used a novel 3D Lidar imaging approach to visualize and analyze soil conditions and their interaction with tools. Our findings were shared with growers through conference presentations, field days and posting on the Physical Weed Control forum website.

Key conclusions. Findings from experiments in carrots (objective 1) reinforced our observations from cultivation testing in other vegetables that at early growth stages hilling is often more efficacious and less damaging to crops than ‘scrubbing’ using a finger weeder. This observation is consistent with our greenhouse evaluations which confirmed that carrots often have a greater height advantage compared to anchorage force advantage relative to weeds (especially grasses) at early growth stages. Hilling also has the advantage that it is easier to accomplish with precision. However, it should be noted that these results may not hold for other crops or later growth stages in carrots. We also observe improved early vigor and a 20% yield advantage of carrots from the largest seed fraction compared to the smallest seed fraction from a single seed lot. Future studies confirming this result across other cultivars and seedlots may provide a simple strategy for improving profitability of carrot production.

Results related to Objective 2 demonstrate the potential impact of soil conditions and cultural practices on cultivation tool efficacy. Historic compost additions improved selectivity of mechanical weed control with either finger weeders or hilling disks at the 2-leaf squash growth stage. We speculate that improved selectivity in compost-treated plots was due at least in part to more vigorous early squash growth, which conferred greater tolerance to physical disturbance. Hypothesized effects of historic soil management on soil surface conditions impacting cultivation tool efficacy were not consistently detected in this study.  Nonetheless, we believe that our approach of using 3-D surface imagery to characterize surface topography is a valuable method for evaluating the impact of previous soil management on cultivation efficacy, as well as the impact of cultivation tools on soils.

Project Outcomes: Knowledge gained from this research was shared with growers at conferences and field days. We believe that growers attending these events gained knowledge to help them integrate cultural and mechanical weed management strategies to reduce the economic and environmental costs of weed management on their farms. Growers have obtained greater understanding of the interaction between cultivation tools and soil conditions to help them optimize their soil and weed management choices for their specific conditions to successfully manage weeds without excessive tillage.

This project had 3 central objectives:

1) Evaluate the benefits of integration of cultural and mechanical weed control in carrots using seed-sizing and in-row mechanical cultivation tools

2) Explore how soil management practices including historic tillage, compost addition and bed preparation influence the efficacy of  mechanical cultivation in winter squash

3) Coordinate with growers to test and share best practices.