Date of Award

Spring 5-5-2023

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Plant, Soil, and Environmental Sciences

Advisor

Eric Gallandt

Second Committee Member

Bryan Peterson

Third Committee Member

Mark Hutton

Abstract

Farmers adjust physical weed control (PWC) tools to optimize efficacy based on observations of weeds, the crop, and soil conditions. These many variables make PWC research challenging. To study PWC tool settings more closely, we constructed a soil bin with a mobile tool carriage inside of a heated glasshouse. The soil bin was 2 m wide by 12 m long by 1 m high, with a tool carriage that can operate at 0.4 to 19.0 km h-1. Tool angle, spacing, depth, and speed can all be precisely adjusted from the tool carriage and control panel. The goal of this research was to take the art out of PWC and provide farmers with researched based recommendations, as well as provide researchers with new methods on how to test PWC tools.

The aim of chapter one was to develop methods for a high-throughput system in a controlled environment with artificial weeds (AWs) to test PWC tools. Methods were developed using a simple tine weeder, wooden golf tees as AWs, and a soil bin. The tine weeder was chosen for methods development because it offers uniform soil disturbance and appears to have both uprooting and burial mode of action. Tine speed, angle, and depth were evaluated in both soil bin and field experiments. Tool efficacy from the soil bin were qualitatively compared to efficacy results using surrogate weeds in the field. Results suggest that the simplified conditions of the soil bin system may be useful to test and prioritize tool settings or adjustments for field studies.

Chapter two is about determining whether testing PWC tools in a controlled environment using a soil bin system, reflects treatment effects found in the field. A finger weeder was used and settings of angle, spacing, and speed were tested. The three angles tested were hilling (68o), standard (90o), and scrubbing (108o) with three spacings of 0.6 cm overlap, 0.0 cm fingers touching, and 2.5 cm gap. These angles and spacings were tested in a full factorial design with artificial crops (ACs, 6 mm dia. by 152 mm-long wooden dowels) and AWs (70 mm-long wooden golf tees). Three speeds were tested to represent speeds typical for walking (4 km h-1), tractor cultivating (7 km h-1), and a tractor with a camera guidance system (9 km h-1). Experiments of angle, spacing and speed were replicated in the field. Hilling (68o) caused the greatest efficacy in the soil bin (78%) and in the field (62%). As spacing decreased, efficacy and AC mortality increased in the soil bin, but surprisingly, in the field, there was no difference. In the soil bin, higher speeds of 7 and 9 km h-1 increased efficacy by 77% when compared to 4 km h-1. In the field however, no significant effects were detected between speeds. We conclude that the soil bin is a promising research tool for testing PWC tools.

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