Mechanical cultivation is important for managing weeds in vegetables, but it can damage crops through uprooting or burial. We evaluated approaches to improve efficacy and selectivity of mechanical cultivation, and the impact of soil management practices on tool efficacy. Chapter 1 reports on experiments that test the effects of long-term reduced tillage and compost additions, as well as previous cultivation tool, on soil surface conditions, cultivation tool efficacy and yield in winter squash. Compost addition had variable effects on soil conditions and efficacy between the two years, but increased squash mid-season biomass in both years and squash yield in one of two years. Surprisingly, reduced tillage had no detectable effect on soil surface conditions, cultivation efficacy, or yield. In one year, hilling at the first event improved finger-weeding efficacy at later cultivation events. Chapter 2 reports on field experiments evaluating the effects of carrot seed size and cultivation tool on cultivation efficacy and crop yield. We tested if larger seed sizes could increase carrot anchorage force and height at the time of cultivation and increase tolerance to cultivation. We found that 1) carrots from large seeds had higher anchorage force and height at time of cultivation, 2) tool effects varied by year and in one year large seeds increased cultivation tolerance, 3) yields were 20% higher from larger seeds. Chapter 3 presents a model to provide insight into the effects of crop and weed characteristics on selectivity of cultivation tools that uproot or bury weeds. The model was parameterized using anchorage force and height data from carrots and five weed species grown in a greenhouse, and predicts the effects of cultural practices influencing the relative size of carrots and weeds. It suggests that selective potential in carrots varies with crop growth stage and weed species, but is generally higher for tools that bury weeds than for those that uproot. The model demonstrates the impact of cultural practices including stale seedbedding and seed size selection on selective potential.
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