Date of Award

2008

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Plant, Soil, and Environmental Sciences

Advisor

Mark Hutton

Second Committee Member

David Handley

Third Committee Member

Eric Gallandt

Abstract

Vegetable growers and consumers are becoming more interested in sustainable agricultural practices. For many the goal is to minimize the need for expensive herbicides and/or tillage. The challenge is to accomplish these goals without sacrificing yields and long term farm vitality. Hybrid mulch and fall made bed systems which aim to minimize both tillage and herbicides were evaluated from 2004 to 2007 in Monmouth, Maine, to determine their effects on yield, economics, soil quality, and weeds. In 2006 and 2007 the systems were also evaluated on-farm with three Maine growers. The hybrid mulch system used raised, plastic mulched beds which remained in place for three cropping seasons with a living mulch inter-bed of perennial ryegrass {Lolium perenne L.) and white clover {Trifolium repens L.). Two crop rotation orders of tomatoes, cucumbers, and pumpkins were planted into the system to evaluate its impact on yield and economics. Traditional spring-made beds with bare ground inter-beds were used as a basis for comparison. Rotation 1 (TCP) was tomatoes in 2005, followed by cucumbers in 2006, and pumpkins in 2007. Rotation 2 (CTP) was cucumbers, tomatoes and then pumpkins. Compared to traditional plots both hybrid mulch rotations produced either greater or similar yields in 2005 and 2006 when they led to earlier planting dates, and lower yields in 2007 when they did not. Partial budgets showed net returns of the hybrid mulch TCP rotation were greater than those of the traditional rotation while the CTP rotation produced similar net returns in both systems. The fall bed system was similar to the hybrid mulch system except the beds remained in place only through one cropping season. The beds were established in fall 2005, this time with winter rye (Secale cereale L.) replacing the perennial ryegrass. The objective was to assess impacts of the system on soil quality and the germinable weed seedbank. In the spring and summer of 2006 the inter-beds were managed either by mowing, or by killing the cover crop with herbicides prior to planting and leaving the dry residue mulch in place. Traditional plots were established in the spring of 2006. The fall bed system did not influence soil quality in the short time frame of this experiment. The density of germinable weed seeds in the weed seedbank started out high and increased over the course of the experiment. Weed species composition changed only slightly, with the density of the annual redroot pigweed {Amaranthus retroflexus) increasing in traditional compared to fall beds. On farm evaluations of hybrid mulch and fall bed systems with three Maine growers showed yield reductions with the living mulch, and therefore the growers agreed the fall beds with straw mulch were the most interesting for further research. While the two systems did not influence soil quality or control weeds, the hybrid mulch system did maintain or improve yields and net returns in years when it allowed earlier spring planting. Thus, the system has the most potential for growers in Maine when it is used as a season extender.

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