Cover Crops and Strip-tillage Influence on Soil Health and Food Safety in a Midwest Muskmelon Production System

Cucurbit growers in the North Central region face several critical challenges including increases in extreme rainfall events, increased soil erosion, decreased soil quality, and increased risks of fruit contamination with soil-borne plant and human pathogens. For example, recent outbreaks associated with foodborne illness threatened livelihood of melon growers, with Listeria monocytogenes and Salmonella killing consumers throughout the United States. Muskmelons (Cucumis melo L.) are a potential food safety concern for several reasons:  the fruit is in contact with the soil throughout the growing season, the heavily textured surface of the rind is a challenge to sanitize, and the flesh is favorable for bacterial growth due to its moderate pH and high nutrient content.     Adoption of reduced tillage practices, coupled with cover crop residues may help buffer cucurbits from rainfall extremes, suppress weeds, improve soil quality and health, and also reduce growth and dispersal of both human and plant pathogens. This study, conducted at the Horticulture Research Station, Ames, IA, investigated muskmelon (cv Aphrodite) production using three different cover cropping systems, cereal rye (Secale cereale L. ‘Wheeler’), cereal rye-hairy vetch (Vicia villosa ‘Purple Bounty’) mixture, and no cover crop, either conventionally tilled or strip-tilled after the cover crop was roller-crimped.  The field was inoculated with Listeria innocua, a non-pathogenic species, and its presence was determined in the soil, on cover crop residue and on the exterior of fruit during the growing season.  Conventional tillage showed the highest yield for marketable fruits.  Conventional tillage treatment also increased soil NO₃-N concentration and EC. Strip tillage treatment suppressed the biomass and density of broadleaf and grass weeds in the between row area.  Treatments had no significant effect on estimation of leaf chlorophyll (SPAD) or vine length.  Both rye and rye-vetch eliminated populations of Listeria innocua in the soil, while no cover crop showed only a slight decrease. Listeria innocua was detected on rye cover crop residue at harvest.