Effects of cover crops and tillage in a muskmelon production system

Abstract

<p>Most muskmelon (Cucumis melo L.) production in the upper Midwest relies on intensive tillage and plasticulture. An alternative system starts with the use of a roller-crimper to terminate winter cover crops, thus forming a thick organic mulch. Then, all tillage performed is restricted to a narrow strip in which muskmelons are transplanted. Cover crops and strip-tillage can increase soil health, suppress weeds, and improve net profitability. Muskmelons are an important crop for vegetable growers and are among the top consumed produce items in the U.S. Foodborne illness outbreaks of Salmonella and Listeria monocytogenes associated with muskmelon consumption have resulted in consumer fatalities, and negatively impacted the livelihood of producers.</p> <p>A study was carried out over two seasons (2014-15 and 2015-16) to assess the effect of cover crops and tillage on the performance of muskmelon production. Data was collected on cover crop growth, soil temperature, soil moisture, weed biomass, the concentration of nitrate-nitrogen in leachate, soil nutrient concentrations, muskmelon plant growth, soil microbial biomass carbon, soil microbial functional diversity, muskmelon yield, net profitability, and fruit quality. Our goal was to take a comprehensive view of the differences between the use of cover crops [no cover, cereal rye (Secale cereale L.), and cereal rye-hairy vetch (Vicia villosa Roth)] with conventional tillage and strip-tillage. We also assessed how treatments would affect the survival of soilborne Listeria innocua, a non-pathogenic surrogate for the human pathogen L. monocytogenes, either applied near the time of cover crop planting or near cover crop termination. We hypothesized that cover crop based ST would increase soil moisture, reduce weed biomass, reduce nitrate-nitrogen leaching, increase soil microbial biomass carbon, increase microbial functional diversity, and fruit quality, without sacrificing yield or net profitability. We also tested the hypothesis that cover crop mulch would prevent the contamination of muskmelon fruits by soilborne L. innocua.</p> <p>In one year, the earlier termination of cover crops in conventional tillage plots and also the use of a rye-vetch biculture lowered the C:N ratio of cover crop biomass. Cover crops and strip-tillage did reduce weed biomass, though not consistently over both years. In-row soil moisture was higher in strip-tillage, and in-row soil temperature was higher in conventional tillage. Strip-tillage occasionally reduced the concentration of NO3-à  à ¬-N in leachate, this effect was inconsistent and only observed at a few sampling dates for only one year of the study. Rye-CT increased microbial biomass carbon over no cover-CT. During one year of the study, microbial functional diversity increased in rye and rye-vetch plots. The proportion of fruits that were marketable was increased under strip-tillage, as were several measures of fruit quality, but only in 2016. Populations of L. innocua introduced to the field in Oct. were able to overwinter and were detected the following May. The survival of May-applied L. innocua was measured in the first year of the study and showed that populations were reduced under both rye and rye-vetch cover crops. Treatments had no effect on the contamination of fruits at harvest. An economic analysis had mixed results, no cover strip-till plots had the lowest profit in both years, and rye strip-tillage and rye-vetch strip-tillage out performed their respective conventional tillage treatments in one year.</p>