Emily Locke

The use of high tunnels-- structures made of polyethylene film covering agricultural fields-- has been increasing in the United States as demand increases for local and organical produce. Thus, it is important to assess long-term effects of high tunnels on soil health. High tunnels will likely affect soil microbial activity as they strongly affect soil moisture and temperature. Microbial activity is essential to nutrient cycling and overall soil health, which in turn supports crop yields. One measure of microbial activity is extracellular enzyme activity, since the enzymes present in the soil show how many microbes are active and what they are doing. My project compares potential microbial extra-cellular enzyme activity inside and outside of high tunnels in a vetch cover crop-tomato rotation at four points in the growing season. The experiment is replicated in Minnesota and Kentucky, which have different soil types and climates. I measured the potential activity of four hydrolytic enzymes (B-glucosidase, phosphatase, N-acetylglucosaminidase, cellobiohydrolase) and two oxidative enzymes (peroxidase and phenol oxidase) using colorimetric and flurometric methods. I expect that microbial activity will increase as temperature and moisture increase up to a point. Thus, I hypothesize that microbial activity will be greater in high tunnels than in open fields, since water inputs can be controlled so soil will be more consistently moist and because soils in high tunnels are warmer than in open fields. I also hypothesize that microbial activity will be greater in Kentucky than in Minnesota due to warmer temperatures.