Progress report for GNE19-205
The main objective of this project is to enhance sustainable agriculture pursuits in New England by ensuring that management practices will not harm biological communities and the ecosystem services they provide. The specific research objectives of this project are to 1. Measure the effects of silage tarps on soil arthropod diversity and soil properties; 2. Measure the effects of silage tarps on crop outcomes of relevance and interest to the farmers; and 3. Determine the relationships between soil arthropod diversity, soil properties, and crop properties.
The purpose of this project is to determine the ecological and agronomic impacts of silage tarping. Silage tarps are impermeable plastic films that are placed over crop beds with the primary purpose of reducing weed prevalence. They are widely used in the Northeast United States and can reduce tilling needs. However, while silage tarps have had promising initial results, there is very little research regarding their impact on soil ecology.
In particular, the impacts of silage tarps on soil arthropods (organisms such as beetles, mites, springtails, ants, and millipedes) is largely unknown. This is concerning because soil arthropods make up an important part of the soil community and play important roles in ecosystem functioning. Through actions such as carbon mineralization and fragmentation, aggregation, litter translocation, soil structure creation, and interactions with microbes, soil arthropods can contribute to agricultural sustainability and soil restoration.
Given the contributions of soil arthropods to soil health, it is important to be wary of the impacts of silage tarps on their populations. It is unideal if silage tarping inadvertently causes soil degradation through thwarting soil arthropod communities. Monitoring the effects of silage tarps on soil arthropod diversity in a variety of soil types and over time are important steps in ensuring that this management decision can provide long-term benefits to farmers. This research will help guide farmers to making decisions that harmonize farm sustainability and environmental stewardship.
Location and design:
Field work for this project will take place in the summer of 2021. This research will take place on three farms in northwestern and north-central Vermont (specific farms to be confirmed). We will use three treatments: 1. silage tarps, 2. no tarp and tilled, and 3. no tarp and not tilled. The treatments will be laid out in a randomized design, in 6m x 12m blocks. Every farm will have five complete set of treatments that will be situated in an area of a homogenous soil type. The tarps at all three farms will be applied within the same week in mid-May. In early June, after three weeks of tarp duration, we will remove tarps and plant the same variety of leafy greens (transplanting seedlings reared in a greenhouse) in all treatments and farms (tarps are often used for leafy greens). In the treatment without tarps but with tillage, we will use a hand hoe to manually till the plots before planting seedlings. Planting and rearing techniques will be uniform across farms. Farms will have the same fertilization regime and will not use pesticides or herbicides. Farmers will be allowed to keep and sell the plants.
We will collect soil arthropods at three weeks of tarp duration (but before tarps are removed), and then again two and six weeks after de-tarping. At each sampling period, we will take three randomly positioned samples per treatment plot and will collect soil arthropods using two methods: pitfall traps and the Berlese funnel method.
Pitfall traps are collection cups placed in the soil with their openings level to the surface. Organisms moving across the soil surface randomly fall and are trapped in the cups. In the Berlese funnel method, a soil sample is placed in a funnel and exposed to a bright light from above. Organisms move downward to escape the light’s heat and dryness, and are funneled into a collection cup. Pitfall traps generally capture surface crawling organisms while the Berlese funnel method captures arthropods that live in the soil. Using these two methods helps collect a wider array of soil arthropods and more broadly understand the soil community. These methods are chosen in part because they cause minimal damage to fields.
After collection, the specimens will be taxonomically classified (at least to order, with some orders to family level). From this we will calculate diversity metrics including species richness and Shannon’s diversity.
We will measure soil temperature and soil moisture weekly during tarp coverage. Each sampling period we will take measurements at four times during the day, at 8am, 11am, 2pm, and 5pm, and at random locations in each treatment plot. This will give us an understanding of the daily fluctuation of soil conditions. Soil moisture and soil temperature will be measured using soil probes. We have chosen these variables because they are the main immediate effects of tarps on soils and are likely correlates with arthropod diversity and crop outcomes.
In each treatment, we will measure weed prevalence (percent coverage in a randomly chosen 0.25 x 0.25 m2 area) weekly from tarp application to crop harvest. We will also measure crop height and width (mm) and pest damage (percent of outer leaves damaged by pests) on a randomly chosen plant in each treatment plot. We will take these measurements weekly from crop planting to harvest. This allows us to understand impacts of tarping on various crop outcomes and explore relationships between soil arthropods, soil properties, and crop characteristics.
Project delay due to COVID-19:
We initially planned for this project to take place in the summer of 2020. Due to COVID-19 restrictions and uncertainty, we postponed all activities to the summer of 2021. All project activities mentioned above (and in the original application plan) will take in 2021.
In the spring of 2021, we will begin purchasing research materials and making plans with partner farmers. We have already identified a field assistant to help with this work. In the late spring and in the summer of 2021, we will carry out fieldwork. During this time, we will also begin processing samples in the lab, which will continue into the fall of 2021. In the winter of 2022, we will present at the VT Veg and Berry Growers Association, and in the spring of 2022 we will present at an academic conference (such as the International Association of Landscape Ecology-North America). Between the winter and summer of 2022, we will also prepare our written deliverables, including "biodiversity reports" for each farm, a white paper for publication with UVM extension, a blog post or website article, and an academic paper.
Education & Outreach Activities and Participation Summary
Because this project has not yet begun, I have had limited opportunities to share this research. I have given two presentations, one of which was to an academic audience, and the other was to a variety of people including farmers and agricultural educators. This second conference was the CART -- Sustainable Food Systems Transitions conference at UVM in July 2019. As the project begins, I am excited to more actively engage with farmers and other people.
Because of receiving this SARE grant, I have been connected to other researchers in the New England area who also work with tarping systems. In particular, I am working with Sonja Birthisel, Suzanne Ishaq, and Alicyn Smart at the University of Maine and Natalie Lounsbury at the University of New Hamsphire. We successfully submitted a proposal to the Northeast IPM center to fund a working group focused on tarping systems (award received February 2020). This working group has met twice and brings together around 20 researchers, farmers, and extension personnel to enhance knowledge, communications, and research on tarping systems in the Northeast. As part of this working group, we are compiling a report of tarping knowledge for wide dissemination.
Through research and initial communication with farmers, researchers, and extension personnel, I have learned an incredible amount about sustainable agriculture systems in the Northeast. Most notably, I've found gained a huge appreciation for the farmers and extension personnel who mix innovation, skill, and their own research to ensure food production for their community. They do this in the midst of changing climates and increasingly aggressive pests and diseases. As I continue my research on this project, I am excited to continue to learn from these people.
I plan to continue to work on questions of sustainable agriculture, entomology, and land management throughout my career.