What multi-regional experiments look like:

A snapshot in time across the U.S.

Multi-Regional research projects ask the same questions and run similar experiments in different parts of the country simultaneously so that results are relevant to a broader range of farmers. One challenge that goes unseen to most people outside of this kind of research is the coordination of experiments when climate varies so greatly between regions. In our case, this affects the timing of planting cover crops and experimental crops, when we can add livestock to graze, the types of livestock that are regionally relevant (e.g. goats vs. sheep), and the experimental crops that can be grown. Here is a photo depiction of what this looks like in the field across our three experimental regions in California, Minnesota, and Maryland, where the summer and winter seasons are very different. All pictures were taken at the end of April, 2021. 

While all states will follow the same protocol, regional differences in climate cause each state to follow different timelines. For instance, California is one step ahead of Minnesota and two steps ahead of Maryland. This image shows a snapshot taken at the same time for each experimental farm, but in different stages of the project for each region. California has already planted its cash crop spinach following grazing, while Minnesota is currently grazing its cover crop before planting spinach, and Maryland is planting their cover crop plots for grazing.  Note the size difference in the plots between California and Maryland as well. This is due to the difference in commercial growing of the spinach crop, where California tends to grow larger fields than the other experimental regions.

The three states that are collaborating on this CDFA Specialty Crop Multistate Program grant are all at different stages of the cover crop/crop cycle due to climate differences and a crop (spinach) that is a cool season plant. In Minnesota, the cover crop mix (cereal rye, clover and radish) was grazed once in the fall, then buried under snow for much of the winter. It was grazed again in April, once the snow melted. Spinach will be planted in June. In contrast, in California, the cover crop was only grazed once in March, and then was planted into spinach because spring is typically shorter and there is a smaller window for successfully growing spinach. Spinach will be done growing by June in California. In Maryland, the cover crop was first planted in March and will be grazed around June, with a fall planting of spinach, rather than a spring planting like the other states. These differences in the cover crop/crop cycle will add to the robustness of our analysis of the impacts of grazing on foodborne pathogen risk and soil health indicators.

Regardless of the timing, all states will be following the same protocols for monitoring foodborne pathogens and soil health indicators. We will sample the baseline soil before the grazing and the soils 7, 30, 60, 90 and 120, 150 days after the last grazing event. We will also collect fecal samples of grazing animals before and after the grazing event. The samples will be analyzed and compared for the presence of pathogens (E. coli O157, non-O157 Shiga toxin producing E. coli, and Listeria monocytogenes) & the survival duration of generic E. coli among the three treatments (fallow, ungrazed cover crop and grazed cover crop) throughout the whole period. When spinach is done growing, potential transfer to spinach will be determined by testing spinach leaves at harvest. 

For soil fertility, soil samples will be taken at the time of spinach planting and analyzed for soil pH, organic matter content and macro and micro nutrients. Soil samples will be collected during spinach growth to be analyzed for soil fertility again, as well as soil health indicators such as aggregate stability, active carbon and potential nitrogen supply. With this first year of data on both foodborne pathogens and soil fertility and soil health, we will work towards better understanding the potential benefits and tradeoffs of implementing sheep grazing in annual vegetable production in three different climates across the U.S.

Funding for the project was made possible by the U.S. Department of Agriculture’s (USDA) Agricultural Marketing Service through grant #  AM 19-1046-001-SF. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the USDA.



AgNet West Media Coverage 

Our project was featured on AgNet West, the largest farm radio network service in California.

Here is an exceprt from the article:

Researchers are looking into the benefits that livestock grazing presents for organic farming systems.  The project is being made possible by a nearly $1 million U.S. Department of Agriculture (USDA) Specialty Crop Multistate Program grant.  The impact of sheep grazing on cover crops will be studied to determine the effect it may have on soil health and bacterial population dynamics.

To read the full article click here!


Sheep graze on winter cover crop at Russell RanchUCANR Blog Post

The University of California Division of Agriculture and Natural Resources (UCANR) released a blog post about our project! You can read about it here: https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=42528


Specialty grant to examine impact of integrating animals in crop rotations

Multi-state research will explore benefits and potential risks

The Organic Center is pleased to be a part of a collaboration among university, government, and non-profit partners that will receive a major USDA Specialty Crop Multi-State Program grant to look at the benefits of livestock integration through cover-crop grazing on bacterial population dynamics, soil building, and environmental health.

The nearly $1 million project titled “Evaluating the food safety impacts of cover-crop grazing in fresh produce systems to improve cover crop adoption, crop-livestock integration, and soil health” is led by the University of California, Davis in partnership with The Organic Center, USDA’s Agricultural Research Service, the University of Maryland Eastern Shore, and the University of Minnesota.

“Fresh produce growers and their advisors will benefit from learning about the impacts of integrating livestock grazing with winter cover crop management on soil health including soil organic matter, nutrient cycling and reduced nitrate leaching, and potential food safety risks discovered in this project to make decisions on adoption, management, and environmental benefits of WCC in annual vegetable systems,” said Alda Pires, University of California Cooperative Extension specialist and lead principle investigator in the study.

Livestock grazing of cover crops could be beneficial for organic systems, because it maximizes the strengths of cover cropping, including enhanced soil fertility, structure, water infiltration and storage, and reduced nitrate leaching, while addressing challenges that have limited the expansion of cover crop use. These challenges include concerns over cover crop water use and nutrient immobilization, which could increase deficiencies and increase input costs of the crops that follow.

Many growers consider livestock grazing of cover-cropped fields in fresh produce operations as a way to enhance soil health and environmental benefits by increasing carbon inputs and nutrient cycling.

“This study will allow farmers to complement the benefits of both cover cropping and livestock integration into cropping systems,” said Jessica Shade, the Director of Science Programs from The Organic Center. “Like cover cropping, integrating animals into cropping systems can be beneficial to farm environmental impacts and profitability by improving nutrient cycling, reducing dependence on external inputs, improving soil health, and diversifying profit streams.”

Unfortunately, despite the well-known benefits of animal-crop integration, concerns over microbial food safety are limiting the expansion of animal integration into cropping systems. Recent research has shown that integrated crop-animal systems perform well in keeping pathogens out of meat, but additional research is needed to examine the synergistic impacts of the use of livestock for cover crop grazing on ecosystem health and food safety.

This project will fill this research need by examining food pathogen persistence and survival in soil and transfer to vegetable crops, and the relationship between soil health properties, environmental factors and pathogen survival in grazed cover crop-vegetable production in three states.

Researchers will measure changes in soil health indicators over two years of grazed cover crop-vegetable production, and assess benefits and potential tradeoffs of vegetable cash crop productivity.

The research team is multi-institutional, multi-regional, and interdisciplinary, and includes:

The Organic Center will help lead outreach efforts focusing on the benefits of grazing and food safety impacts such as online tools, outreach events, conference presentations, and publications targeted to growers, policymakers and consumers.