Cover Crops Under Cover: Evaluating Costs, Benefits, and Ecosystem Services of Cover Crops in Year-Round High Tunnel Production Systems

Project Overview

LS16-272
Project Type: Research and Education
Funds awarded in 2016: $241,615.00
Projected End Date: 09/30/2019
Grant Recipient: University of Kentucky
Region: Southern
State: Kentucky
Principal Investigator:
Krista Jacobsen
University of Kentucky

Commodities

  • Vegetables: greens (lettuces), tomatoes

Practices

  • Crop Production: continuous cropping, cover crops, nutrient cycling, organic fertilizers
  • Education and Training: on-farm/ranch research, participatory research
  • Farm Business Management: budgets/cost and returns, marketing management, agricultural finance
  • Natural Resources/Environment: carbon sequestration
  • Pest Management: mulches - killed, weed ecology
  • Soil Management: green manures, soil analysis, nutrient mineralization, organic matter, soil quality/health

    Abstract:

    The use of cover crops is an integral part of sustainable field cropping systems, with well-documented benefits to soil health, pathogen suppression, and sustaining crop yields. However, cover crops have been utilized to a lesser extent in year-round, intensive high tunnel cropping systems. This is due to both biophysical constraints in these systems, such as short windows for non-cash crops, as well as economic constraints, such as potential lost revenues from cash crops sacrificed by growing cover (non-cash) crops. This situation presents a set of trade-offs common to sustainable agriculture systems – balancing production with other ecosystem services enhanced by conservation practices that take lands temporarily out of cash crop production. High tunnel systems offer a compelling example of such trade-offs. These unheated greenhouses are passively heated and ventilated by physical manipulation of the plastic covering the structure. These highly productive, predominantly soil-based systems have been growing in popularity due to cost share programs and the growth of year-round market opportunities. In the Southeast, tunnels afford producers the ability to extend warm-season crops approximately one month earlier and later, and allow production of cool-season crops throughout the winter months. Although this may increase the availability of locally produced foods, the intensity of these production systems leave little time for integrating cover crops and/or fallow periods typically associated with sustainable agriculture practices. We approached this project from an interdisciplinary, systems-oriented perspective via three main objectives. Objective 1 was a survey of high tunnel growers in the southern region to identify current practices and potential temporal windows in which cover crops may be integrated. Objective 2 was focused on the trade-offs discussed above through evaluating the economic costs and ecosystem service benefits of cover crops in tomato high tunnel rotations. This multi-state field experiment integrated cover crop treatments into a spring-planted tomato production system on research farms in Kentucky and Tennessee. Ecosystem services evaluated include soil parameters associated with soil health, nitrogen leaching, weed seed bank management, and yields.  Objective 3 was focused on identifying novel cover crops for high tunnels. Specifically, we evaluated a suite of warm- and cool-season cover crops for rapid biomass production, weed suppression, and other desirable traits identified by our participating farmers.  Multi-state, on-farm trials were conducted with high tunnel growers in Georgia, Kentucky, and Tennessee.  Project results have been communicated through numerous state and regional grower conferences, on-farm trials and many outreach activities.  Additional outreach products (fact sheets, etc.) are in development and will be made available through the he multi-state Center for Crop Diversification (http://www.uky.edu/Ag/CCD/) and UT Organic and Sustainable Crop Production Program (http://organics.tennessee.edu).  Results have been communicated to academic audiences through presentations at conferences, with two peer-reviewed articles in preparation.   

    Project objectives:

    Objective 1: Conduct a high tunnel grower survey to characterize high tunnel cropping systems and existing cover crop use in high tunnels in the Southern SARE Region through a high tunnel grower survey.  This survey was designed to gather management practice data for high tunnels to be used to characterize management techniques regionally, establish baseline practices, and include market information that is in high demand in local and regional food systems including early and late season pricing for tunnel-produced crops.  Survey responses were collected from 106 high tunnel producers through online (Survey Monkey) and print surveys from producers without internet access.  The survey was conducted during Fall/Winter 2018 – 2019. 

    Objective 2: Evaluate the ecosystem services and economic costs of using cover crops in high tunnel crop rotations. A two-year, two-site study was conducted on the University of Kentucky Horticulture Research Farm and the University of Tennessee East Tennessee Research and Education Center.  We incorporated winter cover crops into tomato production systems, and compared economic and ecological costs and benefits of cover crop treatments with a continuously cropped (year-round) tomato-lettuce rotation. The cover crop treatments included a cool season grass (winter wheat) alone, a cool season legume (crimson clover) alone, and a cool season grass-legume mixture (winter wheat and crimson clover) together. The ecosystem services evaluated included parameters associated with soil health, nitrogen leaching losses, weed seed bank dynamics, and yields. Economic parameters evaluated will include costs such as inputs (fertility, irrigation, water, seed, etc.), opportunity costs lost from not growing a cash crop, fertility (nitrogen) credits from the cover crop, labor requirements, and gross returns from yields.

    Objective 3: Identifying novel cover crops that fit the unique “niche” of high tunnel production systems.  This objective consisted of a two components, one research-focused and the other outreach-focused.  The research component consisted of a two-year study to evaluate novel cover crop candidates at the UK Horticulture Research Farm conducted from Fall 2016 – Spring 2019, and b) On-farm trials with four participating farmers in Georgia, Kentucky, and Tennessee.  Cover crops were selected for the novel cover crop trials to represent both traditional cover crops grown in the open field in the region, as well as some more unique accessions used in forages or being developed as novel new crops for the region.  The novel trails consisted of evaluations of cool season and warm season cover crops, each evaluated for two years.  The outreach component consisted of the University personnel working with the participating growers to identify key high tunnel management challenges they the farmers wanted to utilize cover crops to manage, including knot nematode suppression, compaction mitigation, and enhancing soil organic matter and overall soil health.  Participating farmers in each state then trialed the selected cover crops on their farms. 

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.