Mixed-species cover crop plantings (aka Cover Crop Cocktails) offer multiple benefits to producers. Through a collaboration with five Oahu-based producers, this project aims to identify viable cover crop cocktails for producers in Hawaii. Research and field demonstrations will be used to evaluate economic costs, and to measure effects of cover crop plantings on soil health. Information will be shared with producers through on-farm field days, presentation at the Hawaii Ag Conference, and through Oahu RC&D’s Cover Crop Handbook.
Project Objectives and Target Dates:
- Identify cover crop species currently used and available in Hawaii.
- Conduct a survey of cover crop users, seed sales locations, and agricultural professionals to identify which cover crop species are currently in use / October 2016.
- Summarize information related to planting rates, costs, days to maturity, etc. / November 2016.
- Utilize information to determine cover crop cocktail mixes and planting rates / December 2016.
- Evaluate economic costs and soil health benefits of mixed-species cover crop plantings.
- Summarize economic costs (ie. cost of seed per acre) of cover crop cocktails / January 2017.
- Establish five demonstration plots in diverse geographic locations on Oahu / May – September 2017.
- Conduct physical, chemical, biological, and agronomic evaluations at pre-project and post-project intervals / approximate dates: March 2017, September 2018:
- Physical: moisture, temperature, bulk density.
- Chemical: pH, total nitrogen, total carbon, phosphorus, potassium.
- Biological: presence of earthworms, soil respiration (Solvita).
- Conduct agronomic evaluations of two seasons of cover crop cocktail plantings on cooperating farms:
- Agronomic: biomass of cover crop and, where feasible, weeds (used to determine relative weed suppression), percent soil coverage, presence of beneficial insects, estimated plant available nitrogen (tissue culture and cover crop calculator tool from the University of Hawaii CTAHR).
- Identify obstacles (“pain points”) and potential solutions for small farms adopting cover crop cocktails in Hawaii.
- Gather anecdotal feedback and observations from host farms following each / March 2018, December 2018, and throughout project period.
- Facilitate collaborative learning process through data collection, experimentation and feedback from technical advisors. / throughout project period
- Summarize lessons learned to inform decision-making about cover crop cocktail use at the farm-level and simplify the onboarding process for farms adopting cover crops. / December 2018
- Document field practices and equipment used by cooperating farms along with pros and cons. / December 2018
- Share results with producers and other agricultural professionals.
- Employ surveys to gauge familiarity with common cover crop species / October 2016, July 2018, March 2019.
- Hold two field days to demonstrate cover crop cocktails. Field days will be held at host sites, and will include presentations from the host farmer(s), 2-4 agricultural professionals on featured topic(s), and a tour or hands-on activity / September 2017, September 2018.
- Incorporate findings into a revised edition of the Cover Crop Handbook produced by Oahu RC&D / March – June 2019.
- Present findings at the 2017 Hawaii Agriculture Conference (or similar venue) / August 2017.
- Disseminate resources, results and related information via social media networks and producer-to-producer networks / entire project period.
Project methods are outlined in the objectives and target dates.
Our call for collaborators for the cover crop cocktail trial received strong interest from small-scale vegetable producers using organic practices. Having worked closely with large-scale operations to develop and promote cover crop practices appropriate for Hawaii’s farms and soils in the past, we seized on this as an opportunity to extend the use of cover crop technologies to a broader audience in our state. As we implemented our first round of on-farm field trials in 2017, our choice to collaborate with small farms coupled with our participatory research process has uncovered a number of unforeseen challenges as well as a number of insights to tailor our methods to better serve Hawaii’s small farm sector:
- None of the cooperating farms in the trial possess grain drills, no-till drills, roller-crimpers, flail mowers, or other equipment commonly used to manage cover crops and frequently cited in cover crop extension literature. Two of the farms do not possess or have reliable access to tractors. Additionally, the focus of our cooperating farmers on vegetables and tree crops (bananas, breadfruit, tropical fruit) results in a shortage of experience regarding the field practices used to plant and terminate cover crops. We adjusted to these challenges by broadening our research process to document farmer feedback on the obstacles or “pain points” they encountered during the 2017 cover crop trial, the results of which we plan to incorporate into our 2018 field day topics and subsequent cover crop manual update. We also reduced the size of the trial plots not only to accommodate the size and cropping system of each farm, but also to reduce the potential for costly negative impacts on subsequent cash crops given the amount of problem solving (and likelihood of mistakes) required to overcome relative inexperience and equipment limitations.
- Our cooperating farmers work in drastically different soils (e.g. vertisol, oxisol, mollisol), and growing conditions, including variations in annual rainfall between 700 and 1,100 mm. and annual solar radiation between 160 and 210 W / sq. m. This complicates our goal of of identifying uniform, effective cover crop cocktails and seeding rates to promote, but forces us to recognize the challenges confronting farmers interested in adopting cover crops in Hawaii. We’ve adapted to this by taking a two-prong approach:
- We’re trialing a uniform cover crop cocktail recipe across all farms during two seasons (2017-2018) in an attempt to identify a “one size fits all” recommendation, which we anticipate being of use to the most farms possible, especially first time cover croppers.
- During the trial’s second season, each farm will develop a custom cover crop cocktail tailored to their specific cropping system and growing conditions. We anticipate these blends being useful to neighboring farms and farms with similar growing conditions and/or cropping systems on all islands in the state. We trust that this farm-level participation in the trial design will tap into more creativity and deep site knowledge.
- We continue to explore opportunities to complement the on-farm trial plantings with a larger, lower-cost planting of multiple cocktails at a single site. Plans to conduct this planting with Pioneer in 2017 were postponed and ultimately canceled.
- We adjusted the methodology to better integrate farmer participation, innovation and learning, as outlined in objective three.
- We integrated a new tool released in 2017 by Dr. Wang of UH CTAHR, in conjuction with Oregon State University faculty, which provides a protocol and spreadsheet to estimate the plan available nitrogen provided by a cover crop in several of Hawaii’s most common agricultural soil classes. We are “road-testing” this tool to assess its value for small farmers and provide better information for farm-level decision-making regarding cover crops adoption and use.
The first of two seasons of cover crop plantings was completed on six cooperating farms during the summer of 2017. Data has been collected for the first season as outlined in the project objectives and target dates. Raw results are attached, when available, and will be included in the final project report otherwise (CCC-Results). The plantings were largely a success and provided a lot of feedback that will be incorporated to improve the 2018 season of on-farm plantings. One of the cooperating farms had a failed planting due to a family emergency (death in the immediate family), though an additional cooperating farm was included as a volunteer (Jay Bost, Senior Farm Coach with the GoFarm Hawaii incubator program).
Several lessons learned during 2017 that will be used to improve for the 2018 season:
- There was a problem with shipping the fresh sample tissue culture for analysis to the out-of-state lab used for soil testing. Several different drying facilities were used as a result, which may have skewed the results of the analysis. Preparations are being made to use a single facility for analysis of the 2018 plantings.
- Integrating farmers into the field work to collect data on the cover crop was a invaluable opportunity to spend quality time assessing the cover crop and gathering feedback. However, field work needs to be completed in 1-2 hours in order to fit into their schedules. We’ll work to secure additional staff members to make this possible in the 2018 plantings. The shortage of help in the field limited data collection on weed abundance and soil moisture.
Educational & Outreach Activities
We organized a well-attended cover crop cocktail field day at Kahumana Farm in conjuction with their annual Farm Fair. Through partnerships, the field day featured an all-star panel of soil health experts and farmers: Dr. Jen Kucera (NRCS), Gabe Brown (Brown’s Ranch), Bob Shaffer (Soil Culture Co.) and Jayme Barton (HARC and project technical advisor). In addition to small group time with all of the panel experts, participants had the opportunity to evaluate a six species cover crop cocktail alongside single species plots of each of the species in the cocktail (sunn hemp, lab lab, oilseed radish, black oats, buckwheat, sorghum-sudan grass).
In 2017, the project coordinator gave three presentations on cover crop cocktails to groups of farmers at the following events: Hawaii Farmers’ Union United Annual State Convention, No-Till, Small-Scale Farming Workshop (one event on the island of Oahu and a duplicate event on Hawaii Island) (See attached: HFUU-2017-Convention;Cover-crop-cocktails-No-Till-workshop-HARC)
Our project coordinator and technical adviser provided cover crop consultations and site visits to all cooperating farmers at the beginning and end of the 2017 trial, as well as an additional farmer.
We conducted an on-farm demo as part of the “Local Seeds for Local Needs” event hosted by CTAHR and GoFarm Hawaii at the Waimanalo Agricultural Research Station on September, 23, 2017. We shared information on cover crop cocktails and the trial activities, including a demo plot of sunn hemp, buckwheat and black oats.
A poster was accepted for presentation at the 2017 Hawaii Agriculture Conference, highlighting the cost and benefits of cover crop cocktails, as well as the ongoing trial. (See attached: CCC-AgConferenceFinal-LEFT CCC-AgConferenceFinal-RIGHT)
Participants in our 2017 cover crop field day indicated an increased knowledge of cover crop use in Hawaii (N=29, average response 9.2 on a 10-point scale).
Participants in our 2017 cover crop field day indicated a high likelihood of applying the information learned on their property (N=28, average response 8.9 on a 10-point scale).
Six cooperating farmers trialed cover crop cocktails alongside single species cover crop plantings and assessed costs and benefits, and identified "pain points" or obstacles to adopting cover crop cocktails.
In 2017, our primary outcomes were the first season of cover crop cocktail plantings at cooperating farms (See Methods and Results) and an active schedule of outreach events to share information on cover crop cocktails and the ongoing trial (See Education and Outreach). These two accomplishments lay the groundwork for success in 2018, when we will draw on the lessons learned in the on-farm trials to promote and host an expanded Cover Crop Cocktail Field Day. To avoid the potential for an infinite and unmanageable number of recipes, we decided to focus our efforts on one standard mix and five custom mixes developed with each cooperating farm in the trial. This approach aligns with input from producers who need practical and economically viable options.
In 2016, the greatest outcome was an increased understanding of the various cover crop species available in Hawaii. We’ve spent a lot of time musing about recipes, and feel like there is not a lot of published data that offers definitive seeding rates for mixed cover crop plantings.
In 2016, two student interns spent the summer conducting research and identified a suite of species commonly used for cover crops, and then interviewed producers and agricultural professionals to narrow our focus to species common and readily available in Hawaii. This effort resulted in a spreadsheet and a working list of 11 species. Cover Crop Inventory_11.29.16
For the majority of the 11 species we were able to identify planting rates, growth habits, and seed cost. And for about one-third of these species we found published seeding rates when used in a mixed planting. This information was used to identify four potential “recipes” for cover crop cocktails and to estimate relative costs.
Additionally, we developed and distributed a cover crop survey. Forty-six people responded.