Covering New Ground: Tropical Cover Crops for Improving Soil Quality

Final Report for EW98-012

Project Type: Professional Development Program
Funds awarded in 1998: $84,500.00
Projected End Date: 12/31/2002
Matching Non-Federal Funds: $54,000.00
Region: Western
State: Hawaii
Principal Investigator:
Richard Bowen
Department of Nat Res and Envir Mngt
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Project Information


This project was established to collect, improve access to, and distribute information about cover crops and green manures appropriate for the Pacific Region. The project has successfully developed a list of 26 plant species (with 17 more possible candidates) and provided plant descriptions available at a web site. Information from the web site can be printed out and a search engine can be used to gather specific information. In conjunction with the development of this body of web-based information, a series of 11 demonstration sites were established on 6 islands. They demonstrated the use of cover crops or green manures under different crop production systems that represent local farmer needs. A training workshop was held with participation from representatives from CES, NRCS, local farmers, private agricultural consultants, professionals from Community Colleges, and agricultural professionals from Guam, Palau, and Kosrae. The workshop included segments about the use of cover crops/green manures, a cover crop/green manure recommendation exercise, a computer exercise to use the web site database, classroom and field exercises in soil quality, and a visit to a cover crop/green manure demonstration site. During the final phase of the project, workshops and/or field days were held at each demonstration site. The website was further refined. The cover crop/green manure information from the database was incorporated onto a CD-ROM and into a series of leaflets about the tropical cover crops and green manures.

Project Objectives:

1. Determine a set of 20 tropical cover/green manure crops suitable for Hawai`i and the Pacific Region and promote their use.

2. Improve access to information on tropical cover/green manure crops so that agricultural professionals can make better recommendations and producers can make better management decisions. Make cover/green manure crop information accessible in print, CD-ROM, and a web-based database.

3. Establish 10 cover crop demonstration sites representing different tropical crops and cropping systems to gain experience and prepare for field days for the public.

4. Carry out CES & NRCS training about selection and economic impacts of cover/green manure crops. Link training in the use of cover crops to soil quality measurements in cover cropped areas. Include crop recommendation exercises.

5. CES & NRCS Agents apply their knowledge by conducting cover crop training for the public via field days at demonstration sites.


Prior Situation

The information gleaned from cover crops research in Hawai`i and the Pacific had never been brought together in a readily accessible form. Over the years, work on cover crops was scattered amongst many islands, different agencies or individuals, and separate projects. In addition, there was no economic analysis of this work, making it sometimes difficult to justify the use of cover crops to farmers. Extension of the results of these previous projects and the addition of economic analyses would extend results to a wider audience and encourage more use of cover crops in the Pacific Islands.

Prior Work

The NRCS Plant Materials Centers on Moloka`i and Guam have been leaders in the research and introduction of cover crops to the islands. Sunnhemp and tropic lalo are two of the most commonly used covers that they have promoted. At the College of Tropical Agriculture and Human Resources a number of projects have been conducted over the past ten years.

Carl Evensen (Dept. of Agronomy and Soil Science) did dissertation work on crotolaria, calopo, and centrosema. From 1990 - 1992 he looked at over 50 small grain cover crops for erosion and weed control in sugar cane followed by a large scale demonstration of 2 species (oats and rye grain) on 20 acres. With the decline of sugar cane his work has now turned to focus on orchard cover crops including 6 perennial grasses and one legume and 4 small grain covers in lychee and coffee. Samir El-Swaify and Russel Yost have also conducted research on the effect of cover cropping on soil erosion both in Hawai`i and internationally. Scott Campbell has worked extensively with CES in Hawai`i and the Pacific on database and computer based information projects.

Hector Valenzuela and Joe DeFrank (Dept.of Horticulture) have worked with cover crops in no-till systems in vegetable crops as a method of weed control and to build up beneficials or as trap crops for insect control. Alton Arakaki and Brent Sipes evaluated cover crops for resistance to root-knot nematode as a rotation for taro and okra. Extension agents John Powley and others have looked at a wide range of grasses for their resistance to sugar cane aphid, a major pest recently introduced to Hawai`i. Valenzuela has worked in cooperation with the World Sustaibale Agriculture Association (WSAA) on a long term comparison of compost, green manures, and chemical fertilizers at the Waimanalo Experiment Station. Since 1993, 30 cover crops have been evaluated in their project. A field day was held during a WSAA sustainable agriculture conference and handouts were prepared. Research reports and handouts, however, have not been available to the general public. DeFrank has done both on-farm and on-station work on cover crops in fruit orchards and tested Japanese eggplant varieties in a living mulch trial using Rhodes grass (Chloris guyana).

The Agricultural Development in the American Pacific (ADAP) Project
carried out a year of on-farm cover crops work in American Samoa, Hawaii, Pohnpei, Guam and Saipan. Results were published in the Pacific Islands Farm Manual in 1994 which has had limited distribution (50 copies were produced). Ray McDuff on Saipan has continued worked with crotolaria in vegetable cropping systems. Frank Cruz has been working towards creating demonstration plots in orchards.

Many of the international agricultural research institutes (IITA, CIAT, IRRI, ICRISAT, and ICRAF) have done work on cover crops but this work has had little exposure in the Pacific Islands and extension agents and NRCS personnnel have generally not received this information.

Laurie Drinkwater (Rodale Institute) and Fred Magdoff (Universty of Vermont) who worked on the first year of the Northeast SARE Soil Health Training indicated that hands-on activities were the most important aspect of their soil quality training sessions. They also utilized existing demonstration sites to illustrate the striking differences in soil quality measurements using simple methods to determine infiltration and other parameters.


Click linked name(s) to expand/collapse or show everyone's info
  • Alton Arakaki
  • Dr. Scott Campbell
  • Frank Cruz
  • Dr. Joe DeFrank
  • Richard Ebesu
  • Lisa Ferentinos
  • Robert Joy
  • Ray MacDuff
  • Larry Shinshiro
  • Jody Smith
  • Dr. Hector Valenzuela

Education & Outreach Initiatives



A half-time project coordinator was hired to oversee all aspects of the project and to assist major participants in forming a cover crops working group. Participation from individual farmers and organizations (e.g. the Hawai`i Farm Bureau, the Hawai`i Organic Farmers Association) and commodity groups (e.g. the Tropical Fruit Growers Association, Hawaii Forest Industry Association, and others) as well as university and agency representatives was encouraged. Farmers that had been involved in previous cover crops work were requested to serve as members of the working group. The working group developed a priority list of twenty six crops, those most promising for annual cropping systems (vegetables and herbs) and perennial systems (fruit or nut orchards and agroforestry systems). The working group assisted the coordinator in collecting relevant material for the database on the identified crops. The working group met four times during the project as well as communicated via email to allow Pacific Islands institutions outside of Hawaii to be full participants in this part of the project.

The coordinator surveyed farmers who have worked with cover crops to bring their input to the working group and the database. Eleven on-station and on-farm demonstrations on seven islands included some of the 20 priority crops identified by the working group.

The existing SAREP Cover Crops Database served as a model and shell for the cover crop information collected. The SAREP fields were utilized (common and scientific name, management practices, cropping system, environmental conditions, etc.). The developing database was reviewed periodically by the working group. It is available through the College of Tropical Agriculture and Human Resources' web site as well as on CD ROM for Pacific Islands without reliable world wide web connections. Easily reproduced leaflets were prepared for each cover crop available as downloadable .pdf files for printing and distribution by CES and NRCS. Printed copies are also available for clientele that don't have access to computers.

A three day training was held in Year 2. Due to high interisland travel costs, only one to two representatives from each island was able to attend the training. In addition to the representatives whose travel costs were covered by SARE funds, this event was open to those who can supply funds from their own agencies. NRCS provided funds for their personnel.

Follow-up, on-island field days were coordinated by those that attended the training with assistance from the project coordinator.

Project evaluation was done via a survey of CES, NRCS and other participants as well as by on-going monitoring of and feedback on the website.

Outreach and Publications

Dissemination of Findings

All information produced to date by this project is available at the Hawai`i Sustainable Agriculture Web Site:

This includes downloadable .PDF files on tropical cover crops and green manures.

The cover crops/green manures database information has been incorporated into the CD-ROM Portable Extension Office for Program Literature Exchange (PEOPLE) and can be ordered through I. Scott Campbell, UH Manoa TPSS, Sherman Lab, 1910 East-West Rd, Honolulu HI 96822, email: [email protected].

Outcomes and impacts:

Evaluations were sent out to CES agents, NRCS agents, farmers, and agricultural consultants who participated in the project. Based on their feedback, we have made the following observations:

Materials Developed by the Grant Project: In general the website, fact sheets and database were ranked as good with recommendations to include more color photos, more line drawings and more Hawaii specific information. Subsequently the web site and fact sheets have undergone significant revisions to address these issues.

Professional Development Impacts: CES/NRCS staff opinions were divided on whether their attitude toward and understanding of sustainable agriculture had changed. Most felt that they were better able to respond to farmer/rancher questions, and better able to assist in designing sustainable agriculture systems. However they still expressed a need for additional training in sustainable agriculture topics (“I need more time to try out new techniques”, “still could use more training.”)

Farmer Adoption: CES/NRCS agents reported that some farmers are trying cover crops and green manures as a result of the project. Sunnhemp is the green manure of choice because it produces a great deal of biomass and suppresses nematodes.
The following uses were reported:
• Ginger farmer using sunnhemp
• Taro farmer using sunnhemp
• New farmer using sudax/sunnhemp and buckwheat
• Vegetable Farmer using sunnhemp, buckwheat, susbania
• Orchard farmer using sudax/sunnhemp
Cover crops and green manures are still not widely used in Hawaii with two notable exceptions: the organic farming community and the Japanese Nature Farming community.

Training Methods: CES/NRCS staff were asked to rank the training methods used during the project. Demonstration sites, sustainable ag website, CD ROM, fact sheets, cover crop text book, soil quality text book, and the 3-day training were all well received. CES/NRCS staff were less positive about (and aware of) the sustainable ag lending library, availability of financial support to attend sustainable ag workshops, email communications on sustainable ag topics, and sustainable ag videos.

Topics for Future Training: CES/NRCS staff requested additional training in soil nematode and pathogen control, organic farming methods, biological control methods, pest and nutrient management in sustainable ag systems and utilizing animal waste systems in sustainable ag systems. Several individuals specifically requested additional field trips and workshops on sustainable agriculture themes.

Project Outcomes

Project outcomes:

COVER CROP/GREEN MANURE DATABASE: Our project identified twenty-six species of tropical cover/green manure crops suitable for Hawai`i and the Pacific. These species were evaluated and found to have applications in the tropical setting varying with rainfall and elevation. Selection criteria included successful field testing in Hawai`i or other Pacific regions, low indication of invasiveness for native species (non-twining, no prolific seeding, not dispersed extensively by birds, etc.) and gives preference for nematode resistance and seed/plant material sources readily available. Plant descriptions for tropical species are in-depth. Those for temperate species are in summary form with references (or hyperlinks) for further information.

The basic plant descriptions are available at the Hawai`i Sustainable Agriculture web site ( as well as downloadable .pdf leaflets for each plant. When using a standard search engine, the CTAHR home page can be located and the list accessed. The CTAHR site has its own search engine as well to locate the tropical cover crop and green manure information. We continue to improve the website to improve the search function, add photos, and make the site more user-friendly. The website has received 3345 hits from 3/6/00 - 12/17/02. In the time period from 12/31/01 - 12/17/02 we received 1598 hits with 85% coming from non-UH IP addresses.

The web site posting and regular updates are announced to Hawai`i agricultural commodity groups, agricultural educators, staff within CES and NRCS, and to members of the ADAP Project. The Agricultural Development in the American Pacific (ADAP) Project provides a network and clearinghouse for agricultural information for the pacific region. The following land grant institutions are active participants: American Samoa Community College, College of Micronesia, College of the Marshall Islands, Palau Community College, Northern Marianas College, University of Guam, and the University of Hawai'i at Manoa.

COVER CROP/GREEN MANURE DEMONSTRATION SITES: The demonstration sites are completed. Several extension agents joined the project after we began, so we redistributed funding to allow for more sites with smaller budgets. Since we have fewer limitations on growing seasons, we were able to be more flexible with timing for the demonstration sites.

Below is a summary of the status of the demonstration sites affiliated with the project (10 sites originally proposed).

1. Demonstration on managing weeds using cover crops in organically grown papaya ("mow and blow" mulching system) using two sorghum-sudangrass hybrids ('STE6' and 'Pacesetter') - Alton Arakaki, CES. Status: Completed. Location: Moloka`i Research and Demonstration Farm (Experiment Station, Moloka'i, HI)

2. Evaluating the effectiveness of cover crops (French marigold, sunn hemp, sorghum-sudangrass hybrids) to root knot nematode damage using bush beans as an indicator crop - Kali Arce, CES. Status: Completed. Location: Moloka`i Research and Demonstration Farm (Experiment Station, Moloka'i, HI)

3. Cover crop trials for weed control and nutrient inputs for organic papaya and vegetable production using sunn hemp, rapeseed 'Dwarf Essex', sesbania, sorghum-sudangrass hybrids 'Pacesetter' and 'Honey graze BMR', lablab, alfalfa 'WL711WF', New Zealand white clover, Dutch white clover, buckwheat, cowpea, lana vetch, 'Tropic Lalo' paspalum, and perennial peanut - Richard Ebesu, CES. Status: Completed. Location: James Nishida Jr. Farm (Private Farm, Kauai, HI)

4. Ground cover demonstration for weed control in papaya using perennial peanut, St. Augustine, carpetgrass - Dr. Joe DeFrank, UH Manoa. Status: Completed. Location: Poamoho Research Station (Experiment Station, O`ahu, HI)

5. Response of pineapple and nematodes to Telone EC applied in conventional and buffelgrass living sod production systems - Dr. Joe DeFrank, UH Manoa. Status: Completed. Location: Dole Foods Hawai`i Whitmore Village Facility (Private Farm, O`ahu, HI)

6. Cover crop and green manure trials for vegetable production - Dr. Hector Valenzuela, UH Manoa. Status: Completed. Location: Waimanalo Research Station (Experiment Station, O`ahu, HI)

7. Cover crop trials for orchard crops - Norman Nagata, CES. Status: Completed. Location: CES Maui Educational Garden (Community College, Maui, HI)

8. Sunn hemp trial for nematode control in edible ginger production - Dwight Sato, CES. Status: Completed. Location: Umauma Farm (Private Farm, Hawai`i Island, HI)

9. Sustainable alley cropping demonstration using leuceana and sunn hemp (with melia and neem extracts as insecticides) - Ray MacDuff NMCC. Status: Completed. Location: Kagman Experiment Station (Experiment Station, Saipan)

10. Cover Crops for nematode control in coffee - Virginia Easton Smith, CES. Status: Completed. Location: Kona area.

11. Azolla as a green manure in wetland taro - Roy Yamakawa, CES. Status: Completed. Location: Kobayashi Farm (Private Farm, Kaua`i HI).

Three demonstration sites were planned but not executed. Frank Cruz, Guam, was unable to actively participate in the project. We attempted to set up an alternate Guam demonstration project with Dr. Mari Marutani, however she too was unable to commit to a demonstration site on short notice. She did send an extension agent from Guam to attend the cover crop workshop. Ann Emmsley, Associate Professor at Maui Community College, had planned to have a green manure and cover crop trial, however was on maternity leave and unable to establish the project. Robin Shimabuku, plant pathologist and CES Agent on Maui, had planned a green manure trial to control pink root and fusarium basal plate rot in Maui sweet onion however the level of funding would not meet his requirements for a scientific research project. He is however conducting this research using alternate funding sources.

CES/NRCS TRAINING WORKSHOP: On October 5th-6th, 2000, we held the training workshop for the project. Attendance by both CES agents (12) and NRCS staff (13) was excellent, representing every Hawaiian island and Guam. The workshop included segments about the use of cover crops/green manures, a cover crop/green manure recommendation exercise, a computer exercise to use the web site database, classroom and field exercises in soil quality, and a visit to a cover crop/green manure demonstration site.

In alignment with the intent of the SARE Program, the workshop successfully represented a wide range of public and private sector agricultural interests. In attendance were teachers from Maui and Kauai Community Colleges, professors/staff from UH Manoa, an agricultural consultant, a commercial seed producer, a private sector agricultural researcher, organic farmers, plus 5 representatives from the Pacific region (Guam, Palau, Kosrae). The attendance of the Pacific Islanders was the result of our alliance with ADAP Project, which advertised the workshop to over 150 people in the Pacific Rim region. As a result, these 5 individuals arrived at our workshop using their own funding. Regrettably, we were unable to arrange to have our colleague from the Northern Marianas attend this meeting.

HAWAII AGRICULTURE 2001: Sustainable & Profitable AgriBusiness Today! (CONFERENCE): While not funded by this project, our state sustainable agriculture program was able to support a major statewide sustainable agriculture conference on January 26-27, 2001. The conference featured nationally recognized speakers such as Joel Salatin of Polyface Farm, Dr. Frank Zalom of the UC Statewide IPM Program, Claire Klotz of USDA Wholesale & Alternate Markets, and Dr. Yasuo Ohe of Chiba University (agritourism). In addition, locally recognized agricultural professionals and successful farmers and ranchers served as panelists and presenters. The conference featured several "threads" of interest -- major themes of sustainable agriculture: agroforestry, pastured animals, IPM, organic production, direct marketing, internet marketing, and agritourism. With over 200 participants, this conference represented the best and most innovative of Hawaii's sustainable agriculture industry.

Our program was able to establish valuable networking linkages and alliances as a result of this conference.

Information generated from this grant project about green manures, cover crops, and soil quality featured prominently in the well-attended IPM and organic production thread. A summary of the workshop can be found at:

MOLOKA`I SUSTAINABLE FARMING MINI CONFERENCE: As a result of both the cover crop grant and the January conference, CES agents and NRCS staff on Moloka`i teamed up to sponsor a local two day conference and field day. Held on June 15-16th, 2001, extension agents Alton Arakaki and Kali Arce joined forces to organize an excellent and well attended workshop for Moloka`i farmers. A special guest speaker, Bob Shaffer from Soil Culture Co. gave a keynote address on soil quality entitled "Living Soil." During the sessions about sustainable farming techniques, Robert Joy from the NRCS Plant Materials Center at Moloka`i gave a presentation about green manures and cover crops and discussed the SARE project in detail. Drs. Joe DeFrank and Hector Valenzuela from University of Hawaii at Manoa (both very active participants in this grant project) gave presentations on living mulch, trap crops, insectaries and biofumigation. Both Moloka`i CES agents presented the results of their demonstration projects to the community at the conference. An entire day was devoted to visiting and learning from farmers and ranchers on Moloka`i who use sustainable techniques. Associate professors from Moloka`i Community College and Kauai CC attended. Sheila Cox, NRCS District Conservationist for Moloka`i, attended the field day.

HOFA BODY AND SOIL CONFERENCE: One major goal for this year has been to improve and expand our interaction with the Hawaii Organic Farmers Association. We had a unique opportunity this year when HOFA sponsored a soil quality conference on Maui on July 18-19, 2001, inviting nationally recognized speakers Dr. Elaine Ingham (Soil Food Web, Inc.), Neal Kinsey (author of "Hands On Agronomy"), and Bob Shaffer from Soil Culture Consulting. This HOFA training program offered an exceptional hands-on field component. Organic farmers from Kauai, Maui, Hawaii Island and Oahu sent in soil samples ahead of time. With guidance from the trainers, attendees studied soil quality measurements and their relationships to cover cropping and other management practices. Three CES agents affiliated with this SARE project attended this event to expand their knowledge of soil quality and organic production techniques.

TOMATO PRODUCTION USING IPM IN THE WAIALUA FARMERS COOPERATIVE: On June 30th, 2001, Dr. John McHugh, a member of the Hawaii Farm Bureau Environmental Committee (and a private consultant with Crop Care Hawaii), held a field workshop on Oahu at the Vanna Farm in Waialua. The green manure/cover crop information from this SARE grant was featured as a major tool for sustainable production techniques. Three CES agents affiliated with our project (Dwight Sato, Hawaii Island, Norman Nagata, Maui, and Dale Sato, Oahu) attended this workshop. Dr. McHugh attended our October 2000 SARE cover crop/soil quality training and was one of the speakers for the IPM segment at the January 2001 conference. We plan to continue our alliance with this agricultural professional for future programs and projects.

HOFA ORGANIC TRAINING WORKSHOP: Although not funded by this grant, we feel it is important to mention that 8 of our CES agents attended a 3 day intensive training session in September held by HOFA (Hawaii Organic Farmers Association) to learn about organic certification requirements. This significant investment of staff time and resources represents a major signal that our extension staff is committed to learning more about sustainable agriculture.


Potential Contributions

Expanded use of Cover Crops

This project has stimulated interest in and use of cover crops around Hawaii and the Pacific. Researchers are reporting an increase in the use of crotalaria juncea in particular for increasing soil organic matter and reducing nematodes.

The Hawaii Farm Bureau Federation (environmental committee) is continuing research in the use of cover crops and they have obtained funding to conduct a cover cropping project with seed corn producers on Oahu.

Future Recommendations

The sustainable agriculture movement in Hawaii and the Pacific is slowly gaining momentum, spurred by the reality that island ecosystems are very vulnerable to environmental damage from agricultural chemicals and misuse of land resources. The demand for locally grown fresh food is growing, as is the demand for organic produce. Cover crops and green manures play a major role in sustainable production systems and are slowly becoming more commonly used.

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.