Covering New Ground: Tropical Cover Crops for Improving Soil Quality

1998 Annual 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

Covering New Ground: Tropical Cover Crops for Improving Soil Quality



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.
3. Make cover/green manure crop information accessible in print, CD ROM, and a Web-based database.
4. Establish 10 cover crop demonstration sites representing different tropical crops and cropping systems to gain experience and prepare for future field days for the public.
5. Carry out Cooperative Extension Service (CES) and Natural Resources Conservation Service (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.
6. CES Agents apply their knowledge by conducting cover crop training for the public via field days at demonstration sites.


At this relatively early stage of the project (eight months), major outcomes have been realized in the following areas:
1. The project has heightened awareness of the need for and use of cover crops primarily for CES extension agents and to a lesser degree for agricultural educators and agricultural producers. An initial set of approximately 25-30 suitable cover and green manure crops for the tropics has been identified (5-10 more crops than proposed originally).
2. Draft plant descriptions for approximately 23 cover crops and green manures have been prepared and will soon be posted on a web site for review and comment by the Work Group.
3. Initial training in cover crops has been conducted with CES agents, NRCS and the general public a workshop at the University of Hawai`i Poamoho Experiment stations (papaya cover crop demonstration site).
4. Requests for 12 demonstration sites have been received (with funding for only 10 available). These demonstration sites represent various cropping systems and tropical crops. They are in various stages of review, approval, and installation.

Specific Results

The work group was formally established and communications began in May 1999. Five additional CES agents have joined the Work Group, further expanding support for the project by university agricultural professionals. One Work Group meeting has been held and it maintains good communication via e-mail.

Agricultural commodity groups (representing major crops of Hawai`i) were contacted and invited to participate. To date, approximately 15 farmers have returned written surveys and their initial responses indicate strong interest on the part of the farming community in cover crops and green manures.

Agricultural educators at Community Colleges and high schools on O’ahu, Maui/Molokai, Hawai`i, and Kauai were contacted in July and again in October and invited to participate. Teachers at Maui and Kauai Community Colleges are very interested in the project. The participation of these agricultural educators has potentially greatly expanded the network and impact of the grant project.

Communication with participants on Guam and the Northern Marianas has proven to be difficult. To date we have received relatively little feedback from them. We would like to improve these lines of communication in the upcoming months of the project. We are also strengthening our ties to the Agricultural Development in the American Pacific (ADAP) Project. The 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. We have solicited research information on Pacific Island cover/green manure crops from this group

The Hawai`i Organic Farmers Association has expressed long term interest in promoting and supporting the project.

A workshop about using cover crops in papaya orchards was held at the University of Hawai`i Poamoho Experiment Station. Approximately 33 people attended, of those eight were CES agents and three were NRCS employees. The workshop was advertised in the newpaper and on the Sustainable Agriculture in Hawai`i Web site ( The Web site also features some initial cover crop plant descriptions on-line.

The process of choosing a set of suitable cover crops and green manures was slow due the process involved in determining crop selection criteria. A list of approximately 25-30 crops (based on Hawai`i NRCS Tech Guide recommendations) are currently proposed (subject to review and change). The work group opted to limit recommended plants to species with a proven track record in Hawai`i and the Pacific, plants that are readily obtainable (seed source or planting material), and plants that are not considered potentially noxious weeds by the Hawai`i state government. Some temperate crops meet these criteria and are included in the list.

Plant descriptions modeled on the UC Sustainable Agriculture Research and Education Program (UC SAREP) cover crop database are being written for these crops (about 23 crops are at a first draft stage). If a temperate plant is already described on the UC SAREP database, the plant description will be abbreviated and UC SAREP will be referenced for further information. We project that preliminary plant descriptions for 25 crops will be on-line for review by the end of February.

An initial literature search for tropical cover crops has been conducted. Preliminary contacts with international agricultural centers have been made as well.

Interest in conducting cover/green manure crop demonstration sites has been high among CES agents. The grant project has afforded us the opportunity to introduce CES agents and NRCS staff to several new cultivars of cover/green manure crops that are nematode resistant, a highly desirable attribute in a tropical environment. Nematode resistant black oats, alfalfa, rapeseed, rhodes grass, and a sorghum-sudangrass hybrid are currently being evaluated by CES staff in Hawai`i.

Preparations for the upcoming three-day workshop are in their very earliest stages. We have received initial commitments from soil scientists from the UH Department of Agronomy and Soil Science and from the Hawai`i NRCS for the soil quality training segment.

Potential Benefits

We can already discern an increased interest on the part of producers for information about cover/green manure crops, as a result of the initial contacts made while introducing the project and the two workshops offered.

CES agents are beginning to contact our offices with questions about cover/green manure crops. Little has been done with cover/green manures in the past and without field experience, CES agents and producers are reluctant to adopt their use. With the advent of the demonstration sites and the written and Web-based information, we envision greater adoption of these proven cropping methods. NRCS staff is more familiar with the use of cover/green manure crops but welcome the introduction of new cultivars and information sources to assist them in improving their recommendations to their clients.

This summary was prepared by the project coordinator for the 2000 reporting cycle.


Dr. Hector Valenzuela
Vegetable Specialist
University of Hawai`i at Manoa
3190 Maile Way
Room 102
Honolulu, HI 96822
Office Phone: 8089568351
Dr. Scott Campbell
University of Hawai`i at Manoa
3190 Maile Way
Room 102
Honolulu, HI 96822
Office Phone: 8089568351
Robert Joy
Plant Materials Specialist
USDA Natural Resources Conservation Service
Plant Materials Center
PO Box 236
Hoolehua, HI 96729
Office Phone: 8085676885
Dr. Joe DeFrank
Weed Specialist
University of Hawai`i at Manoa
3190 Maile Way
Room 102
Honolulu, HI 96822
Office Phone: 8089568351
Jody Smith
Education Specialist II
University of Hawai`i at Manoa
1910 East West Rd. Sherman Lab
Honolulu, HI 96822
Office Phone: 8089568708
Ray MacDuff
Northern Marianas College
Agriculture and Life Sciences
PO Box 1250
Saipan, MP 96950
Lisa Ferentinos

Education Specialist II
University of Hawai`i at Manoa
1910 East West Rd. Sherman Lab
Honolulu, HI 96822
Richard Ebesu
CES Agent
CTAHR University of Hawaii
CES Kauai Office
3060 Eiwa Street #210
Lihue, HI 96766
Office Phone: 8082743471
Frank Cruz
University of Guam
College of Agriculture and Life Sciences
UOG Station
Mangilao, GU 96923
Larry Shinshiro
State Agronomist
USDA Natural Resources Conservation Service
300 Ala Moana Blvd. Rm #4-118
Honolulu, HI 96850
Office Phone: 8085412600
Alton Arakaki
CES Agent
CTAHR University of Hawaii
CES Molokai Office
PO Box 394
Hoolehua, HI 96729
Office Phone: 8085676934