Grazing under Forest Plantations for Weed Control and Forage Production

Michael DuPonte, Extension Agent

Dr. James B. Friday, Extension Forester
Hawai'i Island

Forest plantations have been established on over 20,000 acres of former sugar cane lands in East Hawaii. A major problem in plantation establishment has been weed control, especially of guinea grass (Panicum maximum). The grass competes with the trees for moisture and nutrients, probably decreasing growth of the trees. Thick grass under trees also is also fuel and increases the risk of fires in the forest plantations. Guinea grass persists even under closed canopy forests in some areas. Currently forestry companies manage the grass with repeated applications of herbicides, which adds to management costs. Herbicide application also sometimes causes friction with neighboring farmers and residents.

At the same time, the cattle industry is seeking additional grazing lands to increase local production of forage-fed beef. Currently most cattle are shipped out of Hawaii for raising on the mainland. Efforts are underway to develop feedlots for finishing Hawaii-grown grass-fed beef. The missing link is pasture lands to raise stocker cattle. If cattle can be successfully grazed under tree plantations, a large forage resource will become available which will create new opportunities for Hawaii-raised livestock.

Internal and External Linkages
CTAHR: Cooperative Extension Service; Human, Food, and Animal Science; Natural Resource and Environmental Management
Private: Robert Sporleder, BETC Technologies; Forest Solutions, Kamehameha Schools

Target Audiences: Ranchers, forest plantation managers, landowners; CES Cooperative Extension faculty and other natural resources agency staff, including NRCS and DOFAW staff; private consultants.

Objectives: Demonstrate grazing of cattle under forest plantations as a means of weed control for forestry and a means of providing additional high-quality forage to the beef industry.

Plan of Work
1. Establish field site. Cooperate with Forest Solutions, a private consulting company, to select field site on land leased by PruTimber from Kamehameha Schools and currently planted with Eucalyptus grandis.
2. Design replicated trials with varied treatments (heavy graze, light graze).
3. Fence area.
4. Establish sub-plots for forestry measurements (50 trees each) and measure trees (diameter and height).
5. Fence area.
6. Graze cattle.
7. Conduct field day while cattle are grazing. Invite people from target audiences.
8. Re-measure trees.
9. Write report, extension leaflet, and website on project. (Models: CTAHR extension leaflets; CTAHR forestry extension website, CTAHR forages website).

Outputs: Hold field day with at least 5 natural resources extension professionals and 10 private landowners attending.
Produce extension leaflet and distribute to at least 50 landowners.
Produce extension website.

Outcomes: Cattle grazed under forest plantations on at least 500 acres.
Weed control costs decreased on areas grazed (500 acres).
Tree growth improved on areas grazed because of reduced weed competition.