Progress report for SW23-955
Project Information
Integrated grazing of grasses and woody legume forages in Hawaii and the Pacific Basin has great potential to improve the sustainability of livestock production. Increasing local food production and reducing greenhouse gas emissions are twin goals of the State of Hawaii. Leucaena is a genus of multi-purpose N-fixing trees that has been used as a high-protein forage crop in the tropics and sub-tropics, but its reputation as an invasive species limits its use. The University of Hawaii has developed seedless hybrids of Leucaena, but there is no research on the productivity or forage quality of these hybrids in different environments. There are also no well-established and cost-effective methods to propagate and establish rooted plants in existing pastures, which producers identify as a serious barrier to adoption.
Our objectives for the research plan are (1) optimize and scale up vegetative propagation of seedless Leucaena hybrids, (2) evaluate (2) develop cost-effective practices to establish rooted cuttings of this hybrid in existing and new pastures to create a silvopasture system, (3) evaluate the productivity and forage quality of this silvopasture system in different climates and soil types, and (4) develop a financial model of Leucaena silvopasture in varying growing conditions. We will establish experimental trials on agricultural research stations to evaluate hybrid productivity, forage quality, and effects on soil organic matter under simulated grazing. Plant nurseries will adapt existing propagation methods for commercial-scale production. Agriculture and forestry operations firms will develop cost-effective outplanting practices for commercial-scale establishment. Results will allow for the development of a financial model to estimate costs and benefits of integrating Leucaena.
Our objectives for the education plan are (1) develop a project website and video channel to share general information and updates about the project; (2) host workshops and a field day to engage producers and other stakeholders to learn about interests, needs for adoption, demonstrate the silvopasture system in the field, and introduce the financial model; (3) develop videos and podcasts to complement workshop topics and interview researchers, extension experts, producers, and other stakeholders engaged in this project; and (4) produce scientific and professional research and extension presentations and publications on these topics.
The primary outcomes will be (1) efficient and large-scale propagation protocols, (2) effective establishment practices at a reasonable cost for producers that optimize forage productivity and quality for beef cattle production, (3) a working financial model that captures the range of costs and projected benefits of Leucaena silvopasture across a range of growing conditions.
The goal of this research is to demonstrate a viable silvopasture system with seedless Leucaena hybrids under a range of growing conditions. Our objectives for this project are to
- Optimize and scale up vegetative propagation of seedless Leucaena hybrids,
- Develop cost-effective practices to establish rooted cuttings of seedless Leuacena in existing and new pastures to create a silvopasture system,
- Evaluate the productivity and forage quality of this system in different climates and soil types, and
- Develop a preliminary financial model of Leucaena silvopasture in different climates and soil types.
The goal for this research cannot be fully accomplished with a single project. This initial project is intended to facilitate the ability to initiate grazing trials in a few years and to addresss the key barriers to adoption as identified by producers. These include the lack of supply of plant material at the scale needed for grazing, the uncertainty of how to effectively establish Leucaena in existing pastures, and concerns over the direct costs of establishment and the opportunity cost of taking grazing land out of production for the time it takes to establish Leucaena (expected to be one year).
Cooperators
- - Producer
- - Producer
- - Producer
- (Researcher)
- (Researcher)
Research
Objective 1: Optimize and scale Leucaena vegetative propagation
- We have propagated clones of Leucaena variety 'KX4-Hawaii' and shipped them to a cooperating nursery, Maui Native Nurseries. They are growing out these stock plants to use for vegetative propagation experiments that will mirror experiments we will conduct in a research nursery on Oʻahu. They will serve as the primary nursery evaluating the ability and cost to scale up propagation.
Objective 2: Leucaena silvopasture establishment
Waimanalo Site
- At the Waimanalo station, we 10 rows of variety 'KX4-Hawaii' in March 2023 and 8 rows of variety 'KX5-Hawaii' and 4 rows of variety '3-6' in August 2023. We are propagating other varieties to generate sufficient numbers of clones to plant in this site.
Other Sites
- Experimental areas were laid out at Kealia Ranch and Waiaha Ranch in October 2023.
- A contract to fence, prepare the sites, plant rooted cuttings of vareity KX4, and maintain the sites for one year was offered and accepted by Forest Solutions, a private forestry service company.
- Fencing of the experimental area at Kealia Ranch was completed in February 2024. Planting rows will be laid out and site preparation and planting will begin in May 2024.
- Rooted cuttings of variety KX4 were propagated for the Kealia site and are ready to be cut back, hardened off, and shippped to Hawaiʻi Island for planting.
- Rooted cuttings of variety KX4 are being propagated for the Waiaha site in time for planting when the site is prepared.
Objective 3: Silvopasture productivity and forage quality
- In April 2024, at the Waimanalo site we cut back stems of KX4 to a height of 50 cm in order to allow them to regrow. The fresh weight was measured separtely for the leaves plus green stems and for the woody stems of these trees. The diameter of the stems was measured as an indicator of regrowth potential.
- Samples were collected and dried to determine the water content and to estimate the dry weight equivalency of all the harvested material.
- Regrowth of sprouts on these trees will be monitored until the stems reach 5 mm in diameter. This is considered the maximum size and woodiness at which cattle will browse the material. Once this limit is reached, the material will be harvested, the fresh weight measured in the field, and the dry weight will be calculated from the samples taken in April 2024.
- The dried samples are now being prepared for preliminary analysis of forage quality and mimosine content, as described in the proposal. This will allow us to adapt and optimize standard lab methods for this type of material. Harvested material from regrowth of the stems will be the first set of data used for experimental analysis.
- Trees of varieties KX5 and 3-6 will be harvested in August and analyzed similarly to variety KX4.
Objective 4: Silvopasture financial model
- Costs for propagation and site preparation are being recorded by the PI and Forest Solutions for the Kealia and Waiaha Ranch sites. Costs for planting and site maintenance during the first year will also be included in the financial model.
Objective 3: Silvopasture productivity and forage quality
Table 1. Size and fresh weight of 1-year-old plants of variety KX4-Hawaii at the Waimanalo station
| Measurement | Average | Max | Min |
| Stem Diameter (cm) | 5.00 | 7.80 | 2.40 |
| Stem height above 50 cm (m) | 4.70 | 6.10 | 2.90 |
| Leaf + green stem wt (kg) | 2.15 | 4.78 | 0.64 |
| Woody stem wt (kg) | 6.26 | 16.78 | 0.09 |
Research Outcomes
Education and Outreach
Participation Summary:
Objective 1: Develop and maintain online resources and updates
- A website designer was hired to work with the co-PIs to develop a project website. An initial layout was designed, feedback was provided, and the final design was selected. Content for the website is now being added to the site prior to publishing it.
Objective 2: Hold workshops and field days for producers and professionals
- A producer interest workshop was held in March 2024. The meeting was held in person at the Palamanui campus of Hawaiʻi Community College on Hawaiʻi Island and remotely via Zoom. Presentations on the project research and education objectives were provided by co-PIs and shared via Zoom. A question-and-answer session was held after the presentations. A follow-up survey was sent out to attendees.
Objective 3: Project videos and podcasts
- In November 2023, the PI was interviewed by the two co-PIs who are extension agents and the co-hosts of the podcast Livestock Walaʻau to provide an overview of the project. This episode was published online and is publicly available for streaming.
Objective 2: Hold workshops and field days for producers and professionals
- The producer interest workshop was attended by seven individuals in person and 4 individuals online. One producer-couple expressed interest in serving as a cooperating producer for this project.
- Outreach by Forest Solutions to another producer resulted in an expression of interest in also serving as a cooperating producer. The PI and the producer are scheduling a visit to their ranch to view potential sites and discuss how they can cooperate in the project.
Objective 3: Project videos and podcasts
- The Livestock Walaʻau podcast episode has been downloaded/listened to 32 times so far: nine from places other than the US. A producer who listened to the podcast episode on Livestock Walaʻau of the PI providing an overview of the project later reached out to the PI to discuss their family's experience using seeded varieties Leucaena for silvopasture in Central America. The PI and the producer are planning follow up conversations to discuss possibilities for cooperation using seedless varieties of Leucaena.