Evaluation and implementation of nitrogen fixing species in hedgerow intercropping in Marianas

Final Report for SW99-048

Project Type: Research and Education
Funds awarded in 1999: $132,000.00
Projected End Date: 12/31/2003
Matching Non-Federal Funds: $21,000.00
Region: Western
State: Guam
Principal Investigator:
Mari Marutani
College of Nat. & Appl. Sciences, Univ. of Guam
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Project Information

Abstract:

A comparison of field performance of nitrogen fixing trees (NFTs) in Guam determined that biomass production was greatly influenced by soil types and plant species. The plants in the study included Acacia angustissuma, Cajanus cajan, Calliandra calothyrsus, Desmodium rensonii, Gliricidia sepium, Flemingia macrophylla, Leucaena leucocephala cv. K636, and Sesbania sesban cv. Nubica. Leucaena leucocephala was the most adapted NFT to calcareous soil, a dominant soil type in northern Guam. Flemingia macrophylla was adapted to acidic soil. Video and pamphlets on plant propagation and management were produced and distributed to the community in Guam and the Commonwealth of Northern Mariana Islands.

Project Objectives:

(1). Develop a protocol for seed propagation methods of leguminous hedgerow plants and produce a propagation guidebook.
(2). Examine biomass production of leguminous hedgerow plants grown in different soil regimes on Guam.
(3). Examine seed production of leguminous hedgerow plants grown in different soil regimes on Guam.
(4). Examine susceptibility of leguminous hedgerow plants to arthropod, nematode, and disease problems.
(5). Produce educational publications of plant management of nitrogen fixing trees (NFTs).

Introduction:

Leguminous nitrogen fixing trees (NFTs) provide many benefits to tropical island farming systems in the western Pacific. Hedgerow intercropping with NFTs, as an example, prevents soil erosion, provides a barrier for disease and pest spread, and suppresses weeds by mulching with leaf litter generated by NFTs. This project consisted of two components, research and education, to demonstrate usefulness of NFTs in the agroecosystem of the Mariana Islands.
One of the research projects determined adaptability of NFTs to different soil regimes on Guam. The result of this study indicated that fresh biomass production was greatly influenced by soil types as well as plant species. Leucaena leucocephala K636 was the most adapted NFT to calcareous soil (Lithic Ustorthents) that is a dominant soil type in northern Guam. The main troublesome pests on NFTs on Guam were arthropods such as mealybugs (Ferrisia virgata?), Chinese rose beetle (Adoretus sinicus), and longhorn beetle (Prosplus branchii). No serious foliage, stem, and floral diseases were observed on all NFTS at all locations during the experiment. Selected NFTs were also evaluated for their palatability to goats at a farmer’s ranch. It was found that Leucaena leucocephala, Desmodium rensonii, and Cajanus cajan are more palatable than Gliricidia sepium.
The comparison of biomass yield of eight NFTs was presented at the 10th Inter-Congress of the Pacific Science Association: Sustainable Agriculture during June 1-6, 2001. The result was also published as a research paper in the proceedings of Sustainable Agriculture in the Pacific and Asian Region and as a fact sheet for the local community.
A video and pamphlets on plant propagation and management of NFTs were produced and distributed to local high schools and USDA-NRCS offices in Guam and the Commonwealth of Northern Mariana Islands.

Research

Materials and methods:

Objective 1: Develop a protocol for seed propagation methods of leguminous hedgerow plants and produce a propagation guidebook.
Seeds of eight selected nitrogen fixing leguminous plants (NFTs) were obtained locally or from a seed company in Hawaii. The plants in the study included Acacia angustissuma, Cajanus cajan, Calliandra calothyrsus, Desmodium rensonii, Gliricidia sepium, Flemingia macrophylla, Leucaena leucocephala cv. K636, and Sesbania sesban cv. Nubica. Seed and vegetative propagation methods were reviewed for each species.

Objective 2: Examine biomass production of leguminous hedgerow plants grown in different soil regimes on Guam.
Guam is located at 144°55’E longitude and 13°33’N latitude, and has monthly average temperature ranging from 22 °C to 30 °C. Eight NFTs were studied for their biomass production at three soil regimes. They were Acacia angustissuma, Cajanus cajan, Calliandra calothyrsus, Desmodium rensonii, Gliricidia sepium, Flemingia macrophylla, Leucaena leucocephala cv. K636, and Sesbania sesban cv. Nubica. The field trials were conducted at three Experiment Station farms: Yigo farm with the soil characterized as Guam cobbly clay loam (clayey, gibbsitic, nonacid, isohyperthermic Lithic Ustorthents) with pH of 6.4- 7.5, Barrigada farm with the soil type of Pulantat clay (clayey, montmorillonitic, isohyperthermic, shallow Udic Haplustalfs) with pH of 6.0-7.5, and at Ija farm with Akina silty clay (very fine, kaolinitic, isohyperthermic Oxic Haplustalfs) with pH of 4.5-6.2. Three-month-old NFT seedlings were transplanted in July 2000 for testing the biomass production from November 2000 to July 2001. At each location an experiment was conducted in randomized complete block design (RCB) with three replications. The size of a plot was 2 m x 2 m. Four seedlings of each NFT species were planted in a row for each plot with the distance of 0.5 m between plants. The top canopy including leaves and stems of each NFT was cut at the height of 76 cm from the ground once a month. Total fresh biomass harvested was compared.

Objective 3: Examine seed production of leguminous hedgerow plants grown in different soil regimes on Guam.
Seed production of eight NFTs was examined monthly. Adjacent to the NFT biomass production test plot (in Objective 2), representative plants of each species were examined for their flower and seed production at all three locales. The results of flowering and seed production were summarized.

Objective 4: Examine susceptibility of leguminous hedgerow plants to arthropod, nematode, and disease problems.
The NFTs grown for the field evaluation in Objective 2 were examined monthly for the occurrence of arthropods, diseases, and nematodes. If plant damages were found, the samples were investigated carefully under a microscope to identify the pests.

Objective 5: Produce educational publications on plant management of nitrogen fixing trees (NFTs).
The video entitled “Nitrogen Fixing Trees in the Marianas,” and a series of pamphlets of eight nitrogen fixing trees including Acacia angustissuma, Cajanus cajan, Calliandra calothyrsus, Desmodium rensonii, Gliricidia sepium, Flemingia macrophylla, Leucaena leucocephala cv. K636, and Sesbania sesban cv. Nubica. were produced. A commercial video producer was contracted to create the video based on out script.
Pamphlets were created using a desk-publishing software. A commercial printing company printed publication and their PDF formats were prepared as electronic publication.

Research results and discussion:

Objective 1: Develop a protocol for seed propagation methods of leguminous hedgerow plants and produce a propagation guidebook.
Recommended plant propagation methods were presented as a pamphlet for each species.
1. Acacia angustissuma: Direct sowing; increased seed germination results from soaking seeds in water for 6 hours at room temperature prior to planting.
2. Cajanus cajan: Direct sowing; increased seed germination results from soaking seeds in water for 24 hours at room temperature prior to planting.
3. Calliandra calothyrsus: Direct sowing; increased seed germination results from soaking seeds in hot water for 3 min, and then soaking in water for 24 hours at room temperature prior to planting.
4. Desmodium rensonii: Direct sowing.
5. Flemingia macrophylla: Direct sowing; increased seed germination results from soaking seeds in hot water for 3 min. or from soaking seeds in sulfuric acid for 15 min. prior to planting.
6. Gliricidia sepium: Stem cuttings or direct sowing; increased seed germination results from soaking seeds in water for 24 hours at room temperature prior to planting.
7. Leucaena leucocephala cv. K636: Direct sowing; increased seed germination results from soaking seeds in sulfuric acid for 30 min. prior to planting.
8. Sesbania sesban cv. Nubica: Direct sowing; increased seed germination results from soaking seeds in water for 24 hours at room temperature prior to planting.
A brochure describing the propagation methods for each species was produced.

Objective 2: Examine biomass production of leguminous hedgerow plants grown in different soil regimes on Guam.
All NFTs except F. macrophylla and C. calothyrsus yielded more than 11 t ha-1 of biomass at Barrigada. L. leucocephala cv. K636 had the highest yield in alkaline soils at Barrigada (26.1 t ha-1) and at Yigo (12.3 t ha-1). In acidic soil at Ija F. macrophylla (6.6 t ha-1) produced the greatest biomass. The experiment indicated that growing soil type and plant species affected the production of biomass.

Objective 3: Examine seed production of leguminous hedgerow plants grown in different soil regimes on Guam.
Desmodium rensonii and Flemingia macrophylla produced numerous seeds regardless of seasons. In contrast, Leucaena leucocephala and Sesbania sesban produced more seeds in alkaline soils of Barrigada and Yigo than in acid soils of Ija. Acacia angustissima and Cajanus cajan had good seed production in Barrigada, whereas at both Yigo and Ija sites, there were no or very few seeds produced. Calliandra calothyrsus produced very few seeds at all. Only one flower and a pod of Gliricidia sepium was observed only at Barrigada.

Objective 4: Examine susceptibility of leguminous hedgerow plants to arthropod, nematode, and disease problems.
The main troublesome pests on leguminous hedgerow plants were arthropods such as mealybugs (Ferrisia virgata?), Chinese rose beetle (Adoretus sinicus), and longhorn beetle (Prosplus branchii). No serious foliage, stem, and floral diseases were observed on all NFTS at all locations. None of NFTs in Yigo were affected by the root-knot nematode (Meloidogyne spp), although the soil at the Yigo Experiment Station is known to be infested by the pathogen.

Objective 5: Produce educational publications on plant management of nitrogen fixing trees (NFTs).
A 15-min video production on plant management of NFTs was completed in April 2003. Duplicates of the video along with eight pamphlets were distributed to a community in the Marianas. The video is entitled “Nitrogen Fixing Trees in the Marianas,” and a series of pamphlets of eight nitrogen fixing trees include Acacia angustissuma, Cajanus cajan, Calliandra calothyrsus, Desmodium rensonii, Gliricidia sepium, Flemingia macrophylla, Leucaena leucocephala cv. K636, and Sesbania sesban cv. Nubica.

Research conclusions:

Nitrogen fixing trees (NFTs) provide many benefits to tropical island farming systems in the western Pacific. Hedgerow intercropping with NFTs, as an example, prevents soil erosion, provides a barrier for disease and pest spread, and suppresses weeds by mulching with leaf litter generated from NFTs. This farming operation would help reduce usage of fertilizers and pesticides that potentially contaminate the island environment.
The project provided information on selection of NFTs suitable to different soil types on Guam. The study result indicated that fresh biomass production was greatly influenced by soil types as well as plant species. Leucaena leucocephala K636 was the most adapted NFT to calcareous soil (Lithic Ustorthents), which is a dominant soil type in northern Guam. In the central part of the island with Udic Haplustalfs soil, most of eight NFT species performed very well. In contrast in Oxic Haplustalfs soil of southern Guam, most NFTs yielded poorly. Selection of NFTs suitable to a farm is the key step in sustainable farming operation.
Findings were disseminated as a technical publication and as a fact sheet, pamphlets, and a video. First, the result of comparison study on biomass yield of eight NFTs was presented at the 10th Inter-Congress of the Pacific Science Association during June 1-6, 2001. The SARE project co-sponsored the Sustainable Agriculture session during the conference. The result was also published as a research paper in the proceedings of Sustainable Agriculture in the Pacific and Asian Region. One-page fact sheet disseminated the finding to local community.
The video and pamphlets on plant propagation and management of NFTs were produced and distributed to local high schools, Guam Cooperative Extension Service, and USDA-NRCS offices in Guam and the Commonwealth of Northern Mariana Islands. Marianas Cable Vision kindly broadcasted the video in Saipan in October 2003.
The plant specimens of eight NFTs are being maintained for observation purpose and as conservation of these plant genotypes at three Agricultural Experiment farms, Yigo, Barrigada, and Ija.

Participation Summary

Educational & Outreach Activities

Participation Summary:

Education/outreach description:

I. Publication:
Marutani, M. and P. Sablan. 2001. Selecting nitrogen fixing trees suitable for your soils. Agfaxts: Horticulture and Environmental Sciences. 2001-2. University of Guam. 1p.
Sablan, P. and M. Marutani. 2003. Nitrogen fixing trees suitable for diversified soils on Guam. In the Proceedings: Sustainable Agriculture in the Pacific and Asian Regions. Micronesica Supplement 7: 69-75.
Sablan, P. and M. Marutani. 2003. A series of pamphlets of eight nitrogen fixing species.
(a). Acacia angustissuma
(b). Cajanus cajan
(c). Calliandra calothyrsus
(d). Desmodium rensonii
(e). Flemingia macrophylla.
(f). Gliricidia sepium
(g). Leucaena leucocephala cv. K636
(h). Sesbania sesban cv. Nubica

Sablan, P. and K. Perez. 2001. Nitrogen fixing trees suitable for diversified soils on Guam. (Abstr). In Proceedings: The Integration of Natural and Social Sciences in the New Pacific Millennium. The 10th Pacific Science Inter-Congress. p.24. A poster presentation.

2. Video Production:
Marutani, M. and P. Sablan. 2003. Nitrogen Fixing Trees in the Marianas. (15 min)

Project Outcomes

Project outcomes:

This research/education project did not have a component of cost analysis of the technology.

Farmer Adoption

Selected NFTs were planted at two farmers' fields to screen species adapted to the soil type. For both farms the main purpose of NFT planting was to feed goats. The project had a direct impact on delivering information on usefulness of NFTs, however farmers tended to depend on plant maintenance including weeding and irrigation to the University personals. Conducting a trial at a farmer’s field was advantageous to have immediate farmer’s adoption of technology if the trial was successful.
At the planning stage of the demonstration/test trial, farmers expressed strong interest in the project. They could observe plant characteristics of newly introduced NFTs in their fields
The official agreement was made with participating farmers stating the role of direct farmer involvement. However, during the trial at the farmers' fields their involvement was minimal and limited to exchanging information on the project. After the project, the farmers continue to maintain NFT plants in their fields and will use them as multipurpose plants.

Recommendations:

Areas needing additional study

Erosion control study using NFTs was explored during the project in the highly eroded southern part of the island. Selected NFTs were planted at two sites with southern soil with slopes. The future study will need to periodically measure the depth of soil accumulation and the loss of soil to evaluate effects of NFTs on erosion control. The present study found only few NFTs adapted in the southern acidic clayey soils. New germlines can be evaluated for their adaptation to this soil type and whether amending the soils with lime will improve plant growth.
New germlines of Leucaena spp. are available from the University of Hawaii leucaena breeding program and other NFT seed companies. New Leucaena spp. need to be tested to improve their field performance in calcareous soil.
More efficient ways to disseminate educational materials generated by the Western SARE project need to be identified. Many farmers are retirees and part-timers on Guam. When actual laborers engaging farming are non-English speakers, a lack of communication becomes the first barrier to a technology transfer system.

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.