Reducing Pacific Island Growers' Reliance on Off-island Fertilizer Sources Through Improved Awareness and Efficient Use of Local

Project Overview

Project Type: Research and Education
Funds awarded in 2011: $284,070.00
Projected End Date: 12/31/2015
Region: Western
State: Hawaii
Principal Investigator:
Dr. Theodore Radovich
University of Hawaii, Manoa

Annual Reports


Not commodity specific


  • Crop Production: municipal wastes, nutrient cycling, organic fertilizers, application rate management, tissue analysis
  • Education and Training: decision support system, extension, farmer to farmer, on-farm/ranch research, workshop
  • Farm Business Management: budgets/cost and returns
  • Production Systems: transitioning to organic, holistic management, organic agriculture
  • Soil Management: organic matter, soil analysis, nutrient mineralization


    Replacing imported fertilizers with local resources is the highest research, education, and development priority identified by the participants of the Western SARE Hawai’i Subregional conference held in Kona, Hawaii ( As commercial fertilizer costs increase with oil prices, a wide range of food producers in the Pacific region have become interested in locally available by-products that are suitable for use as agricultural inputs to improve crop health and productivity. These inputs include 1) commercial green-waste composts, 2) Rendered animal products (Tankage), and 3) invasive algae from coral reef remediation projects. Although readily available, there are several bottlenecks preventing effective use and adoption by local growers. These include: 1) commercial composts vary significantly in quality, often have low nitrogen content and frequently very high C:N ratio, 2) rendered meat product quality also varies depending on feedstock source, and we have yet to fully understand its effects on plant growth under different Hawaiian soils and microclimates, and 3) invasive algae is available in large quantity and can be an important source of K and other plant nutrients, but nutrient content depends on species, and potential salinity concerns need to be addressed. As a result, producers are unaware of resources available to them and unsure of their ability to profitably utilize the local resources they are aware of. This problem will be addressed via a series of greenhouse and on-farm trials in cooperation with university faculty, commercial growers, and industry partners.

    To address the proposed objectives and activities, the project team conducted the following:

    • Quality, maturity, nitrogen release pattern, and crop growth response for 10 different composts were evaluated through lab incubation and greenhouse trials using pak choi as a crop model. The results confirmed: 1) common quality parameters (C:N ratio and maturity) are not sufficient to evaluate the quality of a compost; 2) the rate of N mineralization from different organic amendments has a narrow range of 0.02–0.03/day; and 3) there is a potential for long-term improvement in soil fertility and quality due to compost applications, especially for composts contain 2% N and more.
    • Samples of major algae invasive species (Gracilaria salicornia, Kappaphycus alvarezii, and Eucheuma denticulatum) were collected periodically and we were able to: 1) establish bio-security protocol (drying the samples at 190OF for 72 hours) to ensure reduce viability of the invasive algae species into new locations in Hawaii; 2) confirm the K content in the three algae species were about 15-20% from samples collected over two years period; 3) establish an application rate of 200-250 lbs K/acre for sweet potato and pak choi crops form dried algae; 4) draw a K release pattern from different algae species under peat moss and different soils (results are still in the analysis stage); 5) MSc student was able to complete her degree using the project resources/materials (used the algae species under sweet potato crop).
    • Periodical (every 3 months) for over two years by now, Tankage (meat and bone meal by products) samples were collected from Island Commodities Co. We found: 1) average N content in the samples was 10%; 2) tankage can be a good source of other nutrient (such as P average 3%); 3) there is a chance of N loss from tankage between 10-15% annually of the initial N during storage, the decline depends on the storage condition, especially temperature and humidity; 4) in a lab leachate studies about 20% of total N was mineralized/released in the first two weeks of the incubation. Also, the total mineralized N after 90 days of incubation reached up to 75% of total N applied.

    Outreach activities were conducted to ensure distribution of the project findings among local farmers, extension agents, and other ag professionals: 1) three peer-reviewed articles were published so far and we are expecting more publications beyond the project durations; 2) two extension bulletins were published and we are expecting at least two more to be published in the near future; and 3) series of workshops/field days were conducted (please see public talks/presentations section for more details).

    Project objectives:

    1. Enhance the capacity of at least 300 growers, compost producers, and other agricultural professionals in Hawaii, American Samoa, and elsewhere to evaluate compost quality.
    2. Identify the most important variables influencing the effect of rendered meat products (tankage) on plant growth and mineral nutrition in Hawaii and American Samoa.
    3. Quantify the independent and interactive effect of species, collection location, and simple processing on nutrient content and availability of three algae species collected from multiple sites on Oahu, Molokai, and Hawaii islands.
    4. Ensure dissemination of information from this project to producers and agricultural professionals throughout the Pacific region beyond the project duration.

    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.