High nutrient solution fertilizers derived from local organic inputs for field and greenhouse application in the tropics

Project Overview

Project Type: Research and Education
Funds awarded in 2014: $170,466.34
Projected End Date: 12/31/2016
Region: Western
State: Hawaii
Principal Investigator:
Dr. Amjad Ahmad
University of Hawaii at Manoa

Annual Reports


  • Agronomic: corn
  • Fruits: melons, papaya
  • Vegetables: cabbages, peppers, sweet corn, tomatoes, turnips


  • Crop Production: food product quality/safety
  • Education and Training: extension, farmer to farmer, on-farm/ranch research, workshop
  • Farm Business Management: budgets/cost and returns
  • Natural Resources/Environment: biodiversity
  • Production Systems: organic agriculture, transitioning to organic
  • Soil Management: soil analysis, nutrient mineralization, soil microbiology, soil chemistry, organic matter, soil physics, soil quality/health
  • Sustainable Communities: partnerships, sustainability measures

    Proposal abstract:

    Replacing imported fertilizers with local resources is the highest research and educational priority identified by stakeholders throughout the Pacific at multiple meetings. While progress is being made in developing recommendations for locally produced solid fertilizers, the need for solution fertilizers derived from local resources has not yet been adequately addressed. This is especially true for growers of long-term food crops such as taro and fruit trees who need to provide supplemental nutrition throughout the cropping cycle. The production of locally derived nutrient solutions for fertigation will keep local farmers competitive, reduce water-use and loss, and protect the environment by reducing chemical use.

    Anecdotes from innovative growers and preliminary findings in the lab has shown that locally produced tankage (rendered meat, 9% N) was a good source of soluble nitrogen (NO3-N and NH4-N). At lab scale, some treatment effects on nitrogen release from tankage were tested. The preliminary results are promising, although there is a need to evaluate more treatments and increase scale in order to come up with recommendations for local farmers.

    The goal of this project is to develop capacity among Pacific Island growers to cost effectively produce concentrated nutrient solutions from local materials, accelerating current efforts to reduce grower reliance on imported fertilizers.

    The expected outcomes of this project are:

    *A measurable and significant reduction (> 10%) of local growers' reliance on imported soluble fertilizers and increase in Hawaii’s small farms' sustainability and profitability.
    *A validated model/procedure for developing a local nutrient solution that can be applied for other nutrients (P and K). *Enhanced capacity to educate and extend appropriate technologies and facilitate adoption among broader segment of growers.
    *Increased utilization of local, and relatively cheap, local inputs such as tankage, by 20% or more, by using it to produce soluble fertilizers.

    Project objectives from proposal:

    Objective 1: Identifying optimal temperature, time, chemical and biological factors to maximize mineralization and aqueous extraction of N from tankage.

    Activities: Develop and validate procedures to enhance the extracts of nitrate (NO3-N) and ammonium (NH4-N) from tankage using factors, such as: 1) Chemical and Biological (Baking soda, vermicompost, molasses, yeast). 2) Covering and aeration (cover/no cover, and aeration/no aeration). 3) Time and temperature (Time intervals 0-48 hours, and 20-35oC).

    Objective 2: Develop yield response curves and recommendations to optimize aqueous solution for greenhouse and field applications.

    Activities: Develop and validate greenhouse and field application recommendations to local farmers and producers through: 1) Series of greenhouse trials (to test quality of highest nitrogen soluble solution). 2) Series of on-farm trials (to evaluate laboratory and greenhouse trials results). 3) Evaluation of results (Develop greenhouse and field application recommendations).

    Objective 3: Disseminate the project findings among local producers, extension agents and other university professionals through a series of workshops and field days, extension bulletins, production procedure manual and other online resources.

    Activities include: Transfer the project findings among local farmers and other professionals through: 1) At least three on-farm workshops and field days to be conducted on different Hawaiian Islands (Oahu, Molokai and Big Island). 2) At least two Extension bulletins and a short manual for solution fertilizer production procedures. 3) At least two scientific peer reviewed publications.

    Note: Cost analysis of solution fertilizers production will be conducted throughout all activities.

    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.