Estimating the Application Rate of Locally Produced Liquid Organic Fertilizer to Meet Crop N Requirement

Project Overview

Project Type: Professional + Producer
Funds awarded in 2023: $74,547.00
Projected End Date: 08/31/2026
Grant Recipient: University of Hawaii at Manoa
Region: Western
State: Hawaii
Principal Investigator:
Dr. Amjad Ahmad
University of Hawaii at Manoa
Joshua Silva
University of Hawaii at Manoa, College of Tropical Agriculture a
Jensen Uyeda
University of Hawaii


  • Agronomic: corn
  • Fruits: avocados
  • Vegetables: okra


  • Crop Production: fertigation, organic fertilizers
  • Education and Training: on-farm/ranch research

    Proposal abstract:

    Replacing imported fertilizers with local resources is among the highest research and educational priority identified by stakeholders statewide. The need for N solution fertilizer derived from local resources has been fulfilled through a previous Western SARE award (SW14-026) and meant to be as a supplemental application. The recipe became very popular, especially among organic growers, and they call it “Tankage tea”. The growers currently are using the recipe as a main source of N for annual crops and fruit trees. However, there is a need to determine if the recipe is meeting crop N requirements for optimum yields or if excessive application is causing environmental pollution. The proposal aims to estimate N application rate using a new bio-mineralization filtering system which allows for a 1-week extraction period, instead of the old filtering system limited to only a 1-day extraction period. On-farm trials will be conducted using various crops. Solution and soil samples will be analyzed to determine nitrate, ammonium, and total N. This will allow us to calculate 1) N application over a crop growth period, 2) crop yield, and 3) soil fertility changes over 2-years period. On-farm field days and workshops will be conducted statewide to disseminate the project findings. Video demonstration of the system setup and extension bulletins with project results will be published online. This project is expected to benefit grower’s profitability and local food production sustainability, by providing the crops with required N, reducing nutrient losses, and improving soil health and fertility status.

    Project objectives from proposal:

    Objective 1) Estimating nitrogen application rate/load using locally made liquid organic fertilizer in on-farm trials.
    Objective 2) Measure crop growth and yield response to the use of liquid organic fertilizer as sole nitrogen source.
    Objective 3) Develop recommendations, video demonstrations, and educational materials for distribution statewide.
     Objective 4) Conduct field days and workshops to disseminate the project findings and increase adoption rate.
    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.