Improving Nitrogen Synchronization of Local Fertilizers, Soil Fertility, and Crop Quality with Biochar Application

Project Overview

Project Type: Research and Education
Funds awarded in 2016: $259,816.00
Projected End Date: 12/31/2019
Grant Recipient: University of Hawaii at Manoa
Region: Western
State: Hawaii
Principal Investigator:
Dr. Nguyen Hue
University of Hawaii at Manoa

Annual Reports


  • Nuts: papaya
  • Vegetables: cabbages, eggplant


  • Crop Production: organic fertilizers, tissue analysis
  • Education and Training: demonstration, extension, on-farm/ranch research, workshop
  • Farm Business Management: value added
  • Natural Resources/Environment: carbon sequestration
  • Production Systems: organic agriculture
  • Soil Management: soil analysis, nutrient mineralization, soil chemistry, soil microbiology, organic matter, soil physics, soil quality/health

    Proposal abstract:

    Replacing imported fertilizers with local resources is the highest research and education priority identified by stakeholders in Hawaii and other Pacific Islands. While progress is being made in developing recommendations for locally produced fertilizers, the innovative use of biochars to reduce nitrogen (N) loss from organic fertilizers (during storage and pre-application), enhance N mineralization, improve and sustain soil quality and fertility, and increase crop growth, yield, and quality has not been adequately addressed. Our lab results of N analysis in tankage (meat and bone meal by-products averaging 10% N) samples showed a significant continuous decline in N content during storage. The N loss could reach 30% of the initial N content. Under field/farm condition, the decline is expected to be higher and faster due to optimum conditions (e.g. temperature and rainfall) for the decomposition under the tropical climate. That would pose a potential financial loss to farmers as well as a potential contamination to the environment. Biochars could mitigate these adverse effects. Biochar is the solid material that is formed by decomposing biomass at elevated temperatures in the absence of oxygen in a process known as pyrolysis. Biochar is a promising soil amendment that has been shown to increase soil productivity and crop production in certain cases. The approaches used include: 1) biochars produced locally in Hawaii (from the Big Island) will be mixed (at 0, 2, 4, and 8% by weight) with high-N organic fertilizers (e.g., meat-fish waste called tankage, Sustain, Bioflora) to control N losses. Total N, NH3 gas, NH4, NO3, pH, EC of the mixtures will be monitored every 3 months up to 2 years. Optimal percentage of biochar/fertilizer combination will be identified. Such formulation will be tested on a peat medium and on selected agriculturally important soils of Hawaii, using a fast growing vegetable (e.g., Chinese cabbage) as the test crop. From the results of these experiments, sound recommendations regarding biochar/fertilizer combination will be developed and publicized. 2) Upon biochar/organic fertilizer applications, soil quality will be evaluated. Parameters tested include biological (CO2 release, microbial enzymes, microbes and fungi counts), chemical (pH, CaCO3 equivalent, CEC, available nutrients [mainly total C and N, inorganic N, extractable P, K, Ca, etc.], and physical (soil bulk density, water holding capacity, aggregate size). Both greenhouse and field trials will be utilized. 3) Effects of biochar/fertilizer combination on growth, yield, and quality of selected crops (vegetables such as Chinese cabbage, eggplant, and seedlings of trees such as papaya, coffee) will be determined. Plant height, leaf area, chlorophyll and nutrient contents are among the parameters measured. 4) The project findings will be disseminated among local producers, extension agents, and other university professionals. At least three on-farm workshops to be conducted on different Hawaiian Islands to transfer the project findings to the local community. At least three Extension bulletins will be developed and distributed among local farmers. The bulletins will focus on the benefits of using biochar and organic fertilizer combinations to soils and crops, and economical benefits to farmers. Websites to which materials will be posted include: SOAP:; eXtension: At least two scientific peer reviewed publications to be produced (probably during the last two years of the project) based on the data collected from laboratory, greenhouse, and field trials.

    Project objectives from proposal:

    The objectives of this project are to evaluate the short- and long-term effects of biochar applications to (or along with) different organic fertilizers (and soils) on:

    1) N content changes over time from the organic fertilizers during storage, N mineralization rate, and N use efficiency in different soils;

    2) Changes in biological, chemical, and physical characteristics of the applied soils (soil quality);

    3) Crop growth and yield in response to biochar-organic fertilizer applications.

    4) Dissemination of the project findings to local farmers, extension agents, and peer professionals.

    Some expected outcomes of this project are:

    1) Proper and beneficial use of local organic fertilizers along with biochar by farmers in Hawaii;

    2) Increased fertilizer use efficiency, especially N; and

    3) Increased growers’ profitability while protecting the environment.

    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.