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 (http://wsare.usu.edu/conf/hi/docs/NeedsIssues.pdf). 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).
- Enhance the capacity of at least 300 growers, compost producers, and other agricultural professionals in Hawaii, American Samoa, and elsewhere to evaluate compost quality.
- Identify the most important variables influencing the effect of rendered meat products (tankage) on plant growth and mineral nutrition in Hawaii and American Samoa.
- 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.
- Ensure dissemination of information from this project to producers and agricultural professionals throughout the Pacific region beyond the project duration.
Soils rarely have sufficient nutrients, such as N, P, and K, for crops to reach their maximum yield. Therefore, farmers apply soil amendments, including commercial or organic fertilizers that are rich in nutrients to ensure increased crop productivity. (Abbasi and Adams, 2000) The addition of organic matter to the soil may also improve soil structure, aeration, soil water holding capacity, and water infiltration (Yu-hong et al, 2005) and is considered an agronomically feasible and economically viable manure disposal option (McCann et al., 2005 and Kuo, et al, 2004). Pacific islands import over 85% of the food consumed and have less than a seven day supply of food on hand at any given time. At the same time, the cost of imported fertilizers increased from $300 to $1,000 per ton between 2006 and 2008, which increased the demand for local organic fertilizers in order to keep local producers competitive. Improved food security in the Pacific islands requires that a cost effective, stable source of local fertilizer be available to growers. Compost, meat meal, and seaweeds are promising, local organic sources of nutrients, although information about their performance in Pacific island soils and conditions is lacking, and specific challenges in using each of these products exists. Compost maturity and stability are important concepts of compost quality that many growers (and some compost producers) are unclear on. Although interconnected, “Maturity” generally refers to the ability of composts to effectively promote plant growth in the short term, while “Stability” is associated with microbial activity in composts. The maturity and stability of composts is difficult to differentiate, and the use of immature/unstable composts without proper adjustment may result in inefficient nutrient use and poor plant growth in the short term, consequently leading to less use of any compost in the future by risk adverse growers (Hue and Liu, 1995).
Common measures of compost stability and maturity include CO2 evolution and the ratio of Carbon to Nitrogen (C:N), respectively. These measures are best conducted in the lab, requiring time and considerable expense, making them impractical measures for growers to use effectively to evaluate the compost that they receive or produce. Also, batch-to-batch variability makes it important for commercial compost producers to monitor quality at a frequency that makes shipment of samples off-site challenging. Rapid, on-site measures of quality are available and include self heating tests to determine stability, and germination tests to evaluate maturity. Rapid methods to measure compost quality have not been validated across the wide range of composts produced in the American Pacific, resulting in low awareness and poor adoption of these promising technologies.
Rendered products (tankage) produced in Hawaii and American Samoa from fish and other meat waste generally have high N (9% dry weight) and low C:N ratio (5:1) making it a very important source of readily available organic nitrogen, and some phosphorous (2.5%). Although used by some growers, the quality of rendered meat products, the pattern of nutrient release from them over time, and crops response to different applications, particularly in tropical Pacific soils, has only been addressed by a few studies (Valenzuela et al. 2000; Arakaki 2008).Consequently, the value of tankage as an agricultural input is still poorly understood.
Invasive algae species have become a serious problem on reefs in the tropical Pacific, as they effectively compete for oxygen and sunlight, killing corals and replacing valuable seaweed used for food by fish and people (EPA, et al, 2004). Sustained efforts to remove the algae by various groups has produced millions of pounds of the material that must be disposed of. Efforts to compost the material and/or apply it directly to fields indicate that invasive and cultured algae can contribute to plant nutrition (particularly potassium (K)) and growth. However, preliminary analyses indicate that mineral nutrient and heavy metal content of these algae differ dramatically by species (some have almost no K) and location of growth. Our knowledge of the variation in nutrient, salt, and heavy metal content of the material among species at different locations must be improved in order for growers to effectively utilize this promising source of local, organic potassium and micronutrients.
This project engaged farmers, researchers, and industry professionals in order to address these challenges, through a series of lab, greenhouse, and on-farm trials and educational activities in a broad range of tropical island environments. The potential benefits of local produced fertilizers are substantial and are particularly relevant to agricultural production in tropical island environments because they promote of reduced reliance on off-island inputs, environmentally sound waste management to protect watersheds and reefs, and improved profitability of small and mid-sized farm that predominate large farms in these areas.
Objective 1 (Year 1-2)
Activity 1: Determine quality variation using standard measures
At least twenty different local commercial composts were collected from Hawaii and Samoa and quality was evaluated for CO2 evolution, pH, C to N ratio, NO3 and NH4, and mineral nutrient content using standard protocols (Hue and Liu, 1995). Focus was on thermal green waste-based commercial composts because these are produced in greatest amounts and exhibit the tendency for challenges associated with high C:N. Other local thermal and worm based composts derived from animal manures, food waste and biosolids were also evaluated for comparison.
Activity 2: Validate rapid measures against standard measures
The quality characteristics above were correlated with the self heating test (Dewar standard method), as described by Brinton et al (1995). Bioassays for plant germination were conducted using multiple species (e.g. cress, cucumber). Producers listed in this project agreed to participate in this activity to evaluate the ease and efficacy of these rapid measures on local composts.
Activity 3: Field trials
Replicated on-farm trials were conducted with three producers (Mohala farms, Poamoho Produce, Gurr farms). Immature and/or low N composts (high C:N) were adjusted with local high N sources, to procure multiple C:N ratios (e.g. 10:1, 20:1 and 40:1. Adjusted and unadjusted composts were evaluated for impact on vegetable yield. Data was analyzed using appropriate statistical software.
Objective 2 (Year 1-3)
Activity 1: Determine tankage variability in mineral nutrient and fatty acid content
A nutrient profile was conducted on tankage samples collected from a local supplier over a period of time. Samples were analyzed for nutrients and phytotoxic fatty acids (Pérez-Juan et al. 2010). An assessment of 20 samples collected over a period of time was conducted to determine the amount of nutrients and their variability over time.
Activity 2: Determine nitrogen release rate under different soils
Nitrate release rates of tankage in the dominate soil orders found in the tropics (e.g. Andisol, Mollisol, Ultisol, and Oxisol) was determined in replicated RCB designed greenhouse trials in Hawaii.
Activity 3: Field trials
Experiments were conducted during March to June in year 1 and September to December in year 2 at one farm on the island of Oahu (Poamoho Produce) and one farm in American Samoa (Gurr Farms). Experiments were replicated four times and arranged in a randomized complete block design (RCBD) with three application rates based on addition of nitrogen at 150, 300, and 600 pounds on N per acre. The two control treatments included no application of any inputs and a synthetic fertilizer application to supply 150 pounds per acre N. Crops were harvested at market maturity and evaluated for yield and market grade. A second crop was planted and soil samples taken to estimate residual nitrogen availability. Data analysis conducted as above.
Objective 3 (Year 1-3)
Activity 1: Determining nutrient content of algae species
Three algae species were collected at multiple bays on Oahu, Molokai, and Hawaii islands. The target algae species are Avrainvillea amadelpha (leather mudweed), Acanthrophora spicifera (spiny seaweed), and Gracilaria salicornia (gorilla ogo). Mineral nutrients, heavy metal, and salt content were determined on 10-20 samples of each species from each location using standard procedures. Preliminary studies indicate that washing algae leaches potassium to a greater extent than sodium. A series of washing treatments were applied to algae to determine the impact of washing on nutrient and salt content of the algae.
Activity 2: Nutrient availability
Greenhouse experiments on algae with highest K content were conducted using three different application rates and three grinding sieve sizes. The experimental design was a randomized complete block design (RCBD) with four replicates. Multiple plant species were grown (lettuce, papaya, and taro) to determine the impact of application rate and grinding on nutrient (especially K) uptake. Potassium and other nutrient concentrations in plant tissue were determined using standard procedures by the Agricultural and Diagnostic Service Center (ADSC).
Activity 3: Field trials
Two field trials were conducted with participating growers (Poamoho Produce, Mohala Farms) to evaluate the effect of replacing imported potassium inputs with optimally processed algae. Experiments were replicated four times as described above. Plant growth, K-uptake, and final crop quality were evaluated. Two plant species (papaya and lettuce) were grown. Quality evaluation focused on texture and shelf-life, characteristics significantly affected by K nutrition.
Objective 4. (Year 3-4)
Activity 1: Conduct community outreach
Outreach activities to extend the project results to growers and other specialists included: workshops and field days conducted for interested parties (farmers, growers, scientists, and extension personnel) where study findings were presented and the development of publications and videos which will be extended using the systems such as e-newsletters and websites now in place. Technology transfer efforts focused on the methodologies used in this experiment to determine on-site quality and maturity of composts, and compost effect on growth and yield of crops. Websites to which materials will be posted include: SOAP: http://www.ctahr.hawaii.edu/sustainag/index.html; eXtension: http://www.extension.org/; For additional details regarding dissemination and outreach, please see outreach plan below.
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 indications of compost quality, but other factors such as N release rate should be included.
2) The rate of N mineralization from different composts has a narrow range of 0.02–0.03/day.
3) Composts can (with N content > 2%) provide sufficient nutrient to enhance the growth and yield of pak choi and there is a potential for long-term improvement in soil fertility and quality due to compost applications;
4) Please see publications/outreach section for more details.
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 that the K content in the three algae species were 15-20% from samples collected over two years period;
3) Establish a recommended application rate of 200-250 lbs K/acre from dried algae for high K demand crops such as sweet potato and pak choi crops;
4) MSc student was able to complete her degree using the project resources/materials (used the algae species under sweet potato cro
5) On-going effort to establish K release curves from different algae species under peat moss and different soils;
6) Please see publications/outreach section for more details.
Every thre months (between November 2011 to August 2015), 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% and tankage can be a good source of other nutrients (such as P average 3%);
2) There is a chance of N loss (10-15% annually) of the initial N from tankage during storage; the decline depends on the storage conditions, especially temperature and humidity;
3) In lab leachate studies using tankage applied at different N rates in Mollisol and Oxisol soils, 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;
4) A recommended application rate of 1,500 to 3,000 lbs/acre was established for different crops (i.e. eggplant, taro, corn, pak choi and others), based on the crop demand and growth duration;
5) Please see publications/outreach section for more details.
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).
- Bio-security protocols have reduced concerns of algae spread to other areas.
- There is an increased demand for locally produced tankage, from Island Commodity Co. The increased reliance on the local inputs will reduce demand for off-state fertilizers.
- Farmers utilizing the invasive algae, mainly taro and sweet potato farmers, are reporting increase in the yield and quality of their crops.
- Increased incorporation and utilization of locally produced composts among small-farm holders. This may lead to increase net-benefits, due to reduction in production cost.
Educational & Outreach Activities
Peer-reviewed articles and book chapters:
- Nitrogen release patterns of some locally made composts and their effects on the growth of Chinese cabbage (Brassica rapa, Chinensis group) when used as soil amendments. 2014. Amjad. A. Ahmad, N. V. Hue, and Theodore J.K. Radovich. Compost Science & Utilization 22(4): 199-206.
- Enhancing soil function and plant health with locally available resources. Book Chapter In: Food-Producing Agroforestry Lanscapes of the Pacific (Series). 2014. Radovich, T., A. Pant, A. Ahmad, C. Elevitch, and N. Hue.
- The Effect of Invasive Seaweed (Eucheuma Spp.) and Tankage, as a Soil Amendment, on Sweet Potato Growth in Two Hawaiian Soils. 2014. Jeana Cadby. MSc. Thesis, University of Hawaii at Manoa.
Under review Peer-reviewed articles:
A correlation of rapid Cardy meter sap test and ICP spectrometry of dry tissue for measuring potassium (K+) concentrations in pak choi (Brassica rapa Chinensis group). 2015. Chandrappa Gangaiah, Amjad Ahmad, Hue Nguyen, and Theodore J.K. Radovich. Under review at the Journal of Communications in Soil Science and Plant Analysis.
The effects of invasive algae sp. (Eucheuma Denticulatum& Kappaphycus alvarezii)as sources of potassium (K+) nutrient for yield and leaf nutrient concentration of Pak Choi (Brassica rapa, Chinensis Group). 2015. Chandrappa Gangaiah, Theodore J.K. Radovich, and Amjad Ahmad. To be submitted to HortScience Journal.
Amjad Ahmad, T. J.K. Radovich, N.V. Hue, and L.J. Cox. 2013. Hawaii’s Locally Produced Composts: Nitrogen release and effects on pak choi (Brassica rapa var. chinensis) growth. HanaiAi (Sustainable and Organic Agriculture Program). http://www.ctahr.hawaii.edu/sustainag/news/articles/V14-Ahmad-LocalCompost.pdf.
Amjad Ahmad, A. Fares, T. JK. Radovich, and N.V. Hue. 2012. Using Manures to Improve Sweet Corn Biomass and its Nutrient Content. HanaiAi (Sustainable and Organic Agriculture Program). http://www.ctahr.hawaii.edu/sustainag/news/articles/V10-Ahmad-corn.pdf.
Amjad A. Ahmad, Jensen Uyeda, and Theodore J.K. Radovich. 2015. Local Organic Fertilizers for Better Yields and Fertile Soils. AgPro Workshop. Western-SARE/USDA/CTAHR. Oct. 13-14, Maui College/Cooperative Extension Services, Maui, Hawaii.
Arnoldus Berek, Hue V. Nguyen, and Amjad A. Ahmad. 2015. Biochar and Compost: To Improve Fertility and Plant Growth in Tropical Soils. Western-SARE/USDA/CTAHR. Oct. 13-14, Maui College/Cooperative Extension Services, Maui, Hawaii.
Amjad A. Ahmad. 2015. Locally Available Organic Fertilizers in Hawaii. Guest Speaker for the Organic Crop Production Course (TPSS 20), Oct. 5, University of Hawaii at Manoa, Hawaii.
Chandrappa Gangaiah, Amjad A. Ahmad, Hue V. Nguyen, and Theodore J.K. Radovich. 2015. Use of Invasive Algae as a Potassium (K) Source Affects Growth and K Content in Pak Choi (Brassica rapa cv. Bonsai, Chinensis Group) under Greenhouse Conditions. HortScience 50(9): S330. ASHS Annual Conference, Aug. 4-7. New Orleans, Louisiana.
Amjad A. Ahmad, Theodore J.K. Radovich, Nguyen V. Hue, Alton Arakaki, Glenn Teves, Jari Sugano, and Jensen Uyeda. 2015. Local Sources of Soil Fertility. Western Sustainable Agriculture Research and Education (SARE) Agroforestry Workshop Series. June 12-13 on Maui, and 20-21 on Kona, Hawaii.
Amjad A. Ahmad, Theodore J.K. Radovich, and Nguyen V. Hue. 2015. Local Inputs to Enhance Soil Fertility and Plant Growth in Agroforestry Systems. Western Sustainable Agriculture Research and Education (SARE) Agroforestry Workshop Series. March 21 on Molokai and April 25-26 on Kauai, Hawaii.
Chandrappa Gangaiah, Amjad A. Ahmad, and Theodore J. K. Radovich. 2015. A comparison of rapid Cardy meter sap test and ICP spectrometry of dry tissue for measuring potassium (K+) concentrations in pak choi (Brassica rapa Chinensis group). CTAHR 27th Annual Symposium, Apr. 10-11. University of Hawaii-Manoa, Honolulu, Hawaii.
Amjad A. Ahmad, Theodore J.K. Radovich, and Nguyen V. Hue. 2015. Using Locally-Produced Farm Inputs. Guest Speaker at the Molokai Native Hawaiian Beginning Farmer Program, Jan 29, 2015. Molokai Island, Hawaii.
Jeana Cadby, Theodore Radovich, Robert Paull, Nguyen Hue, and Amjad Ahmad. 2014. The concentration of K from invasive seaweed (Eucheuma spp.) when used as a soil amendment in a Hawaiian Oxisol. 29th International Horticultural Congress (IHC), Aug. 17-22. Brisbane, Australia.
Jeana Cadby, Theodore Radovich, Robert Paull, Nguyen Hue, and Amjad Ahmad. 2014. The concentration of K from invasive seaweed (Eucheuma spp.) when used as a soil amendment in two Hawaiian Soils. CTAHR 26th Annual Symposium, Apr. 11-12. University of Hawaii-Manoa, Honolulu, Hawaii
Ahmad, A., T. Radovich, and N.V. Hue. 2013. Nitrate release dynamics from four organic fertilizers: A lab mineralization study. CTHAR Sustainable Agriculture Workshop Series: Special Focus on Sweet Potato Production. Nov. 5, Aupuni Center, Hilo, Hawaii.
Radovich, T., A. Ahmad, and A. Pant. 2013. Sustainable and Organic Agriculture Laboratory. Sustainable and Organic Agriculture Program’s Extension and Research Update. Sep 25-26, 2013. University of Hawaii-Manoa, Honolulu, Hawaii.
Amjad Ahmad, N. Hue and T. Radovich. 2012. Screening Hawaii’s Locally Produced Composts for Their Nitrogen Release and Plant Growth Response Under Different Soils. HortScience, 47(9): S151-152, ASHS Annual Conference, July 31 to Aug. 3. Miami, Florida.
Ian Gurr, T. Radovich, K. Kobayashi, R. Paull, and A. Ahmad. 2012. Using Hawaii’s Locally Produced Organic Material to Improve Quality of Vegetable Seedlings. HortScience, 47(9): S150, ASHS Annual Conference, July 31 to Aug. 3. Miami, Florida.
Training Opportunities for Farmers and Students:
Chandra Gangaiah, PhD Dissertation. 2013-Present. Using invasive algae (Eucheuma spp.) as a source of potassium nutrient for crop growth in Hawaii: Effects on crop nutrition & yield of vegetable crops.
Tiara Silvasy. 2014-Present. MSc. Thesis. The use of Tankage as a source of nitrogen in organic farming.
Three high school students received training in conducting lab incubation/leachate column experiments. The students competed for Hawaii State Science and Engineering Fair, and two of them went to the International Science and Engineering Fair competition.
- Our recent N analysis confirmed that average N content in tankage is 10%. Farmers used to apply tankage based on 8.5% N content, resulting in over-application. We estimated that farmers can save about $100 per acre from that over-application.
- Replacing potassium application from synthetic K to the invasive algae, especially for crops with high K demand (such as taro and sweet potato crops), is estimated to average $200 per acre savings.
- The analysis did not include the long-term benefits of the organic fertilizers (compost, tankage, and algae) on soil fertility and plant growth. Long-term studies are recommended to conduct such analysis.
- Cost-analysis results were incorporated into the public talks given over the project duration.
Formal surveys of the extent of farmers adoption has yet to be conducted. However, communications with growers and producers of local inputs indicate use has increased substantially over course of the project specifically:
- Island Commodities Co., the producer of tankage, confirmed increase in the number of clients and sale of tankage locally over the last three years. Please note that the company used to send the produced tankage to California for disposal, due to minimum interest and awareness of the product quality/availability in Hawaii.
- From a personal communication with the DLNR SuperSuckers team members. There has been increase demand for the harvested invasive algae for organic agriculture use, especially among the taro and sweet potato growers.
Areas needing additional study
- Due to the increased demand among local famers for more information about the effect of biochar in improving plant growth and the long-term enhancement of soil properties, we recently started to incorporate the locally produced biochar with different organic fertilizers to evaluate its effect on nutrient release and plant growth response, in order to recommend it to the local farmers in Hawaii and the Pacific Islands.
- Due to the continuous release of new organic fertilizers with different nutrient content, there is a need to study the quality and nutrient (mainly N) release pattern and plant growth response.
- In anticipation FSMA, comprehensive analysis for compliance with food safety regulation is recommended.