Enhancing Phytonutrient Content, Yield and Quality of Vegetables with Compost Tea in the Tropics

Final Report for SW07-073

Project Type: Research and Education
Funds awarded in 2007: $162,500.00
Projected End Date: 12/31/2011
Region: Western
State: Hawaii
Principal Investigator:
Dr. Theodore Radovich
University of Hawaii, Manoa
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Project Information

Abstract:

Water-based extracts of compost (compost “tea”) have long been recognized as potentially valuable in promoting plant growth. Recent innovations in production and application have popularized it’s use among food producers, landscape managers and other interested in promoting plant health. This renewed interest in compost tea has made the input fairly controversial, and it is often presented as either a “Silver Bullet”, or conversely, “Snake Oil.” Like most other historically used agricultural inputs, compost tea is neither. Unfortunately, our ability to effectively employ compost teas to their full advantage is severely limited by our poor understanding of the interactions between compost type, crop and environmental factors as they relate to plant yield and quality, particularly under tropical conditions. These gaps in our knowledge limit the efficacy of compost tea applications on the farms that currently employ this strategy, but seriously restrict the extension and adoption of compost tea technology to conventional farms that want to improve the sustainability of their operations.
This project engaged farmers, researchers and industry professionals to address these gaps in our knowledge through a series of on-farm trials and educational activities in a broad range of tropical island environments to achieve the following objectives:
1) Quantify the independent and interactive effects of compost quality extraction method and crop management on yield and phyto-nutrient content of model root, fruit and leaf vegetables.
2) Determine, at the whole-farm level, the effect of compost tea applications on yield, phyto-nutrient content, and profitability with commercial vegetable operations on three islands in Hawai’i.
3) Build and enhance the capacity of at least 300 growers to effectively employ compost tea to increase vegetable yield and phyto-nutrient content on their farms.
In addition to novel scientific research, peer-reviewed publications and extension bulletins, the activities under each of these objectives has provided for the training of hundreds of farmers through on-farm workshops and farmer-to-farmer networking, and the development of a region-specific compost tea manual. As a result of these products, we have documented: 1) Improved understanding of the ecological processes involved with successful management of sustainable agricultural systems, 2) Successful adoption of compost tea technology by workshop participants and other growers engaged in project activities and 3) Increased partnership between researchers, farmers and industry professionals.

Project Objectives:

This project engaged farmers, researchers and industry professionals to address strategic gaps in our knowledge and resource base through a series of on-farm trials and educational activities in a broad range of tropical island environments. These activities to achieve the following objectives:

1) Quantify the independent and interactive effects of compost quality extraction method and crop management on yield and phyto-nutrient content of model root, fruit and leaf vegetables.

2) Determine, at the whole-farm level, the effect of compost tea applications on yield, phyto-nutrient content, and profitability with commercial vegetable operations on three islands in Hawai’i.

3) Build and enhance the capacity of at least 300 growers to effectively employ compost tea to increase vegetable yield and phyto-nutrient content on their farms.

Introduction:

Aqueous extracts of compost (compost tea) possess significant potential to improve crop health (Weltzien, 1991) and, subsequently, yield and nutritional quality. The benefits of compost extracts to plant health are attributed in large part to the ability of compost and their aqueous extracts to confer resistance to biotic stressors (pests), a phenomenon that is well documented (Hoitink, 1997, Zhang et al., 1998). The primary mechanisms of compost-conferred pest resistance include 1) enhanced plant nutrition and 2) an increase in secondary plant metabolites (phyto-nutrients) that is elicited by organic acids, fungi, bacteria and microbial products found in compost (Kuc, 2006). Both of these mechanisms contribute to grower profitability by improving plant yield. In addition, increases in secondary plant metabolites such as glucosinolates, carotenoids and phenolic compounds have important implications to human health, crop flavor, and commodity value because of their demonstrated biological reactivity and association with anti-carcinogenic and organoleptic activity in humans (Radovich et al, 2005a). The ability to consistently elicit high levels of phyto-nutrients with compost tea would allow for the possibility to increase farm profitability by certifying produce as grown under conditions that promote crop flavor and nutritive value (Scientific Certified Systems, 2006).

The potential benefits of compost tea are substantial and are particularly relevant to agricultural production in tropical island environments through their promotion of reduced reliance on off-island inputs, employing natural biological cycles to mitigate year-round pest pressure, environmentally sound waste management to protect watersheds and reefs, and improved profitability of small and mid-sized farms that predominate large farms in these areas.

Compost type is critical to tea quality, which in turn interacts with the unique physiology of each crop and its growing environment (Ingham, 2005). Unfortunately, our ability to effectively employ compost teas to their full advantage is severely limited by our poor understanding of the interactions between compost type, crop physiology and environmental factors as they relate to plant yield and phyto-nutrient content, especially under tropical conditions. These gaps in our knowledge not only limit the efficacy of compost tea applications to optimize crop yield and nutritive quality on the certified organic farms that predominantly employ this strategy currently, but seriously restrict the extension and adoption of compost tea technology to conventional farms that want to improve the sustainability of their operations.

Cooperators

Click linked name(s) to expand
  • Michael Alms
  • Tane Datta
  • Wei Chong Ho
  • Kelly Lange
  • Gerry Ross
  • Stephen Talcott

Research

Materials and methods:

OBJECTIVE 1

Laboratory, greenhouse and field experiments were conducted in order to identify and describe: 1) the effects of vermicompost tea extraction methods [(i) non-aerated (NCT), (ii) aerated (ACT), and (iii) aerated with additives (ACTME)], 2 fertilizers (Osmocote and vermicompost), and three growth media (Oxisol, Mollisol and a peat-perlite medium) on yield and nutritional quality of pak choi (Brassica rapa, Chinensis) as well as soil biological properties; 2) the effects of the ratio of vermicompost to water and different fertilizers on yield and nutritional quality of pak choi as well as soil biological properties; 3) the effect of compost quality on biochemical properties of compost tea; and 4) mechanisms involved in the effects of compost tea on plant growth. For a full description of methodologies used, please see the attached dissertation (Pant_2011).

OBJECTIVE 2.

Three commercial growers were selected for on farm trials. The first two growers were early adoptors that had been using compost tea with about 15 years of collective experience. Replicated trials were established on their farms to evaluate the imapct of removing tea from their production system using pak choi and potatoes as model crops. Yield and nutrient data were collected at harvest and statistically analyzed as per standard practices. The third farm selected was a conventional farm interested in reducing their waste stream. They developed a static pile composting system to recycle their culled vegetables. This compost was then used in a replicated field trial at the University of Hawaii Waimanalo Experiment Station using a brewer designed from local materials. This study was designed
specifically to evaluate a system of tea production and application that was both feasible for growers and in agreement with our current
understanding of the optimal rates of compost tea for improving plant growth as derived from results in Objective 1. Growers were involved with the planning and management of trial activitiess. See the attached Compost Tea Manual, pages 16-18 and 35-39 for more details.

Objective 3.
A series of publications, presentations and web-based resources were developed to improve the basic understanding of growers, agricultural professionals, researchers and other stakeholders regarding the potential benefits and limitations of compost tea. See Milestones below for more details.

Research results and discussion:

The result showed that applications of vermicompost tea, regardless of extraction method, increased plant yield, mineral nutrients, phytonutrient content of pak choi; and microbial activities of an Oxisol, a Mollisol or a peat-perlite medium and this effect was most prominent under organic fertilization. This finding suggests that vermicompost tea serves both as a supplemental source of plant nutrients and an enhancer of soil biological properties. Similarly, application of vermicompost tea with vermicompost to water ratios of 1:10 – 1:100 (v:v) increased yield, total carotenoids, total glucosinolates and N content of pak choi; and microbial activities in soil. The responses of these parameters to vermicompost to water ratio was positive and linear. The results also indicated that biochemical properties of compost determined biochemical properties of compost tea, and the resulting quality of tea positively impacted plant growth and tissue mineral nutrient. The positive influence of vermicompost tea or compost tea on plant growth was largely associated with N and gibberellin4 (GA4) present in the tea and nutrient uptake by plants. Overall, results from these studies improve the understanding of vermicompost tea effects on yield and nutritive quality of pak choi as well as soil biological properties. Dee attached Dissertation for more details (Pant_11).

OBJECTIVE 2.

The on-farm trials with early adoptors suggested that compost tea had negligible short term contributions to these systems in during the time of the study. Several reasons are suggested for this, including: 1) inadequate quantities of compost used for brewing, and 2) long time use of compost tea and other amendments has established an “equilibrium” on the farm. The third trial, tea applications resulted in subtle, but significant increases in dry matter production in pakchoi heads after 5 weeks. On a fresh weight basis, heads in plots receiving tea were 14% heavier than heads not receiving tea. Assuming a planting density of 29,000 plants per acre, yields in this trial are extrapolated to be 7.7 and 6.6 tons per acre for tea and no tea plots, respectively. Assuming a wholesale price of $1.50 per pound, this translates to a potential increase in farm-gate value of $3,300 per acre in the tea plots. Although it is not possibleto determine the exact costs of the on-farm produced compost, it is estimated at $50 a yard (1 cubic yard = 202 gallons of compost). If 300 gallons of tea are applied 4 times during the crop cycle, this is equivalent to 10 gallons of compost at a 100:1 ratio, or $3.00 of compost for the whole crop. Even if the highest prices for vermicompost are used ($3/pound or $57 per acre), the cost benefit appears to be favorable. See the attached Compost Tea Manual, pages 16-18 and 35-39 for more details.

Objective 3.

See Publications/Outreach activities below

Research conclusions:

In addition to novel scientific research, peer-reviewed publications and extension bulletins, the activities under each of these objectives has provided for the training of hundreds of farmers through on-farm workshops and farmer-to-farmer networking, and the development of a region-specific compost tea manual. As a result of these products, we have documented: 1) Improved understanding of the ecological processes involved with successful management of sustainable agricultural systems, 2) Successful adoption of compost tea technology by workshop participants and other growers engaged in project activities and 3) Increased partnership between researchers, farmers and industry professionals.

Participation Summary

Educational & Outreach Activities

Participation Summary

Education/outreach description:

The following Publications and presentation have be produced as outputs of this project:

PEER REVIEWED ARTICLES

Pant, A., T.J.K. Radovich, N.V. Hue, N. Arancon. 2011. Effects of Vermicompost Tea (Aqueous Extract) on Pak-choi Yield, Quality, and Soil Biological Properties. Compost Science and Utilization (In Press).

Pant, A., T.J.K. Radovich, N.V. Hue, S. T. Talcott, and K.A. Krenek. 2009. Compost extracts influence growth, total carotenoids, phenolics and antioxidant activity in Pak choi (Brassica rapa Chinensis group) grown under two fertilizer regimes. Journal of the Science of Food and Agriculture 89:2383-2392.(see 2009 report)

B. Sipes, G. Taniguchi, and T. Radovich. 2010. Aqueous extract of vermicompost and Actigard effects on pineapple heart rot. Acta Horticulturae (in press).

EXTENSION PUBLICATIONS

T. Radovich and N. Arancon (eds.). 2011. Tea Time in the Tropics. Compost Tea Manual. (See attched)

T. Radovich. 2011. Promoting plant growth with compost teas. Hana’Ai Sustainable and Organic Agriculture Program newsletter. University of Hawaii, College of Tropical Agriculture and Human Resources. September, 2011. (attached)

T. Radovich. 2009. Vermicompost Research Update 2009. Hana’Ai Sustainable and Organic Agriculture Program newsletter. University of Hawaii, College of Tropical Agriculture and Human Resources. September, 2009.

WORKSHOPS

Compost Mana’o (mana’o = wisdom). February 5, 2011. Kupa’a Farms. Kula, Maui. 90 attendees

Compost Tea Workshop. Molokai New Farmer Program. Hoolehua, Molokai. 15 attendees.

Compost and Compost Tea Workshop. May 6, 2011. Hilo, Hawaii. 100 Attendees.

EXTENSION PRESENTATIONS

Promoting plant growth with aqueous extracts of compost. CTAHR Research Update. Honolulu 4/26/2010. 55 attendees.

Promoting plant growth with aqueous extracts of compost. Integrated Crop and Livestock Management Workshop. Hilo. 6/06/2010. 55 attendees.

SCIENTIFIC PRESENTATIONS

Pant, A., T.J.K. Radovich, N.V. Hue. 2010. Application of Vermicompost Extract On Pak-Choi: Effects On Yield, Quality, and Soil Biological Properties. Annual Meeting of the American Society for Horticultural Science, Desert Palms, CA.

Pant, A., T.J.K. Radovich, N.V. Hue and J.P. Bingham. 2010. The Influence of Compost Origin On Chemical and Biological Properties of Compost Extracts and Pak Choi (Brassica rapa Chinensis Group) Yield. Annual Meeting of the American Society for Horticultural Science, Desert Palms, CA.

Pant, A., T.J.K. Radovich and N.V.Hue. 2009. Vermicompost Extracts Influence Growth, Total Carotenoids, Phenolics and Antioxidant Activity in Pak Choi (Brassica rapa cv. Bonsai, Chinensis group) Grown Under Vermicompost and Chemical Fertilizer. Annual Meeting of the American Society for Horticultural Science, St. Louis MO.

Project Outcomes

Project outcomes:

Simple economic analysis were conducted as part of activities under Objectives 1 and 2, using pak choi as the model crop. If produced and applied as recommended it is estimated that net gains in farm gate value of $2,000-$4,000 per acre may be achieved, using pak choi as a model crop. See page 176 of Dissertation (Pant_11) and page 39 of Compost Tea Manual for details.

Farmer Adoption

Farmers continue to adopt compost tea in Hawaii. Examples of farmers who have adopted compost tea since the initiation of this project are given on pages 26, 40 and 55 of the attached Compost Tea Manual.

Recommendations:

Areas needing additional study

Our work has clearly identified the byproducts of microbial activity (e.g. nitrate and gibberellic acid), rather than microbial activity, as the primary mechanisms for promoting plant growth in this project.
Priority is now being placed on elucidating the role of microorganisms in the composting process as it impacts the efficacy of compost teas.

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.