Amendment of a hardwood biochar with compost tea

Biological Agriculture & Horticulture An International Journal for Sustainable Production Systems

ISSN: 0144-8765 (Print) 2165-0616 (Online) Journal homepage: http://www.tandfonline.com/loi/tbah20

Amendment of a hardwood biochar with compost tea: effects on plant growth, insect damage and the functional diversity of soil microbial communities Sherie L. Edenborn, Linda M. K. Johnson, Harry M. Edenborn, Mirna R. Albarran-Jack & Laura D. Demetrion To cite this article: Sherie L. Edenborn, Linda M. K. Johnson, Harry M. Edenborn, Mirna R. Albarran-Jack & Laura D. Demetrion (2017): Amendment of a hardwood biochar with compost tea: effects on plant growth, insect damage and the functional diversity of soil microbial communities, Biological Agriculture & Horticulture, DOI: 10.1080/01448765.2017.1388847 To link to this article: http://dx.doi.org/10.1080/01448765.2017.1388847

View supplementary material

Published online: 24 Oct 2017.

Submit your article to this journal

Article views: 38

View related articles

View Crossmark data

Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=tbah20 Download by: [73.117.22.237]

Date: 04 November 2017, At: 09:15

BIOLOGICAL AGRICULTURE & HORTICULTURE, 2017 https://doi.org/10.1080/01448765.2017.1388847

Amendment of a hardwood biochar with compost tea: effects on plant growth, insect damage and the functional diversity of soil microbial communities Sherie L. Edenborna, Linda M. K. Johnsona, Harry M. Edenbornb, Mirna R. Albarran-Jackc and Laura D. Demetriond Department of Biology, Chatham University, Pittsburgh, PA, USA; bNational Energy Technology Laboratory, U.S. Department of Energy, Pittsburgh, PA, USA; cGlenn County Department of Agriculture, Willows, CA, USA; dBooz Allen Hamilton, Washington, DC, USA

Downloaded by [73.117.22.237] at 09:15 04 November 2017

a

ABSTRACT

Biochar is an organic soil amendment that has been shown to improve plant growth and increase resistance to plant diseases and insect damage in certain soils. Organic growers have been known to use compost teas to amend biochar, claiming that this practice adds nutrients and beneficial microorganisms that can improve plant growth and resistance to pathogens and insect pests. However, few data exist to support this hypothesis. This study investigated the effects of a hardwood biochar amended with different types of compost teas and microbial enrichments (prepared from vermicompost) on eggplant (Solanum melongena var. Rosa Bianca) growth, flea beetle (Epitrix fuscula) damage, and soil microbial activity and functional diversity in two temperate soils. No positive short-term effects were observed on eggplant growth or flea beetle damage when biochar amended with compost teas prepared from horse manure, mushroom compost or vermicompost were added to a temperate agricultural soil. However, a second experiment suggested that biochar amended with microbial enrichments from vermicompost tea may improve eggplant growth if matched with the physical and chemical properties of a given soils. Results from Community Level Physiological Profiling (CLPP) revealed that biochar amended with compost teas altered soil microbial activity and functional diversity differently to that of biochar alone, and that these changes corresponded with plant growth and insect damage.

ARTICLE HISTORY

Received 2 November 2016 Accepted 3 October 2017 KEYWORDS

Biochar amendment; compost tea; vermicompost; microbial inoculants; functional diversity; microbial activity

Introduction Soil amendments such as compost and manure have traditionally been used in organic food production systems to enhance and maintain long-term soil fertility and suppress insect pests and microbial pathogens (Altieri and Nicholls 2003). Recently, biochar, a carbon-rich, charred organic matter that is produced through the pyrolysis of biomass, has been evaluated as another soil amendment (Lehmann and Joseph 2009; Sohi et al. 2010; Kookana et al. 2011; Spokas et al. 2012). Some studies suggested

CONTACT Sherie L. Edenborn [email protected] Supplemental data for this article can be accessed at https://doi.org/10.1080/01448765.2017.1388847. © 2017 Informa UK Limited, trading as Taylor & Francis Group


2

S. L. EDENBORN ET AL.

that biochar can increase plant growth in specific soils by modifying soil characteristics such as moisture holding capacity, cation exchange capacity (CEC) and pH, as well as improving plant nutrient availability and seed germination rate (Jones et al. 2012; Spokas et al. 2012; Schulz et al. 2013). Other evidence suggested that biochar may also induce systemic disease resistance against fungal pathogens and insect herbivores (Elad et al. 2010; Graber et al. 2010; Harel et al. 2012). The widespread production and use of biochar as a soil amendment could also ultimately lessen greenhouse gas emissions to the atmosphere due to its slower rate of biomineralisation in soil compared to fresh organic matter (Lehmann and Joseph 2009; Spokas et al. 2012). In contrast, biochar amendments have also been found to occasionally lower soil fertility and decrease plant growth (Spokas et al. 2012), deplete native soil organic matter (Wardle et al. 2008), reduce the effectiveness of herbicides (Jones et al. 2011) or slow the degradation of soil pollutants (Rhodes et al. 2008). The observed variable effects of biochar on soil quality and plant productivity are, in part, a function of the combined effects of both soil and biochar types. Biochars generated using different production methods and originating from different types of biomass resulted in material with distinctive chemical and physical properties that had correspondingly variable effects on soil chemistry and biology (Spokas et al. 2012; Novak and Busscher 2013; Novak et al. 2013). The often unpredictable effects might be mitigated by creating ‘designer biochars’ that are well-characterised and more suitable for different soil types and specific agricultural and environmental applications (Novak and Busscher 2013; Novak et al. 2013). Designer biochars are typically crafted by varying the types of biomass, as well as the conditions that are used during pyrolysis (Novak and Busscher 2013). Further biochar modifications, such as the addition of beneficial microorganisms or nutrients, have been suggested (Thies and Rillig 2009; Lehmann et al. 2011). The addition of nutrients or microorganisms to biochar prior to its introduction to soil is often referred to as ‘charging’ or ‘activating’ the biochar, although it remains unclear whether sites on the biochar are specifically modified by the added nutrients and/or microorganisms from compost teas. Without evidence to the contrary, compost tea can only be considered an amendment. However, biochars that have been amended with inorganic fertilisers (Alburquerque et al. 2013) and compost (Fischer and Glaser 2012) have been shown to capture nutrients such as nitrate, phosphorous and dissolved organic carbon (DOC) that are slowly released into soil to improve plant growth and root migration (Prost et al. 2013; Prendergast-Miller et al. 2014; Kammann et al. 2015). Nutrient-loading has also been observed to lessen the reduction in plant growth that otherwise can occur when freshly-produced biochar adsorbs or entraps existing nutrients in soil, such as ammonia and nitrate (Ding et al. 2010; Taghizadeh-Toosi et al. 2012; Ippolito et al. 2015). Compost tea is a liquid solution produced by fermenting the filtered components of compost in water that is either aerated (ACT) or non-aerated (NCT) (Ingham 2000). Compost teas, like biochars, have been observed to increase plant growth and disease resistance and are very heterogeneous due to differences in the waste materials that are used to produce the parent compost as well as differences in production and application methods (Scheuerell and Mahaffee 2002; St. Martin & Brathwaite 2012). Compost teas are typically applied via foliar spray or soil drench (Ingham 2000). An advantage of applying compost tea and compost tea-amended biochar to the root zone is that some biochars have been found to enhance the growth of beneficial microorganisms, such as plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) (Graber et al. 2010), which are primarily found in the rhizosphere (Pieterse et al. 2014) and thought to be associated with the ability of compost teas to suppress plant disease (St. Martin & Brathwaite 2012). In practice, organic growers are known to have used compost teas to amend biochar, claiming that this practice adds nutrients and beneficial microorganisms and is more consistent with the principles of sustainable agriculture than the use of inorganic fertiliser amendments (Bates 2010). A patent has recently been issued for a method to ‘bioactivate’ biochar with materials such as compost tea (Cheiky and Sills 2013). However, the effectiveness of this practice on plant growth, disease resistance and soil microorganisms has not been fully tested experimentally.

BIOLOGICAL AGRICULTURE & HORTICULTURE

3

The purpose of this study was to evaluate the effects of a single hardwood biochar that had been amended with different compost teas or microbial enrichments on the growth of eggplant (Solanum melongena var. Rosa Bianca), flea beetle (Epitrix fuscula) damage, and the activity and functional diversity of soil microbial communities, in two different temperate soils.


Materials and methods Two studies were done to evaluate the effects of biochar + compost teas and biochar + microbial enrichments from compost teas on the growth of eggplant (S. melongena cv. Rosa Bianca), on damage by the eggplant flea beetle (E. fuscula), and on soil microbial activity and functional diversity. Three freshly-brewed teas prepared from a vermicompost (VC1), a mushroom compost (MC) and a horse manure compost (HMC) as well as two commercially-prepared teas (CT1 and CT2) were used in Experiment 1. Experiment 2 compared the effects of biochar + compost teas and biochar + microbial enrichments (prepared from three vermicompost teas) on plant growth and the corresponding soil microbial responses. Characterisation and processing of soil, biochar, compost and compost teas Soil samples used in experiment 1 (Soil 1) were collected from an organic garden at Chatham University’s Eden Hall Campus in Gibsonia, PA, U.S.A. and had a near-neutral pH (Table 1), moderate levels of organic matter and micronutrients, and low-to-medium concentrations of N, P and K (Table 2). Soils in this area are Hazleton loam: loamy-skeletal, siliceous, active, mesic, Typic Dystrudrepts. Soil used in experiment 2 (Soil 2) was collected from an urban garden in Pittsburgh, PA, U.S.A. and had a slightly lower pH (6.2), no detectable nitrate or ammonia, lower % organic matter and more P (Table 2). Soils in this area are 75% human-transported soils, 20% Rainsboro silt loam, and 5% other soils. Soil samples were randomly collected from the top 0.3 m and immediately transported back to the laboratory, where they were bulked, mixed, and sieved (