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5-20-2012 Effects of Vermicompost in Potting Soils and Extract Foliar Sprays on Vegetable Health and Productivity Anna Rose Farb Dickinson College

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Recommended Citation Farb, Anna Rose, "Effects of Vermicompost in Potting Soils and Extract Foliar Sprays on Vegetable Health and Productivity" (2012). Dickinson College Honors Theses. Paper 27.

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Effects of vermicompost in potting soils and extract foliar sprays on vegetable health and productivity

By

Anna R. Farb

Submitted in partial fulfillment of Honors Requirements for the Department of Environmental Science

Dr. John H. Henson, Supervisor Dr. Thomas R. Raffel, Reader Dr. Gregory J. Howard, Reader Dr. Michael D. Beevers, Reader

May 14, 2012 Abstract

According to previous studies, vermicompost has been found to promote beneficial organisms, nutrient life, transplant growth and disease suppression in potting soils and aqueous extracts. The objective of our study was to test whether food waste-based vermicompost and thermophilic compost produced at Dickinson College Farm, Boiling

Springs, PA, would improve productivity when applied to agricultural plants via potting media and extract foliar sprays. Romaine lettuce (Lactuca sativa L. var. longifolia) and pak choi (Brassica rapa var. chinensis) seeds were planted with vermicompost-amended, thermophilic compost-amended, unamended, or McEnroe commercial potting media.

Compost-amended media contained greater nutrient contents than unamended media.

Vermicompost-amended media at 10% had significant negative effects on germination compared to the unamended controls (P<0.001), likely due to ammonium toxicity. However, transplant growth was significantly greater in 10% vermicompost-amended potting media

(P<0.001 for all parameters). Among all assessed on-farm media, optimal transplant growth was achieved with 20%-30% vermicompost and the blood meal mix nutrient amendment.

Extracts did not significantly impact transplant growth. The efficacy of vermicompost preparations likely depended on its particular nutrient and microbial content, which can vary from batch to batch. Farm-based vermicompost systems show potential for improving plant productivity and health depending on management and application methods; thus, farms, especially those committed to sustainable, agroecological practices, could benefit from developing on-farm vermicompost systems. However, care should be taken to avoid use of vermicompost batches with high ammonia levels, which can result if compost is removed from the system before reaching maturity.

1 Table of Contents Introduction 3 Objectives 11 Materials and Methods 12 Experiment 1 16 Experiment 2 19 Experiment 3 22 Results and Discussion 25 Experiment 1 26 Experiment 2 33 Experiment 3 39 Discussion 46 Conclusions 50 Acknowledgements 51 References 52

2 Introduction

Organic agriculture has utilized the composting process not only to process on-farm waste, but also to apply the product to fields for soil enrichment. Vermicompost involves the use of surface dwelling worms, Eisenia fetida, or “red wigglers,” in addition to microorganism activity, to convert organic materials into rich humus through their digestive processes (Figure 1). The vermicomposting process occurs at ambient temperatures, differentiating it from traditional thermophilic compost systems, as shown in Figure 2 (Jack

& Thies, 2006). Compared to thermophilic compost, vermicompost can contain significantly higher levels of available nutrients and larger and more diverse microbial communities

(Atiyeh et al., 2000c; Tognetti et al., 2007; Edwards, 1998).

Figure 1. Worms feeding on food waste in Dickinson College Farm’s vermicompost bed.

3

Figure 2. Temperature curve for vermicompost and thermophilic compost over time, the arrows depicting the main phases of the composting process. The thin gray line indicates vermicompost temperatures, and the black dotted line represents thermophilic compost temperatures (Jack & Thies, 2006). The product of the vermicomposting process is a finely divided soil-like material with high porosity, aeration, drainage, and water retention. The worms ingest pathogenic bacteria and fungi, and interactions between worms and microorganisms stabilize the material

(Edwards & Burrows, 1988). Red wigglers process raw or partially decomposed organic waste very efficiently; they can consume their body weight in feedstock on a daily basis.

After the food is ground up by ingested stones in the worm’s gizzard, it passes through the intestinal tract, in which digestive enzymes are secreted that concentrate nutrients

(Dickerson, 2001). Moreover, the large surface areas of worm castings provide increased space for microbial activity and strong nutrient retention (Shi-wei & Fu-zhen, 1991). Thus, vermicompost supports diverse populations of microorganisms and is rich in nutrients

(Edwards & Burrows, 1988). Nutrients contained in vermicompost include nitrate, exchangeable phosphorus, soluble potassium, calcium and magnesium, and sulfur, iron, manganese, zinc, copper, and boron, which are readily absorbed by plants (Edwards &

4 Burrows, 1988; Orozco et al., 1996; Theunissen et al., 2010). Vermicomposting cow manure was found to enhance nitrogen mineralization processes and augment conversion rates of ammonium-nitrogen into nitrate (Atiyeh et al. 2000a). Furthermore, castings contain 5-11 times the amount of available nitrogen and phosphorus, 7 times the amount of available potash and 1.5 times the amount of calcium present in normal topsoil (Colliver, 1992;

Dickerson, 2001).

With respect to microbial activity of vermicompost, the high humic substance content supports microorganisms known to foster plant growth and disease suppression, such as bacteria (Bacillus) and fungi (Trichoderma, Sporobolomyces, and Cryptococcus)

(Nagavallemma et al., 2004). Specifically, plant growth-promoting rhizobacteria (PGPR) provide these plant growth and health services by colonizing plant roots aggressively (Jack &

Thies, 2006). When cattle manure-, food-, and paper-based vermicomposts were applied in field-based trials, each type reduced populations of plant-parasitic nematodes significantly and increased populations of fungivorous and bacterivorous nematodes (Arancon et al.,

2003). Beneficial microorganisms within vermicomposts produced from various feedstocks have been found to suppress plant diseases such as Pythium (damping off), Rhizoctonia (root rot), Plectosporium (blight) and Verticillium (wilt); plant parasitic nematodes such as soybean cyst nematodes and root knot nematodes; and arthropod pests, such as cabbage white caterpillars, cucumber beetles, tomato hornworms, mealy bugs, spider mites and aphids

(Arancon et al., 2007). Jack and Nelson (2008) identified the process by which vermicompost suppresses pathogens like Pythium: first, with the presence of vermicompost in soils, fewer vesicles develop, reducing the formation of pathogenic zoospores; and second, the very few healthy zoospores that do form fail to make contact with the plant due to the alteration of

5 chemical cues by vermicompost seed-colonizing microbes. This effectively creates a gradient surrounding the seed through which zoospores cannot pass (Jack & Nelson, 2008).

Therefore, the potential benefits of vermicompost are significant, especially in organic or sustainable agricultural systems.

In order to reap these benefits, vermicompost can be applied directly to plants or dissolved into aqueous extracts for foliar application. Although these methodologies are historically well-established in agricultural systems of Latin America and South Asia, they have only recently proliferated in North American organic farming practices. In Cuba, the shift from industrial agriculture to local and organic agriculture following the collapse of the

Soviet Union in the early 1990s brought about the establishment of large-scale vermicompost centers (Koont, 2011). Based on scholarly scientific research for crop yield maximization within agroecological systems, Cuban organic agriculturalists produce potting soils comprising about 50% vermicompost, 25% thermophilic compost and 25% rice hulls.

Additionally, they amend their raised beds with vermicompost at 10 kg/m2 (Miguel Salcines, personal communication, March 13, 2012; Koont, 2011). Vermicompost applications are much less standardized in the United States, but we can learn from experiences and management techniques from abroad.

The high porosity, aeration, drainage, water retention, nutrients, and beneficial microorganisms of vermicompost make it an excellent component in horticultural potting media and extract foliar sprays. Both forms can enhance plant growth and suppress plant disease (Edwards & Burrows, 1988; Buckerfield et al., 1999; Arancon et al., 2007; Singh et al., 2003). The direct application of vermicompost in its solid form supplies macro- and micronutrients to the soil for plant growth enhancement (Harris et al., 1990). The nutrient

6 content of vermicompost is released slowly, and vermicompost can hold twice its weight in water, which indicates a long nutrient life and high water retention capacity in vermicompost-amended potting media (Colliver, 1992). The amendment of up to 20% pig manure-based vermicompost in potting media significantly enhanced shoot and root weights, leaf areas and shoot:root ratios of tomato and marigold transplants compared to the control media (Bachman & Metzger, 2008). Additionally, the amendment of 10% or 20% food waste-based vermicompost significantly enhanced growth of tomato and marigold transplants, provided all the required nutrients were supplied (Atiyeh et al., 2000c). With respect to vermicompost disease suppression in potting media, amendments of food waste- based vermicompost decreased the severity of Pythium, increased amendments of cow manure-based vermicompost correlated with the suppression of Rhizoctonia and 5 t/ha of paper-based vermicompost or 10 t/ha of food waste-based vermicompost significantly reduced Verticillium incidence (Chaoui et al., 2002). Vermicompost nutrient richness and microbial diversity both contribute to its success as a potting media amendment.

Microbial activity and nutrients can also be transferred from solid to aqueous forms of vermicompost. These aqueous extracts are defined as a “brewed” solution of about 1:1000 compost:water (Carpenter-Boggs, 2005). They can be produced with or without aeration, or with or without nutrient and microbial additives, such as molasses, algal powders and yeast extracts (Arancon et al., 2007). When aqueous vermicompost extracts (also called vermicompost “teas,” which usually include other additives) are applied as foliar sprays, they have been found to improve plant health, yield and nutritive quality by augmenting communities of beneficial microorganisms in soils and plants, enhancing the nutrient content of plants and stimulating the production of compounds that enhance plant defenses (Pant et

7 al., 2009; Scheuerell & Mahaffee, 2002; Carpenter-Boggs, 2005). However, their efficacy is inconsistent, varying by method of extraction, method of application and vermicompost feedstock (Jack, 2010; Atiyeh et al., 2000c; Jack et al., 2011).

Dickinson College Farm (DCF), an Organic and Food Alliance Certified vegetable and livestock farm located in Boiling Springs, PA (Figure 3), recently developed a food waste-based vermicompost program involving both potting media and aqueous extract foliar applications. DCF has a strong commitment to sustainability through responsible stewardship to the land. Ecosystem services provided by compost microbial communities, such as disease suppression and plant growth, which DCF already takes advantage of, help in agroecological management systems to avoid chemical fertilizers and pesticides (Jack et al., 2011).

Thermophilic compost has been produced and used since the foundation of the farm for field soil enrichment. Additionally, DCF grows all its own transplants from seed in the greenhouse, historically using commercial organic potting media. Thus, the farm’s interest in vermicompost applications is based on advancing the utilization of these ecosystem services and extending the localized waste-to-produce closed-loop cycle to transplant substrates through the production of on-farm potting media and extract foliar sprays. Figures 4 and 5 depict preliminary microbial characterizations of the aerated vermicompost extract produced without additives at DCF, which were completed prior to this study (Sinchi et al., 2011).

They show that the on-farm vermicompost in aqueous extract form contains a diverse array of bacteria and fungi.

8

Figure 3. The location of Dickinson College Farm within Cumberland County, PA (Projection: State Plane PA South, Datum: North American Datum 1983, Source: ESRI).

Figure 4. Swab samples from the vermicompost extract were streaked on agar Petri plates. Plates A and B contain mostly bacterial colonies, while Plate C contains both bacterial and fungal colonies (Sinchi et al., 2011).

9

Figure 5. A smooth, rounded bacterial colony (left) compared to a filamentous fungal colony (right) from the vermicompost extract grown on a PDA plate (Sinchi et al., 2011). In addition to investigating the benefits of vermicompost use, we tested for interactive effects of compost type and the type of potting soil base. Due to DCF’s commitment to environmental sustainability, the use of peat moss, the most commonly used soilless medium, is not ideal (Kuepper & Everett, 2010). Emissions from Canadian peat extraction totaled 0.54 x 106 t of greenhouse gases (GHG) in 1990, which increased to 0.89 x 106 in 2000. Most

(about 70%) of these emissions were from peat decomposition associated with end use; however, about 30% came from land use change, transportation and extraction and processing. Furthermore, peatlands switched from being a GHG sink to a source, and it would take 2000 years to restore the carbon pool with effective peatland restoration (Cleary et al., 2005). Coir, a byproduct of the shredding of coconut husks following extraction of their coarse fibers, has been found to be an effective substitute for peat (Handreck, 1993;

Kuepper & Everett, 2010). Coir is a byproduct of coconut production in India, Sri Lanka, the

Philippines, Indonesia, and Central America, and its extraction process is considered more

10 sustainable than that of peat (Nelson, 1998; Handreck, 1993). Growth of tomato, pepper, lettuce, and marigold transplants in coir-based media has been found to be comparable to that of peat-based media, and amending both peat/perlite and coir/perlite media with vermicompost can enhance seedling growth significantly (Atiyeh et al., 2000b). Our study further assessed relationships among coir, peat, and vermicompost.

In most previous studies, vermicompost was provided by large-scale commercial vermicompost production companies. Although this helps ensure that the vermicompost being used is of consistently good quality, it is not representative of vermicompost produced in most practical farm-based management systems fed by on-farm or local organic waste, which is the form that most small-scale sustainably managed farms likely use in practice.

Thus, our study assessed the applications of vermicompost produced on a working small- scale sustainable and organic farm.

Objectives

We aimed to test how the application of on-farm food waste-based vermicompost and thermophilic compost in potting soils and aqueous extract foliar sprays affects vegetable transplant growth through greenhouse-based experiments, relative to commercial potting soil.

Furthermore, we sought to identify the most productive and sustainable on-farm potting mixtures in terms of transplant growth, taking into account effective quantities and environmental renewability of ingredients, so that the farm may supplement its potting soil needs. The ultimate goal was to determine the best way to integrate vermicompost into the frameworks of environmental sustainability and agroecology on DCF.

11 Materials and Methods

Experiments took place on Dickinson College Farm (DCF) during 2011-2012.

Vermicompost was produced using red wiggler worms (Eisenia fetida) and mesophilic microorganisms to decompose organic waste in a large plywood bin with a grated floor, and thermophilic compost was generated by the decomposition processes of mesophilic and thermophilic microorganisms in large windrows (Figures 6 and 7). The thermophilic compost feedstock was composed of food waste from the college’s dining hall, whereas the vermicompost feedstock was composed of vegetable waste from the fields. DCF’s thermophilic compost required 12 months to become mature as was determined by its temperature, and vermicompost took 1-2 months. The worms dwelled at the surface of the bin, where they were fed, and their castings continued down through the system, continuing to be processed by microorganisms. Vermicompost was considered mature when it reached the bottom of the bin and fell through the grated floor onto the collection area.

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Figure 6. Vermicompost (Panel A) and thermophilic compost (Panel B) produced on-site at DCF.

Figure 7. Panel A shows the vermicompost bin, and Panel B shows the thermophilic compost windrow. Samples of on-farm vermicompost and thermophilic compost were subject to physico-chemical analysis by Agricultural Analytical Services Laboratory (AASL) at Penn

State University (pH, soluble salts, solids, moisture, organic matter, total nitrogen, organic nitrogen, ammonium nitrogen, carbon, carbon:nitrogen ration, phosphorus, potassium, calcium, magnesium, sulfur, sodium, aluminum, iron, manganese, copper and zinc). Samples

13 of their respective feedstocks were also subject to physico-chemical analysis by AASL (pH, soluble salts, solids, moisture, organic matter, total nitrogen, carbon and carbon:nitrogen ratio). For the production of the potting media produced on-farm, vermicompost and thermophilic compost were extracted in temporally defined batches. Due to resource and time constraints, we did not control for physico-chemical variability between the batches and spatially within each batch.

The methodologies are presented by experiment following the summary tables and figures, which demonstrate the methodological linkages among experiments. An overall summary of the experiments, including media treatments used, is provided in Table 1.

Vegetables seeded and data collected in each experiment are described in Table 2.

14 Table 1. Media treatment group names and details for each experiment.

Media Details Aqueous extract treatments spray treatments Experiment 1 1/3 VC Equal parts v/v* VC,* vermiculite, peat moss VC 1/3 TC Equal parts v/v TC*, vermiculite, peat moss TC McEnroe Compost, peat moss, sand, rock phosphates, Control (water) calcinated clay, gypsum, blood meal Experiment 2 Base, 10% VC Peat base (70 peat moss: 30 vermiculite v/v, lime (3 - lbs. yd-3 or 1.78 kg m-3), 10% v/v VC Base, 20% VC Peat base, 20% v/v VC - Base, 30% VC Peat base, 30% v/v VC - BM, 10% VC Peat base, 10% v/v VC, BM* mix (blood meal, - greensand, bone char) (7 lbs. yd-3 or 4.15 kg m-3) BM, 20% VC Peat base, 20% v/v VC, BM mix (7 lbs. yd-3) - BM, 30% VC Peat base, 30% v/v VC, BM mix (7 lbs. yd-3) - Base, 10% TC Peat base, 10% v/v TC - Base, 20% TC Peat base, 20% v/v TC - Base, 30% TC Peat base, 30% v/v TC - BM, 10% TC Peat base, 10% v/v TC, BM mix (7 lbs. yd-3) - BM, 20% TC Peat base, 20% v/v TC, BM mix (7 lbs. yd-3) - BM, 30% TC Peat base, 30% v/v TC, BM mix (7 lbs. yd-3) - McEnroe Compost, peat moss, sand, rock phosphates, - calcinated clay, gypsum, blood meal Experiment 3 Peat Peat base, BM mix (7 lbs. yd-3) Control (none), VC Peat, VC Peat base, 10% v/v VC, BM mix (7 lbs. yd-3) Control (none), VC Coir Coir base (70 coir: 30 vermiculite v/v, lime (3 lbs. Control (none), VC yd-3)), BM mix (7 lbs./ yd3) Coir, VC Coir base, 10% v/v VC, BM mix (7 lbs. yd-3) Control (none), VC v/v=volume/volume, VC=vermicompost, TC=thermophilic compost, BM=blood meal

Table 2. Seeds planted, data collected and dates from each experiment.

Experiment Vegetables seeded Data collected Dates 1 Romaine trial 1: 48 per Potting soil analysis, germination (all trials), Sept.-Dec., media treatment, Romaine transplant growth rate (weekly height, # 2011 trial 2: 48 per media leaves, total leaf area; 1, 2), plant harvest treatment, Romaine trial (height, (height, # leaves, total leaf area, root 3: 40 romaine per media length, root and shoot dry wt, root:shoot ratio; - + treatment germinated in 1, pak choi), leaf Brix, NO3 and K - + cooler, Pak choi trial: 48 (preliminary), extract NO3 and K per media treatment 2 32 romaine per media Germination, transplant data (length, # leaves, Feb.-March, treatment aboveground biomass, harvest index) 2012 3 90 romaine per media Potting soil analysis, germination, transplant Feb.-April, treatment (n=30) data (# leaves, length, aboveground biomass, 2012 harvest index)

15 Experiment 1

Experiment 1 was a feasibility study for the practical function of on-farm vermicompost and thermophilic compost in potting media, in comparison to the commercial medium that the farm currently purchases, McEnroe Premium Organic (Table 1). No one medium was expected to perform better than the others; we simply aimed to assess the capacity of the compost-amended media to support germination and adequate plant growth and, consequently, the potential to use on-farm media instead of the purchased commercial medium.

Ingredients in the two on-farm media included vermicompost or thermophilic compost from the same temporal batches sieved to 5 mm. Both compost preparations were added to Canadian Berger sphagnum peat moss and vermiculite. The peat moss and vermiculite were purchased from Martin’s Produce Supplies, Shippensburg, PA. The on-farm media were mixed by hand according to the formula described in Table 1, adapted from a subchapter in On-Farm Composting Handbook entitled "Using compost for container crops and potting mixes" (Natural Resource, Agriculture, and Engineering Service, 1992). All three media were subject to physical analysis using the USDA NRCS (n.d.) Soil Quality Test Kit

Guide bulk density method (water content, bulk density, water-filled pore space and porosity) and chemical analysis by A&L Eastern Laboratory, Chesterfield, VA (pH, soluble salts, solids, moisture, organic matter, total nitrogen, organic nitrogen, ammoniacal nitrogen, carbon, phosphorus, potassium, calcium, magnesium, sulfur, sodium, aluminum, iron, manganese, copper, boron and zinc). The pH levels of all the media were slightly acidic due to the peat moss input, and although the given range from A&L Eastern Laboratory indicated that this slight acidity is optimum in potting media, the truly optimum pH depends on the

16 species being grown and its preferential conditions. Lactuca sativa prefers a pH range of 6.2 to 6.8, and Brassica rapa var. chinensis prefers a pH range of 6.5 to 7.0 (High Mowing

Organic Seeds, 2011; Queensland Government 2010). Both are sensitive to acidic soils.

Thus, we aimed to increase the pH of the media with the addition of lime in subsequent experiments.

Three trials of Winter Density organic romaine lettuce (Lactuca sativa L. var. longifolia) seeds and one trial of Shanghai Green organic pak choi (Brassica rapa var. chinensis) seeds were planted, with equal amounts assigned to each media treatment, as specified in Table 1 and number of seeds planted reflected in Table 2. All trials were seeded within two weeks of one another. Transplants were grown in pseudoreplicated block groups; all transplants within each spatial block group received the same media treatment, and block groups were positioned adjacent to one another in 128-cell flats. The flats were placed adjacent to one another in a plastic-sheeted high tunnel ranging 40-60F during the night and

60-85F during the day, and were spray-irrigated daily or as needed. The seedlings were transplanted when the majority reached the appropriate size (approximately 5 weeks after planting for romaine and 4 weeks after planting for pak choi) into thermophilic compost- amended research beds in pseudoreplicated block groups within the high tunnel.

Aqueous extract foliar sprays were produced by placing ~2.5 kg (5 lbs.) of vermicompost or thermophilic compost into a 150-micron mesh plastic bag and placing this bag in ~10 liters (2.5 gal) of tap water (dechlorinated by aging) in an aerated plastic tank

(Figure 8). A PVC-pipe-based bubbler connected to an air compressor set at 20 psi supplied aeration. After 10-15 minutes, the extract was drained from the valve at the bottom of the tank and poured into a backpack sprayer. No additives were used because our aim was to

17 determine the baseline capabilities of the extract. Vermicompost or thermophilic compost extract was then applied to plants grown in vermicompost or thermophilic compost media, respectively, such that all foliar surfaces were thoroughly moistened. Dechlorinated water was applied to plants grown in the McEnroe commercial medium as a control. All extracts were sprayed at weekly intervals directly following transplantation, and were tested weekly for nitrate and potassium concentrations using Horiba Cardy microprocessor-based readers.

Germination, transplant growth and plant growth data collected from each trial are detailed in Table 2. Germination, the total number of transplants to emerge throughout the seedling phase, was recorded for all trials. For transplant growth data, all transplants in the noted trials were measured for weekly height and number of leaves, and five transplants were randomly selected for weekly total leaf area. Romaine trial 1 plants were harvested 14 weeks after planting, and Pak choi trial plants were harvested 12 weeks after planting (Romaine trials 2 and 3 plants were not measured for harvest data due to time constraints). For plant growth data collected at harvest, all plants in the noted trials were measured for root length, and five plants were randomly selected for measurement of total leaf area, root and shoot dry weights and root:shoot ratios (using destructive sampling). Height was measured as the vertical distance between the soil line and the highest living part of the plant. Total leaf area was measured per plant by summing the products of the length and width of all leaves. Root length was measured as the length of the longest root. These were all measured with a simple ruler. Numbers of leaves per plant were simply counted, and dry weights were determined using a weighing balance after cutting the plants at the soil line. Preliminary leaf Brix (sugar content), nitrate and potassium levels were collected from individual plants in Romaine trials

1 and 3 and the Pak choi trial. Brix was measured using a refractometer, and leaf nitrate and

18 potassium concentrations were measured using Horiba Cardy microprocessor-based readers.

Data were analyzed in Microsoft Excel using chi-squared tests for germination and one-way

ANOVA tests for plant growth and extract parameters.

Experiment 2

Experiment 2 aimed to identify the most effective concentration of vermicompost and thermophilic compost in on-farm potting media, and to assess the use of the blood meal mix as a nutrient amendment (Table 1). No one concentration level or compost media treatment was expected to perform better than the others, but all media containing the blood meal mix were expected to perform better than those without. Primarily, this experiment was a pre-trial for Experiment 3, the objective of which was to determine the concentration of vermicompost to be used. Because of time constraints on the need to begin Experiment 3, the selection of compost concentration for Experiment 3 was based on germination rather than on transplant growth results from this experiment. However, we also evaluated the impact of different concentrations of compost on transplant growth, compared vermicompost to thermophilic compost media, and assessed on-farm media in relation to the McEnroe commercial medium.

As shown in Tables 1 and 3, McEnroe commercial medium and 12 on-farm media were tested, on-farm media varying by nutrient treatment (base or base+blood meal mix), compost type (vermicompost or thermophilic compost) and compost concentration (10%,

20%, or 30%). For the purposes of this experiment, we assumed that using a concentration greater than 0% of compost would produce better results than using no compost in the on- farm potting media, but Experiment 3 further addressed this matter. Vermicompost and

19 thermophilic compost used in Experiments 2 and 3 were from the same temporal batches.

Vermicompost had been removed from the bin, uniformly mixed through the sifting process, and stored for a period of 2 months. The on-farm media were mixed with a cement mixer

(Figure 8) according to the formulas described in Table 1. The peat moss base mixture, including lime, was adapted from Jack et al. (2011). Soil Doctor Pulverized garden lime (3 lbs. yd-3 or 1.78 kg m-3) was used to buffer the acidity of peat moss. The blood meal mix was adapted from Biernbaum (2011) and Leonard and Rangajaran (2007). It contained blood meal as a nitrogen amendment, greensand as a potassium amendment and bone char as a phosphorus amendment at 2:2:1 volume/volume ratio (respectively), all from the Fertrell

Company. After mixing, each medium was watered and left to sit for two days prior to seeding to allow the chemical properties to stabilize and the microorganisms to activate.

Table 3. Media treatments shown by variable.

10% 20% 30% Base Base + 10% VC Base + 20% VC Base + 30% VC Base + 10% TC Base + 20% TC Base + 30% TC BM Base + BM mix + 10% VC Base + BM mix + 20% VC Base + BM mix + 30% VC mix Base + BM mix + 10% TC Base + BM mix + 20% TC Base + BM mix + 30% TC McEnroe

20

Figure 8. Panel A shows the cement mixer with a batch of potting soil. Panel B shows the compost-filled mesh bag during the extraction process in the aerated extraction tank. Thirty-two Winter Density romaine lettuce seeds were planted into each media treatment, as specified in Tables 1 and 2. Transplants were grown in pseudoreplicated block groups; all transplants within each spatial block group received the same media treatment, and block groups were positioned adjacent to one another in 128-cell flats, as in Experiment

1. The flats were placed adjacent to one another on 70F-heating mats in a plastic-sheeted greenhouse ranging 40-60F during the night and 60-95F during the day, and were spray- irrigated daily or as needed.

Germination and transplant growth data collected are detailed in Table 2. Seeds were recorded as either germinating or not. All transplants were cut at the soil line 39 days after planting, and measured for number of leaves, length, aboveground biomass and harvest index. Length was measured as the distance between the soil line and the growing tip by flattening the tallest leaf against a ruler. Aboveground biomass was determined by drying the cut transplants and weighing them. Harvest index was calculated as aboveground

21 biomass/length. Data were analyzed using program R (R Development Core Team, 2006).

Generalized linear mixed-effects models were used for response variables with binomial distributions (germination), and linear mixed-effects models were used for variables with normal distributions (number of leaves, length, aboveground biomass, and harvest index).

Significance was assessed with log-likelihood statistics for the generalized linear models and

F-tests for the linear models, using Type II sum of squares procedures for both. McEnroe commercial medium germination data were included in the generalized linear mixed-effects models, but McEnroe transplant data were not included in the linear mixed-effects models.

Experiment 3

Experiment 3 was designed to assess the effects of adding 10% vermicompost to on- farm media containing a base and blood meal mix, of substituting peat with coir as the base, and of treating these media with vermicompost extract via foliar spray on transplant germination and growth (Table 1). We hypothesized that (1) media with 10% vermicompost would perform better than the control (0% vermicompost) in terms of transplant growth, (2) vermicompost extract foliar sprays would positively affect transplant growth and (3) coir- based media would not significantly differ from peat-based media in terms of transplant germination and growth.

Four on-farm media treatments were tested, varying by base (peat moss or coir) and vermicompost concentration (unamended: 0% or amended: 10%), as described in Table 4.

The unamended media were the control treatments. Media treatments were mixed with a cement mixer (Figure 8) according to the formulas described in Table 1. Because of time constraints at the beginning of the experiment, the selection of vermicompost concentration

22 was based on an interview with a field expert (Allison Jack, personal communication,

January 30, 2012) and germination, rather than on plant growth results from Experiment 2.

Thus, 10% sieved vermicompost was used for the vermicompost media. The peat moss base mixture and blood meal mix were equivalent to those described in Experiment 2. The coir- based media directly substituted coir from Ironwood Nursery, Williamsport, PA for peat moss in otherwise identical mixtures to the peat media. After mixing, each medium was watered and left to sit for one week prior to seeding, to allow the chemical properties to stabilize and the microorganisms to activate. Sub-samples of each media treatment were subject to physical analysis using the USDA NRCS (n.d.) Soil Quality Test Kit Guide bulk density method and chemical analysis by A&L Eastern Laboratory, as in Experiment 1.

Table 4. Media treatments shown by variable.

Control Vermicompost Peat Peat base + BM mix Peat base + BM mix + 10% VC Coir Coir base + BM mix Coir base + BM mix + 10% VC

Winter Density romaine seeds were planted in a completely randomized block design comprising of ten randomized blocks. Each block consisted of three replicates of the four media treatments. Figure 9 shows an example block. The seeds were planted in triplicate (in

3 adjacent cells) to account for germination being below 100%. Thus, 90 seeds total were planted per media treatment, but 30 transplants were assessed per media treatment. When more than one seed germinated per triplicate, the one to be measured was randomly selected, and when no seeds germinated, zeros were recorded for that data point. The 128-cell flats were placed adjacent to one another on 70F-heating mats in a plastic-sheeted greenhouse ranging from 40F to 95F, and were spray-irrigated daily or as needed.

23

Figure 9. An example of the spatial layout of a block. Vermicompost extract was produced using equivalent methods to those in Experiment

1 (Figure 8). It was sprayed foliarly at weekly intervals; however, unlike in Experiment 1, treatments started directly after seeding to assess effects on transplants. Using a split-plot design, extract foliar application alternated by block (Block A was treated, Block B was not treated, etc.) such that half of the cells were treated and the other half were not treated.

Transplant data collection methods were equivalent to those in Experiment 2 (Table

2). Germination was recorded as whether or not each of the 90 seeds per media treatment resulted in an emerged transplant. Randomly selected or germination-determined transplants

(potentially 30 per media treatment, as described previously) were cut at the soil line 39 days after planting, and measured for number of leaves, length, aboveground biomass and harvest

24 index. Data analysis employed the same methods as in Experiment 2, but with Block added to the analyses as a random variable.

Results & Discussion

The results are presented by experiment, including potting media analyses (when applicable), germination and plant growth. In order to facilitate understanding of how the experiments connect to and build upon one another, some interpretation will accompany the presentation of results. A more global discussion that considers how these results related to previous studies will follow.

Since the physical and chemical compositions of the vermicompost and thermophilic compost produced on-farm at DCF and their food waste feedstocks (Table 5) are relevant to multiple experiments, we address them first. Both vermicompost and thermophilic compost had typical pH, soluble salts and total nitrogen levels (Agricultural Analytical Services

Laboratory, n.d.; Table 5). Also, their low carbon:nitrogen ratios indicate that they can break down organic nitrogen into inorganic nitrogen, which is readily available for plant absorption. However, their solids concentrations were below the typical 50-60%, and their moisture concentrations were above the typical 40-50% for finished compost, indicating that they were not quite mature (Agricultural Analytical Services Laboratory, n.d.).

Vermicompost contained higher levels of soluble salts, organic matter and nearly every nutrient, excluding a few of the trace elements, which is attributed to the worm castings’ nutrient richness. Conversely, the organic matter, total nitrogen and carbon levels in the vermicompost feedstock were much lower than in the thermophilic compost feedstock, which was also relatively acidic.

25 Table 5. Physico-chemical analyses of on-farm vermicompost (VC) and thermophilic compost (TC) and their food waste feedstocks.

VC TC VC feedstock TC feedstock pH 7.3 7.3 7.8 4.2 Soluble salts (mmhos/cm) 3.68 2.16 3.52 7.84 Solids (%) 42.6 42.4 42.5 25.3 Moisture (%) 57.4 57.6 57.5 74.7 Organic matter (% dw*) 35.2 33.3 29.8 95.0 Total nitrogen (% dw) 1.73 1.43 0.8 3.9 Organic nitrogen (% dw) 1.73 1.42 Ammonium N (mg/kg dw) 5.0 5.0 Carbon (% dw) 19.9 17.8 9.3 52.7 Carbon:nitrogen ratio 11.50 12.50 11.50 13.40 Phosphorus (% dw) 0.744 0.570 Potassium (% dw) 0.80 0.48 Calcium (% dw) 3.65 3.58 Magnesium (% dw) 1.16 0.74 Sulfur (% dw) 0.23 0.45 Sodium (mg/kg dw) 750 432 Aluminum (mg/kg dw) 13035.80 10749.09 Iron (mg/kg dw) 15621.46 16135.99 Manganese (mg/kg dw) 850.33 988.50 Copper (mg/kg dw) 30.96 37.76 Zinc (mg/kg dw) 27.10 96.50 *dw=dry weight

Experiment 1

McEnroe commercial potting medium contained the highest levels of most nutrients compared to both compost media (Table 6); however, its concentrations of nitrogen, nitrate, potassium, calcium, magnesium, sulfur and sodium were greater than the normal range, as designated by A&L Eastern Laboratories (2012). This suggests that McEnroe could be providing more nutrients than germinating seeds and transplants need. Also, its very high concentration of soluble salts could cause salinity stress. The vermicompost medium contained the next highest nutrient and salinity levels, its concentrations of soluble salts, nitrogen, calcium, magnesium, manganese, boron and sulfur in optimum levels within the normal range. The thermophilic compost medium contained the lowest nutrient and salinity levels, which is attributed to the lower nutrient levels of the thermophilic compost input itself compared to the vermicompost input (Table 5). Physically, the lower bulk density and higher

26 water content, water-filled pore space and porosity of the on-farm media indicate enhanced aeration and water retention compared to McEnroe, which suggests that they could be better suited to support transplant growth. This is attributed to not only the aeration-promoting soil particle stability of the on-farm compost inputs, but also the use of 1/3 v/v vermiculite in the media, which lightened them up considerably.

Table 6. Experiment 1 physico-chemical analyses of vermicompost-amended (VC), thermophilic compost-amended (TC) and McEnroe commercial (M) media.

1/3 VC 1/3 TC M Normal range Low High Bulk Density (g/cm3) 0.184 0.164 0.416 - - Soil water content (g/g) 4.165 4.774 1.605 - - Soil water-filled pore 82.5 83.2 79.2 - - space (%) Soil porosity (%) 93.0 93.8 84.3 - - pH 5.8 5.9 5.9 5 6 Soluble salts 2.39 1.25 5.00 0.7 3 (mmhos/cm) Nitrogen (ppm) 173 81 413 40 200 Ammoniacal N (ppm) 2 2 1 0 30 Nitrate N (ppm) 171 79 412 40 200 Phosphorus (ppm) 70.1 41.4 29.4 5 30 Potassium (ppm) 329.0 136.0 672.0 50 200 Calcium (ppm) 151 105 484 80 200 Magnesium (ppm) 76 46 237 30 100 Iron (ppm) 13.7 12.8 14.4 15 40 Manganese (ppm) 18.2 17.3 3.4 5 30 Zinc (ppm) 4.6 4.3 5.5 5 30 Copper (ppm) 0.3 0.3 1.0 2 20 Boron (ppm) 0.8 1.0 0.7 0.2 0.9 Sulfur (ppm) 47 20 358 16 200 Sodium (ppm) 130 84 125 0 80 Aluminum (ppm) 1.9 2.2 0.6 0 3

Germination rates were 80-94% in all trials and potting media, with the exception of

Romaine 1 (Figure 10). Since all the media treatments in this trial had low germination, this is attributed to external environmental factors, such as the severe overcast that persisted during the germination period, which provided unfavorable conditions. Germination rates

2 were similar across the media treatments for each trial (2 =1.1, 4.4, 3.2, 1.3, respectively,

27 P>0.1 for each). Since McEnroe commercial medium is a well-established medium with enhanced constituents and this experiment was DCF’s first practical application of its vermicompost and thermophilic compost in potting media, we could not expect the on-farm media to surpass the commercial medium in terms of seed nourishment and plant growth.

Thus, the lack of significant differences in germination was considered a favorable result because it indicates that the on-farm compost media could potentially replace the commercial medium without sacrificing productivity, at least in terms of germination.

Figure 10. Experiment 1 germination (±standard error of individual cells) of the vermicompost (VC), thermophilic compost (TC) and McEnroe commercial media (M) treatments. With a few exceptions among the parameters, plants grown with McEnroe commercial medium and the control extract treatment generally had higher yields than plants grown with the vermicompost or thermophilic compost media and respective extract foliar sprays, but not always significantly (Table 7; Figures 11 and 12). The sample size of

Romaine 2 transplants was larger than Romaine 1 transplants, and their growth trends were more consistent with observational trends of Romaine 3 and Pak choi transplants. Romaine 2

28 McEnroe transplants had significantly higher daily height and leaf growth rates than vermicompost and thermophilic compost transplants, but only marginally higher daily total leaf area growth (one-way ANOVA; Table 7, “Transplant growth rate” section). The somewhat opposing trend of the Romaine 1 transplants is attributed not only to the unusual environmental germination conditions, but also to the variability of nutrient and microbial composition within batches of vermicompost, which acted in the favor of the vermicompost medium in this case. Generally, since McEnroe contains compost and several minerals, its superior transplant growth could be attributed to increased availability of nutrients.

Additionally, between the two on-farm media, the relatively higher growth rate of vermicompost transplants over thermophilic compost transplants is attributed to higher nutrient levels of the vermicompost medium. The harvested plants (Romaine 1 and Pak choi) largely did not differ significantly among groups (one-way ANOVA; Table 7, “Harvested plant growth” section).

29 Table 7. Experiment 1 transplant growth rate and harvested plant growth (mean±standard error).

Parameter Trial 1/3 VC 1/3 TC M Transplant growth rate Height (mm/day) Romaine 1*** 3.20±0.22 0.93±0.12 1.89±0.28 Romaine 2*** 1.83±0.08 1.50±0.12 3.76±0.21 Leaves (lpd) Romaine 1** 0.18±0.02 0.12±0.02 0.21±0.02 Romaine 2*** 0.20±0.01 0.17±0.01 0.27±0.01 Total leaf area Romaine 1** 3.71±0.29 1.07±0.27 3.67±0.75 (cm2/day) Romaine 2 2.88±0.60 2.68±0.50 3.46±0.70 Harvested plant growth Height (mm) Romaine 1 125.74±9.05 159.53±11.12 134.25±12.92 Pak choi 134.7±8.52 159.8±6.77 160.7±10.23 # leaves Romaine 1 26±4.03 23.8±1.02 29.4±3.25 Pak choi* 14±1.00 16.2±1.43 20.67±1.86 Root length (mm) Romaine 1 155.65±5.89 142.05±10.79 153.69±9.79 Pak choi 266.4±12.04 234.9±15.86 229.6±17.71 Root dw (g) Romaine 1 0.76±0.18 0.68±0.08 0.89±0.26 Pak choi** 0.44±0.05 0.56±0.02 0.81±0.12 Shoot dw (g) Romaine 1 24.22±10.96 33.88±6.69 50.61±16.21 Root:shoot ratio Romaine 1 0.06±0.02 0.02±0.00 0.04±0.02 Total leaf area (cm2) Romaine 1 3518.43±1203.16 3927.85±391.49 5328.66±1484.72 Differences among groups: *significance at P<0.05, **significance at P<0.01, ***significance at P<0.001 (one- way ANOVA)

Figure 11. Experiment 1 Romaine 2 transplants 28 days after planting (DAP) grown in vermicompost, thermophilic and McEnroe commercial media, respectively.

30

Figure 12. The 5 randomly selected Romaine 1 plants per media treatment in Experiment 1 that were measured for dry weights, harvested at 96 DAP; the top row was grown with vermicompost, the second row was grown with thermophilic compost and the bottom row was grown with McEnroe commercial medium. We were unable to verify treatment effects due to the possibility of spatial block effects associated with pseudoreplication, but spatial block effects were unlikely during the transplant stage and harvest data, although observationally useful, were largely statistically inconsequential. However, harvest data could have been affected by physical differences along the substrate, whereby some areas were more compacted than others, hindering root growth to different degrees. Also, the cold temperatures stunted plant growth. Therefore, the effects of the different potting media and aqueous extract foliar sprays on crop performance after transplantation into greenhouse substrates remain somewhat uncertain. Lastly, we hypothesized that the compost media would require nutrient amendments in order to perform more comparably to McEnroe commercial medium; thus the nutrient-rich blood meal mix was applied and tested in Experiment 2.

Although the nitrate and potassium levels were significantly different among experimental and control groups for the aqueous extract foliar sprays (P<0.001 for both

31 nitrate and potassium), with vermicompost extract containing the highest levels and thermophilic compost containing the next highest levels (Figure 13), we observed no physical evidence of treatment effects on differences physical plant growth or health. This might be because microbial activity in the extracts was insufficient or that the spraying frequency was inadequate.

350

300

NO -

NO33 250 KK+ 200

150

Concentration(ppm) 100

50

0 VC TC Control Spray treatment

Figure 13. Experiment 1 nitrate and potassium concentrations (mean±standard error) in the vermicompost extract, thermophilic compost extract and control (dechlorinated water). Preliminary analyses showed that plants grown with vermicompost media generally had the highest relative Brix, nitrate and potassium levels (Table 8), but determining the biological significance of this is beyond the scope of this study.

32 Table 8. Experiment 1 Brix, nitrate and potassium measurements of romaine and pak choi leaves of randomly selected individual plants.

Parameter Trial 1/3 VC 1/3 TC M Brix Romaine 1 5.08 3.82 4.58 Romaine 3 15.88 13.55 6.32 Pak choi 7.06 6.57 6.32 - NO3 (ppm) Romaine 3 1900 2400 1600 Pak choi 1100 310 530 K+ (ppm) Romaine 3 3100 2600 2600 Pak choi 3500 2300 2500

Experiment 2

Out of the three tested variables, nutrient treatment (base or blood meal mix), compost type (vermicompost, thermophilic compost, or McEnroe commercial medium) and compost concentration (10%, 20%, or 30%), only compost type had a significant main effect

2 on germination (1 =18.1, P<0.001; Figure 14; Table 9). Vermicompost media had the lowest germination rate, followed by thermophilic compost, and McEnroe had the highest

(Figure 14). The lower germination of on-farm media, especially the vermicompost medium, could be associated with the potential immaturity of the composts (Table 5). Although compost concentration did not significantly affect germination, within each group, 10% compost always had the highest relative germination, 20% nearly always had the lowest, with

30% nearly always in between. Given the need to make a decision based on these study results and the scientific assertion that concentrations above 20% can inhibit drainage obtained from an interview with a field expert (Allison Jack, personal communication,

January 30, 2012), 10% was chosen as the concentration to be used in Experiment 3.

33 Base-VC Base-TC BM-VC BM-TC M 100% 90% 80%

70% 60% 50%

40% Germination 30% 20% 10% 0% 10 20 30 Compost concentration (%)

Figure 14. Experiment 2 germination (mean±standard error of individual cells) of base+vermicompost (Base-VC), base+thermophilic compost (Base-TC), base+blood meal mix+vermicompost (BM-VC) and base+blood meal mix+thermophilic compost (BM-TC) media treatments with 10%, 20% and 30% compost, and of McEnroe commercial medium (M).

Table 9. Experiment 2 tests of significance of the main effects of nutrient treatment, compost type, and compost concentration on the germination response.

Predictor 2 df P Nutrient treatment (base, BM mix, M nutrients) 0.3 1 0.597 Compost type (VC, TC, M compost) 18.1 1 <0.001 Compost concentration (10%, 20%, 30%, M compost concentration) 1.4 1 0.244

In general, media with blood meal mix had higher plant yields than media with only the base (Figure 15). Media with vermicompost had higher yields than media with thermophilic compost, and media with 20%-30% compost had higher yields than media with

10% (Figure 15). The blood meal mix nutrient treatment had significantly positive main effects on all transplant growth responses (Table 10). Vermicompost transplants had significantly higher numbers of leaves, aboveground biomasses and harvest indices than thermophilic compost transplants. These effects are attributed to the increased availability of

34 more exchangeable nutrients provided by the vermicompost and blood meal mix. The stimulation of vermicompost microbial activity by blood meal mix likely contributed to nutrient release (Leonard & Rangarajan, 2007). Additionally, we infer that media with higher concentrations of compost contained higher nutrient levels, which explains why these media had higher yields, but at the 30% concentration, the media could have become more waterlogged. Thus, 20% compost was ideal plant growth. Compost type effects on number of leaves and length depended on nutrient treatment effects, as indicated by a significant compost*treatment interaction; blood meal mix had a greater positive effect on thermophilic compost transplant yields than on vermicompost transplant yields (Figure 16). This is attributed to the lower initial nutrient levels in thermophilic compost compared to vermicompost, which made the impact of the added nutrients in blood meal mix larger.

Overall, this experiment affirmed the use of blood meal mix and vermicompost for plant growth, in on-farm potting media. Most blood meal mix-amended media performed similarly to McEnroe commercial medium, with the 20% vermicompost+blood meal mix medium in particular performing notably better in terms of number of leaves, aboveground biomass and harvest index (Figure 15).

35 Base-VC Base-TC Base-VC Base-TC BM-VC BM-TC BM-VC BM-TC M M 11 160 140 10

120

9 100 8 80

# leaves # 60 7 Length (mm) Length 40 6 20 5 0 10 20 30 10 20 30 Compost concentration (%) Compost concentration (%)

Base-VC Base-TC Base-VC Base-TC BM-VC BM-TC BM-VC BM-TC M M

0.30 0.025

0.25 0.020

0.20 0.015 0.15 0.010

0.10 AG biomass (g) biomass AG

0.05 (g/cm) index Harvest 0.005

0.00 0.000 10 20 30 10 20 30 Compost concentration (%) Compost concentration (%)

Figure 15. Experiment 2 number of leaves, length, aboveground biomass and harvest index (mean±standard error) of base+vermicompost (Base-VC), base+thermophilic compost (Base- TC), base+blood meal mix+vermicompost (BM-VC) and base+blood meal mix+thermophilic compost (BM-TC) media treatments with 10%, 20% and 30% compost, and of McEnroe commercial medium (M).

36 Table 10. Experiment 2 tests of significance of the main and interactive effects on the number of leaves, length, aboveground biomass, and harvest index responses.

Response Predictor F df P Number of Nutrient treatment (base, BM mix) 197.0 1,210 <0.001 leaves Compost type (VC, TC) 23.1 1,210 <0.001 Compost concentration (10%, 20%, 30%) 7.5 1,210 0.007 Nutrient treatment*compost type 5.8 1,210 0.017 Nutrient treatment*compost concentration 3.7 1,210 0.057 Compost type*compost concentration 4.2 1,210 0.042 Nutrient treatment*compost type*compost concentration 6.6 1,210 0.011 Length Nutrient treatment (base, BM mix) 918.3 1,211 <0.001 Compost type (VC, TC) 4.4 1,211 0.038 Compost concentration (10%, 20%, 30%) 1.6 1,211 0.206 Nutrient treatment*compost type 107.4 1,211 <0.001 Nutrient treatment*compost concentration 13.8 1,211 <0.001 Compost type*compost concentration 0.6 1,211 0.431 Nutrient treatment*compost type*compost concentration 18.9 1,211 <0.001 AG Nutrient treatment (base, BM mix) 271.8 1,210 <0.001 biomass Compost type (VC, TC) 22.1 1,210 <0.001 Compost concentration (10%, 20%, 30%) 13.7 1,210 <0.001 Nutrient treatment*compost type 2.3 1,210 0.129 Nutrient treatment*compost concentration 0.0 1,210 0.848 Compost type*compost concentration 3.3 1,210 0.073 Nutrient treatment*compost type*compost concentration 1.7 1,210 0.188 Harvest Nutrient treatment (base, BM mix) 57.6 1,210 <0.001 index Compost type (VC, TC) 26.5 1,210 <0.001 Compost concentration (10%, 20%, 30%) 16.5 1,210 <0.001 Nutrient treatment*compost type 2.1 1,210 0.147 Nutrient treatment*compost concentration 0.9 1,210 0.343 Compost type*compost concentration 3.0 1,210 0.085 Nutrient treatment*compost type*compost concentration 0.6 1,210 0.439

37

Figure 16. Experiment 2 vermicompost transplants grown with the base nutrient treatment (under first two wooden labels) and blood meal mix nutrient treatment (under the third wooden label; Panel A), and thermophilic compost transplants grown with the base nutrient treatment (Panel B above) and blood meal mix nutrient treatment (Panel B below) 35 DAP. Although the treatments in this experiment were spatially pseudoreplicated, it is unlikely that the observed treatment effects were caused by random spatial effects because in

Experiment 3, which was randomized and properly replicated, spatial block effects were found to be largely insignificant (P>0.05 for most parameters and predictors). This experiment was conducted in essentially the same location and spatial arrangement as

Experiment 3, so that spatial effects would likely have been revealed by both experiments if they were important determinants of plant germination and growth. Thus it is most likely that the effects observed in Experiment 2 reflect true treatment effects rather than random spatial variation.

38 Experiment 3

Media containing 10% vermicompost contained higher nutrient levels than media containing no vermicompost, but most of the distinct nutrient concentrations of the vermicompost media were lower than their respective optimum potting media levels (Table

11; A&L Eastern Laboratories, Inc., 2012). Ammoniacal nitrogen concentrations of the vermicompost media were excessively high. This suggests that the vermicompost batch was not fully decomposed (Grubinger, 2012), which is consistent with results of the vermicompost physico-chemical analysis. Specifically, the presence of high levels of ammoniacal nitrogen is attributed to the failure of the microorganisms within the vermicompost system to nitrify ammonia from worm excretions and the feedstock of the batch before it was extracted from the system (Lee, 1985). Peat-based media contained higher concentrations of phosphorous, iron and boron, and coir-based media contained higher concentrations of nitrogen, potassium, magnesium, zinc, sulfur and sodium (Table 11). Thus, coir media were richer in nutrients. Coir media had higher alkalinity than peat media. This is likely due to differences in underlying acidity between coir and peat. Lime was applied to both treatments to be consistent, but whereas it acted to neutralize the acidity of the peat moss, it caused the neutral coir to become basic. Physically, coir media had greater water content and water-filled pore space than peat media, indicating its higher water retention capacity. Physical aspects favored vermicompost media in some respects and unamended media in others for reasons that are somewhat uncertain, which would require further replication.

39 Table 11. Experiment 3 physico-chemical analyses of peat- and coir-based media with and without vermicompost.

Peat Peat, Coir Coir, Normal range VC VC Low High Bulk Density (g/cm3) 0.097 0.112 0.081 0.109 - - Soil water content (g/g) 1.042 0.970 2.423 1.832 - - Soil water-filled pore 10.5 11.3 20.2 20.7 - - space (%) Soil porosity (%) 96.3 95.8 97.0 95.9 - - pH 6.3 6.9 8.0 7.5 5 6 Soluble salts 0.37 1.40 0.96 1.40 0.7 3 (mmhos/cm) Nitrogen (ppm) 4 132 11 141 40 200 Ammoniacal N (ppm) 4 58 9 53 0 30 Nitrate N (ppm) 0 74 2 88 40 200 Phosphorus (ppm) 2.4 9.0 1.1 6.8 5 30 Potassium (ppm) 21.7 112.0 140.0 256.0 50 200 Calcium (ppm) 31 76 36 63 80 200 Magnesium (ppm) 16 38 18 39 30 100 Iron (ppm) 8.5 6.4 4.5 4.0 15 40 Manganese (ppm) 3.8 6.1 4.7 5.9 5 30 Zinc (ppm) 0.8 2.5 2.6 3.9 5 30 Copper (ppm) 0.3 0.3 0.3 0.3 2 20 Boron (ppm) 0.3 0.2 0.0 0.1 0.2 0.9 Sulfur (ppm) 13 30 18 31 16 200 Sodium (ppm) 25 51 63 87 0 80 Aluminum (ppm) 1.8 1.1 2.0 1.6 0 3

The application of vermicompost to the potting media and of vermicompost extract to leaves both had significant negative main effects on germination (Figure 17; Table 12). The high concentrations of ammoniacal nitrogen in vermicompost media likely harmed germinating seeds due to ammonium phytotoxicity (California Compost Quality Council,

2001). With respect to vermicompost extract foliar spray, its application could have waterlogged the media and seeds and exposed them to more ammonia. Main effects of the media base were insignificant; thus, despite the alkaline pH levels of coir media in relation to peat media, germination was likely not affected by this difference in pH. These germination data suggest that coir could substitute peat effectively as a potting media base. All interactive effects were insignificant.

40 80% 80% 70% 70% Control 60% 60% Peat

VC extract 50% Coir 50% 40% 40%

30% Title Axis 30% Germination 20% 20% 10% 10% 0% 0% 0 10 0 10 VC concentration (%) VC concentration (%)

Figure 17. Experiment 3 germination (mean±standard error) of peat-based and coir-based media and non-extract-treated (control) and extract-treated media with 0% (control) and 10% vermicompost.

Table 12. Experiment 3 tests of significance of the main and interactive effects on the germination response.

Predictor 2 df P Base (peat, coir) 0.7 1 0.414 VC concentration (0%, 10%) 58.0 1 <0.001 Extract treatment (no, yes) 4.8 1 0.029 Base*VC concentration 0.5 1 0.502 Base*extract treatment 1.8 1 0.179 VC concentration*extract treatment 2.4 1 0.119 Base*VC concentration*extract treatment 0.6 1 0.432

The main effects of concentration and base media on all growth parameters were significant, favoring 10% vermicompost over the control and peat over coir (Figure 18; Table

13; Figure 19). One explanation for this is that vermicompost treatment itself positively impacted transplant growth. Another plausible explanation is that seed mortality in the vermicompost media confounded the results in terms of plant selection during germination, such that seeds that did germinate could have been the most robust, growing into the largest transplants, and seeds that failed to germinate would have grown into smaller transplants.

41 However, no direct evidence of a correlation between germination and growth exists in this case, whereas both the enhanced nutrient levels of vermicompost media (Table 11) and trends in the literature support the first explanation whereby the vermicompost treatment positively impacted transplant growth (Edwards & Burrows, 1988; Buckerfield et al., 1999;

Arancon et al., 2007). Specifically, vermicompost likely contained growth-promoting microorganisms and increased nutrient availability for plant absorption, especially nitrate.

The alkaline pH levels of the coir media (Table 11) likely inhibited transplant growth because optimal plant growth is reached with soil pH levels of 5.0 to 6.5 and Lactuca sativa prefers 6.2 to 6.8, as mentioned previously (Goh & Haynes, 1977; High Mowing Organic

Seeds, 2011). Atiyeh et al. (2000b) found that the alkalinity of coir media reduced germination of pepper and tomato, similar to the results in this study. Thus, without the addition of lime, the coir media might have performed better, perhaps as well as the peat media. Interactive effects were minimal, as can be seen by the similar slopes of the lines

(Figure 18). Only number of leaves and length demonstrated a strong interactive effect whereby base media effects determined concentration effects; the vermicompost had a greater positive effect on coir transplants than on peat transplants (Figure 18; Table 13).

Vermicompost extract foliar sprays did not significantly impact transplant growth (Table 13).

Lastly, although the experimental design was randomized and properly replicated, spatial block effects were essentially insignificant, as mentioned previously (P>0.05 for most parameters and predictors).

42 9 100 90 8 80

7 70

6 60 50 5 Peat Peat # leaves # 40

4 Coir (mm) Length 30 Coir 20 3 10 2 0 0 10 0 10 VC concentration (%) VC concentration (%)

0.35 0.040 0.035

0.30

0.25 0.030 0.025 0.20 0.020 0.15 0.015 Peat Peat AG biomass (g) biomass AG 0.10 0.010

Coir (g/cm) index Harvest Coir 0.05 0.005 0.00 0.000 0 10 0 10 VC concentration (%) VC concentration (%)

Figure 18. Experiment 3 number of leaves, length, aboveground biomass and harvest index (mean±standard error) of peat-based and coir-based media with 0% vermicompost (control) and 10% vermicompost.

43 Table 13. Experiment 3 tests of significance of the main and interactive effects on the number of leaves, length, aboveground biomass, and harvest index responses.

Response Predictor F df P Number of Base (peat, coir) 122.9 1,60 <0.001 leaves VC concentration (0%, 10%) 68.0 1,60 <0.001 Extract treatment (no, yes) 0.3 1,2 0.636 Base*VC concentration 23.8 1,60 <0.001 Base*extract treatment 1.4 1,60 0.247 VC concentration*extract treatment 0.0 1,60 0.879 Base*VC concentration*extract treatment 0.0 1,60 0.891 Length Base (peat, coir) 92.7 1,60 <0.001 VC concentration (0%, 10%) 147.1 1,60 <0.001 Extract treatment (no, yes) 5.1 1,2 0.153 Base*VC concentration 8.0 1,60 0.006 Base*extract treatment 3.4 1,60 0.070 VC concentration*extract treatment 0.4 1,60 0.506 Base*VC concentration*extract treatment 0.5 1,60 0.474 AG Base (peat, coir) 41.1 1,60 <0.001 biomass VC concentration (0%, 10%) 105.1 1,60 <0.001 Extract treatment (no, yes) 17.9 1,2 0.052 Base*VC concentration 0.4 1,60 0.541 Base*extract treatment 0.4 1,60 0.516 VC concentration*extract treatment 0.2 1,60 0.663 Base*VC concentration*extract treatment 0.0 1,60 0.865 Harvest Base (peat, coir) 17.1 1,60 <0.001 index VC concentration (0%, 10%) 34.7 1,60 <0.001 Extract treatment (no, yes) 0.1 1,2 0.822 Base*VC concentration 1.5 1,60 0.225 Base*extract treatment 0.0 1,60 0.825 VC concentration*extract treatment 0.1 1,60 0.808 Base*VC concentration*extract treatment 0.0 1,60 0.986

44

1. coir-control 2. coir-VC 3. peat-control 4. coir-control 5. peat-VC 6. coir-control

1. peat-VC 2. coir-control 3. peat-control 4. coir-control 5. peat-control 6. coir-VC 7. coir –control 8. peat-VC 9. peat-control 10. coir-VC

Figure 19. Experiment 3 transplants from various media treatment groups organized in their randomized blocks 39 DAP. Therefore, the application of vermicompost to potting media negatively impacted germination (Figure 17), but positively impacted transplant growth (Figure 8). This partially supports the first hypothesis, which stated that vermicompost media would perform better than unamended media in terms of transplant growth. Furthermore, the application of vermicompost extract foliar sprays negatively impacted germination (Figure 17) and did not

45 enhance transplant growth (Table 13), providing no support for the second hypothesis, which stated that extract application would positively impact transplant growth. Lastly, coir performed as well as peat as a potting media base in terms of germination (Figure 17), but not in terms of transplant growth (Figure 18). This partially supports the third hypothesis, which stated that coir media would not significantly differ from peat media in terms of transplant germination and growth.

Discussion

These experiments, in addition to previous studies, indicate the potential that vermicompost shows for enhancing plant productivity and health. Vermicompost produced on a small-scale working farm and fed by localized organic wastes, showed promise when applied in potting media for vegetable transplant growth. Vermicompost-amended potting media outperformed both unamended and thermophilic compost-amended media in terms of transplant growth following germination. This is attributed to enhanced nutrient availability and richness, and increased activity of beneficial microorganisms.

However, the suitability of composts as potting soil amendments or aqueous extract foliar sprays depends on their particular nutrient and microbial contents. Distinct differences exist between specific compost preparations, even when composting is performed with the same technique, largely because preparations vary in the type of feedstock added to the compost. This can include differences in nutrient content and microbial communities, which can in turn influence plant growth, transplant quality, and field performance (Atiyeh et al.,

2000c; Jack et al., 2011). One way to control for some of these differences is to consider common feedstocks (Edwards & Burrows, 1988; Jack, 2010).

46 It is unclear how food waste-based vermicomposts compare to manure-, paper-, or sewage-based vermicomposts because of the disproportionately high amount of studies that have focused on manure-based vermicompost, but food waste-based vermicompost seems to perform similar ecosystems services to manure-based vermicompost. Arancon et al. (2004) reported that heights, numbers of buds, and numbers of flowers of peppers grown in food waste-based vermicompost-amended media were not significantly greater than those grown in unamended media. Atiyeh et al. (2000c) reported that pig manure-based vermicompost performed better than food waste-based vermicompost in terms of plant growth enhancement. Therefore, the shortcomings of the food waste-based vermicompost used in this study were accepted, and the beneficial aspects were considered forms of plant support rather than absolute forms of fertilization or disease suppression.

Our study found that vermicompost amendments to potting media reduced germination of lettuce transplants (Figures 14 and 17). This negative effect on germination is not consistent with findings of past studies or consistent across experiments, suggesting that the negative effect on germination might be due to the specific conditions under which the particular batch of vermicompost was produced. Most studies have found that vermicompost amendments in potting media either affect germination positively or do not have significant impacts on germination (Alves and Passoni, 1997; Edwards & Burrows, 1988; Bachman &

Metzger, 2008). The unusual results in our study were likely caused by an excess of ammonia in the vermicompost preparation (Table 11), possibly because it was not allowed to mature long enough. Anecdotal evidence from the Dickinson College Farm (DCF) beyond our study suggests that on-farm vermicompost-amended potting media only cause low germination rates except with lettuce (Jennifer Halpin, personal communication, April 26,

47 2012). This is attributed to the high sensitivity of lettuce to ammonium phytotoxicity, also called “jelly butt” in developed lettuce plants (Queensland Government, 1997). This often occurs in wet, cold soils and is exacerbated in high-range springtime temperatures (warm days and cool nights), both of which pertained to the conditions of Experiment 3

(Queensland Government, 1997). Thus, germination effects might have been less pronounced with other vegetable species. However, these data are still valuable because lettuce is a major crop for not only DCF, but also most small-scale diversified vegetable farms in the U.S.

Finding ways to reduce ammonia levels in the farm’s vermicompost would be valuable, in particular for increasing the effectiveness of vermicompost when growing lettuce.

Even though the vermicompost medium in Experiment 1 had a higher vermicompost concentration (33%) than in Experiment 3 (10%), the vermicompost medium in Experiment

1 contained ammoniacal nitrogen within the normal range (Table 6), whereas vermicompost media in Experiment 3 had high ammoniacal nitrogen contents (Table 11). Furthermore, there was no evidence of vermicompost toxicity in Experiment 1. This suggests that temporal inconsistencies likely exist within the vermicompost system on DCF. More rigorous management of the inputs and outputs of the on-farm vermicompost system could enhance its efficacy in future applications and promote batch-to-batch consistency. For example, pre- composting the feedstock could reduce the ammonia toxicity (Pittaway, 2001). Thermophilic composting kitchen waste for 9 days prior to vermicomposting improved vermicompost mass reduction, moisture management and pathogen reduction in a previous study (Nair et al.,

2006).

Switching from the McEnroe commercial medium to the on-farm media assessed in our study may mean sacrificing productivity to some extent in terms of germination (Figure

48 14), but in terms of transplant growth, blood meal mix-amended media performed similarly to McEnroe, and in particular, the 20% vermicompost+blood meal mix medium performed notably better (Figure 16). Thus, blood meal mix enhanced transplant growth, as was found by Leonard and Rangajaran (2007), which affirms the potential for on-farm media improvement in terms of maximizing transplant growth. With further experimentation on optimum concentrations of the various ingredients and compost maturity assurance, on-farm media can reach the level at which the trade-off between increased localized agroecological benefits and potential yield losses due to lowered germination is worth making. However, when choosing potting media inputs, enhancing the rhizosphere bacterial community is important for plant growth and health (Jack et al., 2011), so the effects of different nutrient amendments on the microbial community should be further explored.

Since peat extraction causes non-renewable habitat degradation and harmful emissions, coir is considered the more sustainable option in terms of its renewability. Our results suggest that this substitution might require sacrifices of plant productivity. However, the addition of lime to the coir media, which caused alkaline pH levels (Table 11), meant that a fair comparison could not be made between peat and coir based on our experiments.

Handreck (1993) reported that when coir was used as a direct substitute for peat, about 10 mg/l extra nitrogen needed to be added, but coir provided extra potassium. The high potassium content of the coir media found in our study is consistent with the findings of

Handreck (1993), but our coir-media also contained marginally higher nitrogen contents than the peat media. Thus, coir-based media demonstrate potential to improve and contribute to enhanced transplant growth. In practice on DCF beyond our study, on-farm coir-based

49 potting media amended with vermicompost and without lime have performed well in terms of transplant growth (Jennifer Halpin, personal communication, April 26, 2012).

Although vermicompost extracts in our study had the highest nitrate and potassium contents (Figure 13), they did not significantly improve transplant growth when applied to foliarly (Table ). This finding was consistent with results from the preliminary study of on- farm extracts (Sinchi et al., 2011). Previous studies have found that additives that stimulate microbial growth, such as kelp and humic acid or molasses, increased extract efficacy, specifically in terms of disease suppression (Carpenter-Boggs, 2005; Scheuerell & Mahaffee,

2004). Pant et al. (2009) reported that vermicompost extracts produced with and without additives both significantly increased plant growth when applied to leaves and root zones, those with additives marginally more so. We did not assess the use of microbial additives or root zone application in this study, which might account for our different results.

Alternatively, extract foliar sprays could affect crop quality more so than yield, acting not as a fertilizer, but a means of plant support (Fritz et al., 2008).

Conclusions

This series of three experiments provided useful insights into the value of farm-based vermicompost and thermophilic compost applications on Dickinson College Farm. Although vermicompost media treatments yielded low germination rates, the surviving seeds grew into more healthy and productive transplants than with other media preparations. Among on-farm media, optimal transplant growth was achieved with 20%-30% vermicompost and an addition of blood meal mix. However, it was difficult to control for differences between specific batches of vermicompost and thermophilic compost when comparing across experiments. Vermicompost and thermophilic compost could be used in potting media and

50 aqueous extract foliar sprays not as absolute fertilizers or disease suppressants, but as supportive inoculants, filling niches for nutrient availability and microbial diversity. On-farm vermicompost and its applications continues to be assessed on DCF, not only to enhance the farm’s own practices, but also to spread practical knowledge to other small-scale sustainably managed farms. Future studies should focus on microbial and nutrient content characterizations of vermicompost in various temporal and spatial batches, effects of coir- based and vermicompost-amended pH-neutral potting media on plant growth and disease suppression, and effects of microbial stimulant additives and different methods of application on vermicompost extract efficacy.

Acknowledgements

I would like to thank Jenn Halpin and Matt Steiman for their collaboration and promotion of vermicompost on the farm, Allison Jack for her invaluable insight and guidance, and Candie Wilderman and Mary Orr for their support from the Environmental

Science Department.

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