Effects of Vermicompost in Potting Soils and Extract Foliar Spray

Dickinson CollegeDickinson Scholar

Honors Theses By Year Honors Theses

5-20-2012

Effects of Vermicompost in Potting Soils andExtract Foliar Sprays on Vegetable Health andProductivityAnna Rose FarbDickinson College

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

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

1

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

2

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

3

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 Farms vermicompost bed.

4

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 worms 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 &

5

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

6

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

7

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

8

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 farms 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.

9

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).

10

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 DCFs 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 10

6 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

11

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.

12

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 colleges dining hall, whereas the

vermicompost feedstock was composed of vegetable waste from the fields. DCFs

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.

13

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

14

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.

15

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

Media

treatments

Details Aqueous extract

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,

calcinated clay, gypsum, blood meal

Control (water)

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 -



BM, 10% TC Peat base, 10% 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


Coir Coir base (70 coir: 30 vermiculite v/v, lime (3 lbs.

yd-3

)), BM mix (7 lbs./ yd3)

Control (none), VC

Coir, VC Coir base, 10% v/v VC, BM mix (7 lbs. yd-3


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

media treatment, Romaine

trial 2: 48 per media

treatment, Romaine trial

3: 40 romaine per media

treatment germinated in

cooler, Pak choi trial: 48

per media treatment

Potting soil analysis, germination (all trials),

transplant growth rate (weekly height, #

leaves, total leaf area; 1, 2), plant harvest

(height, (height, # leaves, total leaf area, root

length, root and shoot dry wt, root:shoot ratio;

1, pak choi), leaf Brix, NO3- and K

+

(preliminary), extract NO3- and K

+

Sept.-Dec.,

2011

2 32 romaine per media

treatment

Germination, transplant data (length, # leaves,

aboveground biomass, harvest index)

Feb.-March,

2012

3 90 romaine per media

treatment (n=30)

Potting soil analysis, germination, transplant

data (# leaves, length, aboveground biomass,

harvest index)

Feb.-April,

2012

16

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 Martins 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

17

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 40-60F during the night and

60-85F 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

18

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

19

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

20

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 + 10% TC

Base + 20% VC

Base + 20% TC

Base + 30% VC

Base + 30% TC

BM

mix

Base + BM mix + 10% VC

Base + BM mix + 10% TC





McEnroe

21

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 70F-heating mats in a plastic-sheeted

greenhouse ranging 40-60F during the night and 60-95F 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

22

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

23

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 70F-heating mats in a plastic-sheeted greenhouse

ranging from 40F to 95F, and were spray-irrigated daily or as needed.

24

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

25

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.

26

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

27

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

space (%)

82.5 83.2 79.2 - -

Soil porosity (%) 93.0 93.8 84.3 - -

pH 5.8 5.9 5.9 5 6

Soluble salts

(mmhos/cm)

2.39 1.25 5.00 0.7 3

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

were similar across the media treatments for each trial (22=1.1, 4.4, 3.2, 1.3, respectively,

28

P>0.1 for each). Since McEnroe commercial medium is a well-established medium with

enhanced constituents and this experiment was DCFs 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

29

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).

30

Table 7. Experiment 1 transplant growth rate and harvested plant growth (meanstandard

error).

Parameter Trial 1/3 VC 1/3 TC M

Transplant growth rate

Height (mm/day) Romaine 1*** 3.200.22 0.930.12 1.890.28

Romaine 2*** 1.830.08 1.500.12 3.760.21

Leaves (lpd) Romaine 1** 0.180.02 0.120.02 0.210.02

Romaine 2*** 0.200.01 0.170.01 0.270.01

Total leaf area

(cm2/day)

Romaine 1** 3.710.29 1.070.27 3.670.75

Romaine 2 2.880.60 2.680.50 3.460.70

Harvested plant growth

Height (mm) Romaine 1 125.749.05 159.5311.12 134.2512.92

Pak choi 134.78.52 159.86.77 160.710.23

# leaves Romaine 1 264.03 23.81.02 29.43.25

Pak choi* 141.00 16.21.43 20.671.86

Root length (mm) Romaine 1 155.655.89 142.0510.79 153.699.79

Pak choi 266.412.04 234.915.86 229.617.71

Root dw (g) Romaine 1 0.760.18 0.680.08 0.890.26

Pak choi** 0.440.05 0.560.02 0.810.12

Shoot dw (g) Romaine 1 24.2210.96 33.886.69 50.6116.21

Root:shoot ratio Romaine 1 0.060.02 0.020.00 0.040.02

Total leaf area (cm2) Romaine 1 3518.431203.16 3927.85391.49 5328.661484.72

Differences among groups: *significance at P

31

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

32

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.

Figure 13. Experiment 1 nitrate and potassium concentrations (meanstandard 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.

0

50

100

150

200

250

300

350

VC TC Control

Co

nce

ntr

ati

on

(p

pm

)

Spray treatment

NO3

K

NO3-

K+

33

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

on germination (12=18.1, P

34

Figure 14. Experiment 2 germination (meanstandard 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

35

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).

36

Figure 15. Experiment 2 number of leaves, length, aboveground biomass and harvest index

(meanstandard 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).

5

6

7

8

9

10

11

10 20 30

# l

eav

es

Compost concentration (%)

Base-VC Base-TC

BM-VC BM-TC

M

0

20

40

60

80

100

120

140

160

10 20 30

Len

gth

(m

m)


Base-VC Base-TC

BM-VC BM-TC

M

0.00

0.05

0.10

0.15

0.20

0.25

0.30

10 20 30

AG

bio

mass

(g)


Base-VC Base-TC

BM-VC BM-TC

M

0.000

0.005

0.010

0.015

0.020

0.025

10 20 30

Harv

est

ind

ex (

g/c

m)


Base-VC Base-TC

BM-VC BM-TC

M

37

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

leaves

Nutrient treatment (base, BM mix)

Compost type (VC, TC)

Compost concentration (10%, 20%, 30%)

Nutrient treatment*compost type

Nutrient treatment*compost concentration

Compost type*compost concentration

Nutrient treatment*compost type*compost concentration

197.0

23.1

7.5

5.8

3.7

4.2

6.6

1,210

1,210

1,210

1,210

1,210

1,210

1,210

38

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.

39

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.

40

Table 11. Experiment 3 physico-chemical analyses of peat- and coir-based media with and

without vermicompost.

Peat Peat,

VC

Coir Coir,

VC

Normal range

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

space (%)

10.5 11.3 20.2 20.7 - -

Soil porosity (%) 96.3 95.8 97.0 95.9 - -

pH 6.3 6.9 8.0 7.5 5 6

Soluble salts

(mmhos/cm)

0.37 1.40 0.96 1.40 0.7 3

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.

41

Figure 17. Experiment 3 germination (meanstandard 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

42

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).

43

Figure 18. Experiment 3 number of leaves, length, aboveground biomass and harvest index

(meanstandard error) of peat-based and coir-based media with 0% vermicompost (control)

and 10% vermicompost.

2

3

4

5

6

7

8

9

0 10

# l

eav

es

VC concentration (%)

Peat

Coir

0

10

20

30

40

50

60

70

80

90

100

0 10

Len

gth

(m

m)


Peat

Coir

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0 10

AG

bio

mass

(g)


Peat

Coir

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0 10

Harv

est

ind

ex (

g/c

m)


Peat

Coir

44

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

leaves

Base (peat, coir)

VC concentration (0%, 10%)

Extract treatment (no, yes)

Base*VC concentration

Base*extract treatment

VC concentration*extract treatment

Base*VC concentration*extract treatment

122.9

68.0

0.3

23.8

1.4

0.0

0.0

1,60

1,60

1,2

1,60

1,60

1,60

1,60

45

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

46

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).

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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,

48

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 farms 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

49

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

50

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

51

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

farms 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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