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Published online 7 November 2005
Published in J Environ Qual 34:2310-2317 (2005)
DOI: 10.2134/jeq2004.0332
© 2005 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America
677 S. Segoe Rd., Madison, WI 53711 USA
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TECHNICAL REPORTS

Waste Management

Assessment of Wool Waste and Hair Waste as Soil Amendment and Nutrient Source

Valtcho D. Zheljazkov*

Department of Plant and Animal Sciences, Nova Scotia Agricultural College, 50 Pictou Road, Cox Institute R-151, P.O. Box 550, Truro, Nova Scotia, Canada B2N 5E3

* Corresponding author (vjeliazkov{at}nsac.ca)

Received for publication August 25, 2004.

   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIAL AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
A field and two container experiments were conducted to assess uncomposted wool and hair wastes as a nutrient source for crops and to evaluate their potential to improve soil biological and chemical properties. Overall, addition of wool or hair waste to soil increased yields of basil (Ocimum basilicum L. ‘Trakia’), thorn apple (Datura innoxia Mill. ‘Inka’), peppermint (Mentha x piperita L. ‘Black Mitchum’), and garden sage (Salvia officinalis L. ‘Desislava’), increased NH4–N and NO3–N in soil, increased total N (and protein) content in plant tissue, stimulated soil microbial biomass, and decreased mycorrhizae colonization of plant roots of thorn apple but not in basil. Wool and hair waste additions to soil altered slightly the content and composition of plant secondary metabolites (essential oils or alkaloids); however, overall the constituents remained within the "typical" range for the respective crops. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis demonstrated that wool and hair wastes decompose slowly under field or greenhouse conditions, and act as a slow release S, N, P, and K fertilizer. These results, along with the measured concentrations of NO3–N in soil at harvest, suggest that the addition of wool or hair waste of only 3.3 g kg–1 of soil may support two to five harvests or crops under greenhouse conditions and two to four field seasons in field production systems, and would improve soil biological and chemical characteristics. Further research is needed to optimize the rate of application of these waste materials to the nutrient requirements of specific crops to avoid nitrate leaching into the ground water. In addition, the effect of wool and hair waste on other environmental end points should also be further investigated before specific recommendations for growers are provided.

Abbreviations: ANR, apparent nitrogen recovery • BSE, backscattered secondary electron • EDX, energy dispersive X-ray • MSW, municipal solid waste • % RLM, percent root length colonized by mycorrhizae • SEM, scanning electron microscopy


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIAL AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
THE ECONOMIC and environmental sustainability of agricultural systems depends on the careful selection of inputs such as inorganic and organic fertilizers. A number of "waste materials" such as biosolids (sewage sludge), municipal solid waste (MSW) compost, animal manures, and other composted and raw organics have been traditionally used as a nutrient source for agricultural crops and/or as soil conditioners. While there is a significant body of research available on the above organic nutrient sources, there has been limited research on the use of other organic wastes, such as wool waste and human hair waste, as soil amendments and nutrient sources for agricultural crops.

Sheep production and wool processing generates a significant amount of waste materials such as woolscour sludge (Williamson et al., 2000; Duppong et al., 2004; Kroening et al., 2004) and other unused materials that must be landfilled. In recent years, the market for wool in Atlantic Canada has dropped dramatically resulting, in addition to the wool waste, an excess of good quality wool that cannot be processed. According to the Nova Scotia Wool Board and Nova Scotia Pure Breed Sheep Association, it is estimated that more than 30000 kg of wool is stored in Nova Scotia alone. The excess and waste wool are currently being landfilled or discarded in the woods and possibly creating environmental problems. There are significant economic losses for sheep producers, since it costs approximately 66 cents kg–1 of wool to shear a sheep. Wool in Atlantic Canada is no longer a commercially viable product; therefore, an alternative use for this protein-rich product and by-product needs to be identified.

Barbershops generate a significant amount of human hair waste that is usually put in the garbage and ultimately ends up in landfills. Due to the high N content of wool and hair wastes, dumping these wastes in wooded areas or landfilling increases the probability of nitrates leaching into the ground water. A preliminary study indicated that hair and wool wastes have similar elemental composition and are high in N (Table 1). However, no report is available on the use of hair waste as a nutrient source for plants or as a soil conditioner. The hypothesis that prompted this study is that wool and hair wastes that are currently landfilled can be utilized as a nutrient source and potting substrate for greenhouse or field production of high value crops, or as a soil conditioner.


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  		Table 1. Selected properties of human hair wastes and sheep wool wastes.{dagger}

 
There are few reports on the use of wool as a feedstock for composting (Plat et al., 1984; Verville, 1996; Das et al., 1997), as a mulch for weed control (Hartley et al., 1996; Hartley and Rahman, 1997), and on the use of composted wool as a nitrogen source for plants (Tiwari et al., 1989a, 1989b). However, composting results in loss of nutrients, especially N (Epstein, 1997). Furthermore, composting of alternative substrates is usually conducted to reduce the risk of phytotoxicity and to lower the C to N ratio (Epstein, 1997). In a field experiment, Kumar and Awathi (1977) reported that the addition of 0.2 Mg of cotton waste and 0.22 Mg ha–1 of wool waste increased grain sorghum yields. Hartley et al. (1996) found that wool dust used for weed control in apple orchards changed the number of earthworms, pH, and soil temperature.

There is no comprehensive study in the literature on the possible use of uncomposted waste wool or hair waste as potting medium or soil amendment for agricultural crops. The purpose of this study was to assess uncomposted wool and hair waste as nutrient source for crops and to evaluate their potential to improve soil biological and chemical properties. Wool or hair waste may prove to be a useful resource as an inexpensive alternative to commercial sources of N, S, K, and possibly other nutrients. The objective was met by conducting two container and one small-plot field experiments. Basil, thorn apple, peppermint, and garden sage were used as representative plant species for high-value aromatic and medicinal crops. Basil and peppermint are commercially grown as greenhouse culinary crops, for herbal teas, or as field crops for the commercial production of essential oils (Mustjatse, 1985; Hay and Waterman, 1993). Thorn apple is an alkaloid containing plant that has been grown either as a field or a greenhouse crop (Dzhurmanski, 1980; Atal and Kapur, 1977). Garden sage is a perennial crop grown for the commercial production of essential oil or dried leaves for culinary use or herbal teas (Kintzios and Kintzios, 2000). The above species represent a good cross-section of aromatic and medicinal plants since they are either annual, biannual, or perennial species, and all are high-value crops. Basil, peppermint, and garden sage are established herbs and ornamentals in Atlantic Canada. There is ongoing research at the Nova Scotia Agricultural College targeting further development of these four species for the commercial production of essential oil (basil, peppermint, and garden sage) or alkaloids (thorn apple).


   MATERIAL AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIAL AND METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS
 REFERENCES
 
Waste Material
Human hair waste was collected from two local barbershops by sampling 2 to 4 kg biweekly over a 4-mo period and represents a mixture of hair from people of different gender and age. Wool waste was sampled from the Nova Scotia Agricultural College sheep barn and represents unprocessed and unwashed wool from Texel and Rideau Arcott ewes (ranging from yearlings to 10 yr old), collected over a 2-yr period. The ewes were kept in an open fronted barn, bedded with straw and hay during the winter. The ewes were shorn in May and the wool was stored in burlap bags for up to 2 yr. Both hair and wool waste were carefully mixed to generate representative subsamples that were later used in the container and field studies.

Container Experiments
Both experiments were conducted in the greenhouse at the Nova Scotia Agricultural College. Treatments in the first container experiment consisted of 0, 40, 80, and 120 g of waste wool addition to 6 kg of soil, whereas treatments in the second container experiment consisted of 0, 20, 40, and 80 g of human hair waste per 6 kg of soil. Both experiments had a second control with the same treatments but with no plants to evaluate the effect of plants on nutrient availability. Basil and thorn apple were used in the first, whereas peppermint was used in the second container experiment. Loading rates were adjusted only for the second experiment based on preliminary experiments indicating lack of crop yield increase with the addition of 120 g of hair or wool waste to soil.

Plants in both experiments were grown in 30-cm plastic containers filled with 6 kg of soil, using a randomized block design in four replicates. Plastic trays were placed under each container to avoid nutrient leaching. Basil and thorn apple plants were started as seeds, whereas peppermint plants were started from rhizomes. After emergence, plant numbers were reduced to two per container. Plants were grown for 14 wk with a 14-h day and 10-h night photoperiod, with an average day temperature of 28°C. Plants were irrigated carefully and evenly once a day with sufficient water to the point of flow to provide the necessary moisture while avoiding filling of the trays under the containers. The plant species were harvested at the same time, when all plants were flowering (which is the technical maturity for basil, peppermint, and sage), by cutting the stems about 4 cm above the soil surface. Peppermint and sage plants were distilled fresh, immediately after the harvest, and half of the herbage from basil and thorn apple was air-dried for secondary metabolites analysis. The remaining half from each species was dried at 70°C for 72 h for mineral and trace elements analysis.

Preliminary experiments demonstrated that plants may not grow well in containers with Truro loamy soil and wool waste unless a chemical fertilizer or compost is added, probably because wool and hair are keratinaceous materials and very resistant to degradation (Ignatova et al., 1999). Hence, 300 g of air-dried MSW compost was added to each container in the first experiment with wool waste. The MSW compost had a 618 g kg–1 moisture content, 83 g kg–1 C, 12.4 g kg–1 N, 6.7 C to N ratio, 7.2 pH (H2O), and 2.4 dS m–1 electrical conductivity (EC) on a wet weight basis. The elemental composition of compost was established following nitric acid digestion (Zheljazkov and Warman, 2002) and was as follows: Ca 12.3 g kg–1, P 3.3 g kg–1, Na 2.24 g kg–1, K 4.72 g kg–1, Mg 2.13 g kg–1, Fe 3207 mg kg–1, Mn 484 mg kg–1, Zn 90.8 mg kg–1, B 14.5 mg kg–1, and Cu 11 mg kg–1. The MSW compost met the Canadian compost quality guidelines (Bureau de normalisation du Quebec, 1997).

Field Experiment
Garden sage was used in the field experiment. Sixty-day-old seedlings were transplanted to the field on 10 June 2001 and grown for four seasons. The treatments in the field experiment consisted of 0, 15.8, and 31.7 Mg ha–1 of wool waste. The wool waste was applied on 15 Oct. 2001, in open furrows between the rows of garden sage, and covered with 12 to 15 cm of soil to minimize N losses. Sage plants were harvested twice in 2002 and twice in 2003 (in July and October, respectively) by cutting green shoots with fully developed leaves and inflorescences above the level of woody branches.

Nutrient, Trace Elements, Microbial Biomass, and Mycorrhizae Analysis
Immediately after the harvest, half of the herbage from basil, thorn apple, and garden sage was oven-dried at 70°C for 72 h, the dry weight was recorded, and the herbage was ground using a Wiley mill to pass through a 1.0-mm screen. Fresh soil samples from all experiments were taken at harvest and kept in a cooler at 4°C for microbial biomass and nitrate N and ammonium N analysis. Additional soil samples for nutrient and trace element analysis were taken at harvest, air-dried (at 20°C), and ground with a mortar and pestle to pass through a 2.0-mm screen.

For tissue and soil nutrient and trace element analysis, plant tissue and air-dry soil samples were decomposed in concentrated nitric acid (Zheljazkov and Warman, 2002). Also, air-dry soil samples were extracted with Mehlich 3 extractant (Mehlich, 1984). The samples were analyzed for nitric acid–extractable (total) and for Mehlich 3–extractable (plant available) concentrations of Cu, Mn, Zn, Ca, Fe, K, Mg, P, S, B, Cd, Co, Cr, Mo, Na, and Ni by an inductively coupled argon plasma spectrometer (ICAP) (Model 61; Thermo Jarrell Ash, Franklin, MA). Extraction of NO3–N and NH4–N was conducted with 2.0 M KCl (Bremmer, 1965; Sanderson and MacLeod, 1994). Fresh soil samples (10 g) were weighed for wet bulk density, extracted in 50 mL of 2 M KCl by shaking for 1 h, and subsequently vacuum-filtered through Whatman (Maidstone, UK) 934AH paper. The NO3–N and NH4–N were measured on a TRAACS 800 AutoAnalyzer (Technicon Industrial Systems, Tarrytown, NY).

Soil microbial biomass was measured as an indicator for potential toxicity of added wool waste to soil, using the chloroform fumigation–incubation procedure (Jenkinson and Powlson, 1976). Briefly, 25 g of oven-dried weight equivalent fresh soil samples were fumigated with boiling chloroform in a desiccator at 40°C and incubated in the dark for 24 h at 25°C. Moisture of the incubated and the nonfumigated control soil was readjusted, 1.25 g of fresh soil was added to each sample, and samples were sealed and incubated for a week. The CO2 in each bottle was measured by gas chromatography. The microbial biomass C was calculated as:

[1]
where 0.45 is a constant relevant to acidic soils and CO2–C = µg CO2–C per gram oven-dried weight equivalent of soil. The biomass C was given as mg of microbial C per g of soil.

Mycorrhizae analyses were conducted to determine the effects of hair and wool waste additions to soil on mycorrhizae. The root systems of plants were excavated and washed, and the fine secondary roots were removed and preserved in 50% ethanol. The root samples were heated for 30 min at 90°C in 10% KOH, rinsed, acidified in 1% HCl for 5 min, stained with 0.01% acid fuchsin–lactic acid for 15 min at 90°C, and destained in lactic acid (Kormanik et al., 1980; Kormanik and McGraw, 1982). Percentage root length colonized by mycorrhizae was assessed using the grid line intersection method under a scope (Giovanetti and Mosse, 1980).

Extraction and Analysis of Essential Oils and Alkaloids
Fresh peppermint and sage as well as air-dried basil samples (100 g) were steam distillated (120 minutes) to extract the essential oils using a modified Clevenger apparatus (Furnis et al., 1989, p. 171–175). The alkaloids of thorn apple were extracted as indicated in Herouart et al. (1991), using 20 g of dry tissue and ethanol extraction. The essential oils and alkaloid samples were analyzed by gas chromatography (GC) with a PerkinElmer (Wellesley, MA) TurboMass with both mass spectrum (MS) and flame ionization detection (FID) using a Supelco (Bellefonte, PA) MDN-55 capillary column at the following program: initial temperature of 75°C, held for 4 min, followed by 4°C min–1 increase with a total run time of 35 min to final temperature of 199°C. The injection volume was 1.0 µL and the injector temperature was 240°C. The helium carrier gas flow rate was 1.0 mL min–1 for GC–MS and 2.0 mL min–1 for FID analysis and standards were used for comparison of retention times.

Scanning Electron Microscopy and Energy Dispersive X-Ray Analysis
Scanning electron microscopy (SEM) and X-ray microanalyses were used to assess the extent of wool and hair waste degradation with time, and visualize the spatial distribution of nutrients at and around the waste materials. Samples were observed in a Hitachi (Tokyo, Japan) 3000N variable pressure SEM coupled to an Oxford Instruments (Concord, MA) INCA 350 energy dispersive X-ray (EDX) spectrometer. The SEM images of soil, wool, and hair were taken using a backscattered secondary electron detector (BSED) or environmentally secondary electron detector (ESED). Low vacuum in the specimen chamber and a Peltier cooling stage (to maintain –15°C at the specimen stage) were utilized to observe the samples in their natural state. The EDX analysis was performed on unpolished samples at a working distance of 15 mm, using accelerating voltages of 10 to 30 kV, and pressure in the specimen chamber of 5 to 50 Pa, depending on sample charging.

Data analysis of all data sets was performed using two-way ANOVA with SAS (SAS Institute, 2000); where the interactions or main effects were significant, separation of means was conducted.


   RESULTS AND DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIAL AND METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS
 REFERENCES
 
Soil and Waste Analysis
The soil used in the container experiments was a poorly drained coarse loamy Truro soil, while the soil in the field experiment was well-drained loamy Truro soil (Table 2). Both soils are representative of agricultural soils in Atlantic Canada and had unequal amounts of sand, silt, clay, and some nutrients. Human hair waste contained more N, S, Ca, C, and Cu than the wool waste, while wool waste contained much more K, Na, Fe, and P than waste hair (Table 1). Initial analysis suggested that sheep wool waste may be a more balanced organic fertilizer for plants than hair waste, but wool waste would also introduce a significant amount of Na into the growing medium.


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  		Table 2. Initial soil characteristics (0–15 cm) of soils used in the container and in the field experiments.

 
Wool and Hair Waste Container Experiments
Addition of wool or hair waste to soil increased soil NH4–N and NO3–N, basil, thorn apple and peppermint yields, and N uptake relative to the unamended control (Table 3). The apparent nitrogen recovery (ANR) from wool with basil and thorn apple was 1.04 to 8.2%, whereas ANR from hair waste ranged from 13 to 32% with peppermint (data not shown).


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  		Table 3. Plant yields, total N, NH4–N, NO3–N content in soil, and total N in plant tissue of basil, thorn apple, and peppermint grown in pots with addition of wool or hair.

 
The results on NH4–N and NO3–N in soil suggest that (i) most of the NO3–N in soil is due to mineralization of N in wool or hair rather than mineralization of soil N, (ii) the presence of plants may not significantly affect wool or hair degradation (Tables 3 and 5), and (iii) the addition of 40 g wool or hair waste to 6 kg of soil would support two to three harvests or crops. Also, addition of wool or hair increased total N (and protein) content in tissue (Tables 3 and 5), which may be important for crops such as peppermint and basil that are distilled for essential oil and the byproduct is subsequently used as animal feed (Djouvinov et al., 1997).

Total crude alkaloid content of thorn apple depended mainly on the total fresh yields, and was higher in the 120 g pot–1 treatment, lower in the 40 and 80 g treatments, and lowest in the unamended control (Table 3). Three main alkaloids were identified: aposcopolamine (in the largest concentration), hyoscyamine, and scopolamine (in lower concentration). Increasing the amount of wool waste addition to soil tended to increase the ratio of aposcopolamine to scopolamine. However, there was significant variation in alkaloid content between the replicates within a treatment.

Wool waste addition to soil significantly increased basil essential oil content and yield (Table 3), probably due to N and S from the wool waste. Nitrate N can increase basil oil content and yields (Takano and Yamamoto, 1996) and composition (Adler et al., 1989). Also, S is known to increase basil oil content (Suh and Park, 1999). Linalool, eugenol, 1,8-cineole, {alpha}-terpineol, borneol, cadine, and {alpha}-humulene were identified as major oil constituents of basil oil. Treatments altered basil essential oil composition (data not shown); however, the overall oil composition remained within the "typical" basil oil composition (Bowes and Zheljazkov, 2004).

Peppermint oil content (Table 3) was not altered by hair waste addition and was quite high relative to other reports indicating 3 to 4 g kg–1 oil content of fresh peppermint (Mustjatse, 1985; Topalov and Zheljazkov, 1991). However, the addition of hair did increase peppermint oil yields due to the increased biomass. Several oil constituents were identified in peppermint oil: limonene, eucalyptol, menthone, menthofuran, neomenthol, menthol, {alpha}-terpineol, pulegone, menthyl acetate, and ß-caryophyllene. Treatments altered peppermint essential oil composition (data not shown), but the overall composition remained within the normal range for peppermint oil (Mustjatse, 1985; Stengele and Stahl-Biskup, 1993). Generally, hair waste addition to soil increased the concentration of menthol and reduced the concentration of menthyl acetate in peppermint oil.

Microbial biomass and percentage root length colonized by vesicular arbuscular mycorrhizae (% RLM) were measured as an indication for potential toxicity of waste wool on soil microorganisms. Addition of wool waste to soil decreased % RLM in thorn apple (Table 4) but not in basil (data not shown), whereas addition of 20 and 40 g of hair waste to soil increased % RLM in peppermint (Table 4). These results demonstrate differential response to treatments depending on the plant species. Also, results from this study support the understanding that vesicular arbuscular mycorrhizae need sufficient N in the soil to develop extensive mycelium (Hawkins and George, 1999); however, high fertility levels may suppress mycorrhizae in some crops. It has been reported that addition of N may either increase or decrease root colonization by mycorrhizal fungi (Corkidi et al., 2002). Results from this study demonstrated a directly proportional relationship between wool waste addition and soil microbes (Table 4), most probably due to the increased concentration of N in the soil. In general, N addition may stimulate microbial biomass in soil (Johnson et al., 1999); however, depending on other factors, N addition could decrease it (Johnson et al., 1999; Chen et al., 2002). Overall, the addition of wool waste to soil increased microbial biomass in containers with plants (basil and thorn apple), but not in containers without plants. One exception was the 40-g wool treatment in basil, where due to the large variation no significant increase of microbial biomass was found relative to the control (Table 4). Results suggest that the presence of basil and thorn apple plants stimulates microbial biomass growth, probably due to the root exudates that stimulate symbiotic microbes (Dakora and Phillips, 2002). Differences in observed increase in microbial biomass between basil and thorn apple might be due to dissimilar composition of the root exudates of these two species.


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  		Table 4. Microbial biomass of soil amended with wool (0, 40, 80, and 120 g pot–1) and with no plants, or with either basil or thorn apple and percent root length colonized by mycorrhizae (RLM) of thorn apple and peppermint in container experiments.

 
Overall, wool or hair waste addition to soil affected the phytoavailability of some nutrients other than N. For instance, addition of wool waste to soil increased phytoavailable (Mehlich 3–extractable) and soil total (HNO3–extractable) concentrations of S and Na in containers with plants (data not shown). Also, wool waste addition to soil increased tissue P, K, Ca, S, Mn, Zn, and Na in basil, and increased tissue S and Mn but decreased tissue Mg and Na in thorn apple. These results suggest that either (i) Mehlich 3 extraction may not predict very well tissue nutrient concentration in plants, or (ii) different plant species respond differently to the same concentrations of nutrients in soil. The latter phenomena may be due to the dilution effect, since thorn apple responded more strongly to increased rates of wool waste addition to soil than basil (Table 3). Due to increased thorn apple yields, tissue Mg and Na decreased, but the actual Mg and Na uptake did increase with increasing rates of wool waste addition (data not shown). Hence, in some instances Mehlich 3 may predict overall nutrient uptake but not tissue concentration of the same nutrient.

Since industrial compost can increase heavy metals and trace elements in the plant tissue (Deportes et al., 1995; Epstein, 1997), and since MSW compost was added to all pots, heavy metals and trace elements in plant tissue were measured. Tissue Mn, Zn, and Cu in this study was within the normal concentration of these elements in plants (Kabata-Pendias and Pendias, 1991), and there were no detectable concentrations of Pb, Cd, Cr, and Ni. Results from this and other studies (Zheljazkov and Warman, 2004) suggest that MSW compost that meets Canadian guidelines (Bureau de normalisation du Quebec, 1997) for heavy metal content in composts may be safely used as a soil amendment for agricultural crops.

Field Wool Waste Experiment
A single wool waste addition to soil in 2001 at rates of 15.8 and 31.7 Mg ha–1 also significantly increased sage herbage yields in 2002 and 2003 as well as tissue N and N uptake by the crop (Table 5). The ANR with the sage harvestable parts was relatively low, since garden sage is a perennial crop and only a small part of the aboveground herbage is harvested. In both seasons and the four harvests, essential oil content of sage in the wool waste–treated plots was lower than in the unamended plots (Table 5). However, due to the greater herbage yields, overall essential oil yields were higher in the wool waste–treated plots. Treatments altered sage essential oil composition (data not shown).


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  		Table 5. Plant yields (average 2002 and 2003), tissue N, N uptake, and apparent N recovery with yield from the field experiment with sage amended with 19 and 38.6 Mg ha–1 of waste wool.

 
Scanning Electron Microscopy and Energy Dispersive X-Ray Analysis
The SEM analysis of the wool waste and soil sampled from the field experiment in the spring of 2004 and 2005 demonstrated that some wool fibers appeared well preserved (Fig. 1) while other fibers were significantly decomposed. The EDX microanalysis of the same samples indicated the presence of C, O, S, and N (Fig. 2) and some P and K on the surface. X-ray mapping of a decomposing wool fiber indicated a strong S signal, but much lower counts of N, P, or K compared to fresh wool (data not shown). Since samples were observed in their natural state and without polishing, results should be treated with caution and should be considered semiquantitative. Still, the SEM–EDX analyses demonstrated that wool waste added to soil under field conditions (in the cool wet climate of Atlantic Canada) would decompose and slowly release nutrients over three to four field seasons like a slow release fertilizer. Soil and hair samples were taken from the hair waste container experiment for SEM–EDX analyses 22 and 33 mo after emergence. The first peppermint cut was taken at 14 wk after emergence, but the crop was grown for 35 mo to assess the degree of hair waste degradation over time. Results show that after 33 mo in the soil and supporting five harvests of peppermint, some of the hairs retained the original microstructure in some areas (Fig. 3–6) . The EDX analyses demonstrated that decomposing and fresh hair surfaces contained similar amount of C, O, and S, but decomposing hair had less N than fresh hair. Hence, the addition of 20 to 80 g of hair waste to 6 kg of soil may meet the N, P, K, and S requirements of peppermint for at least 22 mo and support up to five harvests as a slow release fertilizer. The SEM microstructural analyses indicated no differences among treatments with respect to number of essential oil glands per area, diameter of the glands, number of trichomes, or other microstructural alterations. Essential oil glands covered the entire leaf, including the mid-vein, an observation that has not been previously reported.



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  		Fig. 1. Backscattered electron (BSE) scanning electron microscope (SEM) image of decomposing wool waste fiber from the sage field experiment at a magnification of 1000x. This image also illustrates the site on the wool fiber where the EDX microanalysis was performed. The wool was applied to the sage field experiment in October 2001, and the sample shown was taken in April of 2005.

 


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  		Fig. 2. Scanning electron microscope (SEM) and energy dispersive X-ray (EDX) microanalysis of decomposing wool fiber. This is a spectrum of the site on degrading wool fiber from the sage field experiment, sampled in April of 2005, as shown in Fig. 1.

 


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  		Fig. 3. Backscattered electron (BSE) image in the compositional mode at 20.0-kV accelerating voltage and at a magnification of 500x of decomposing hair (strand in the middle of the image) and fresh hair (strands on both sides of the decomposing hair strand). The decomposing hair samples are from the 80-g hair waste treatment in the peppermint container experiment.

 


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  		Fig. 6. Energy dispersive X-ray (EDX) analysis of decomposing hair. This is a spectrum at the site of interest on the decomposing hair sample, as shown in Fig. 5.

 


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  		Fig. 4. Scanning electron microscope (SEM) and energy dispersive X-ray (EDX) microanalysis of decomposing hair (strand in the middle of the image) and fresh hair (strands on both sides of the decomposing hair strand) as shown in Fig. 3. X-ray dot mapping displays P in red, K in green, and N in blue.

 


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  		Fig. 5. Backscattered electron (BSE) image in the compositional mode at 20.0-kV accelerating voltage and at a magnification of 500x of decomposing hair samples taken in April of 2005 from the 80-g hair waste treatment in the peppermint container experiment. The image also portrays a site of interest for EDX microanalysis.

 

   CONCLUSIONS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIAL AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
REFERENCES
 
Results from this study suggest that wool and hair waste may be excellent soil amendments and nutrient sources for high value crops for both greenhouse and field production systems. Although the results indicate slow degradation of wool waste under field conditions, leaching of nitrates following a single wool waste application in field production systems might be an issue. Hence, biannual and lower application rates should be tested for various perennial or annual crops, to synchronize N availability to crop N requirements and to achieve high N use efficiency (Loecke et al., 2004). Also, the effect of wool and hair waste on other environmental end points should be further investigated before specific recommendations for growers are provided. The use of a large quantity of human hair waste as a nutrient source for crops used for direct human consumption (e.g., vegetables) may be questioned; there might be issues with marketability and social acceptance. That was the rationale in this study for using crops that are grown for production of secondary metabolites (essential oils and alkaloids) and not crops that are used directly for human consumption. Also, basil and garden sage are widely used as ornamentals, and in these systems the use of wool and hair waste might be less of an issue with regard to social acceptance or marketability. Perhaps specific guidelines and regulations (such as for sewage sludge or industrial composts) should be developed for the use of these waste materials in agricultural crops. The present study is an attempt to characterize two unusual waste products (wool waste and hair waste) and demonstrated that these can be used directly as slow release plant nutrient sources without composting.


   ACKNOWLEDGMENTS
 
I acknowledge the funding support of the Nova Scotia Department of Agriculture and Fisheries, Technology Development program (Project DEV21-063). This project was also partially funded by the Nova Scotia AgriFutures Project #190, by the Purebred Sheep Association of Nova Scotia, and by the Nova Scotia Wool Marketing Board. I thank Mr. Gary Wallace, Mr. Jonathan Wort, and Mrs. Delia Burge for their support and encouragement. I thank Dr. A. Margina from the Research Institute for Roses and Aromatic Plants in Bulgaria for providing certified seeds. I also thank Mr. Scott Veitch, Ms. Lindsay Hainstock, Mr. Cory Murphy, Mr. Paul McNeil, and Ms. Stephanie Butler for their assistance. I thank Dr. Nancy Crowe and Dr. Norman Goodyear from the Nova Scotia Agricultural College for critically reading the manuscript and suggesting many improvements.


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 ABSTRACT
 INTRODUCTION
 MATERIAL AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS
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