Potential use of waste wool in agriculture: An overview

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Total world wool production and its prices in the last
two decades have been steadily declining since
1990. As per the recent figures world wool production is
1161 million kg (IWTO, 2015) and accounts for 3.51% of
total fibre production (33 million tonnes). In the recent
past, wool price in the country has also declined. As a
result, many farmers are shifting from wool to mutton in
sheep farming. Very coarse wool because of no utility in
textiles and also in other sectors ends up by burning or
burying it. Coarse wool has become an underrated and
underused resource. Belly wool, even from fine-wool
sheep, goes unsold and often referred to as 'waste
wool'. It accounts for about 20% of the total wool from a
sheep; and represents a fair amount of wool that does
not generate return to producers (Hargreaves, 2017).
Thus, waste and tag wool account a huge amount of
wool that is a readily available, inexpensive and
considered low-quality because of contamination and
stains. Further, nearly 10 to 15% of waste wool
produced in woollen industries during wool processes
(carding, combing, spinning, wad weaving, etc) is
usually discarded or dumped on the ground (Kadam et
al., 2014). These wool wastes are voluminous, light
weig ht and ri ch in pro tein an d cause seri ous
environmental hazards and air pollution. Floating of the
fine wool particles from waste wool in air causes severe
allergic rhinitis in humans (Wang, 2005). To overcome
these problems, there is need to have efficient
environment friendly wool waste disposal system. It can
be decomposed with other agriculture by-products and
used in agriculture as manure.
Recycling technologies are one of the options for
best use of waste products and materials, but not
much efforts are being made for use of waste wool
fibre (Bartl et al., 2005). There is a need to identify an
alternative use for waste wool, which is rich in protein
(Zheljazkov, 2005). The use of wool-waste from both
industries and post-consumers would reduce waste
and improve resources conservation (Watson 2005;
Miraftab and Lickfold, 2008).
POTENTIAL USE OF WASTE WOOL IN AGRICULTURE: AN OVERVIEW
S.C. Sharma*, A. Sahoo and Roop Chand
ICAR-Central Sheep and Wool Research Institute, Avikanagar- 304 501 Rajasthan
*E-mail address: drscs63@gmail.com
Manuscript received on 01.09.2018, accepted on 17.12.2018
DOI: 10.5958/0973-9718.2019.00019.9
ABSTRACT
The review aims to compile the information on recycling of wool wastes in agriculture and to
explore future research areas. Wool is a biodegradable fibre and readily recycled with significant
benefits accruing from returning to the earth as a nitrogen and sulphur-rich fertilizer. Wool-waste
produced in many forms beside shearing waste, carpet disposal, textile industries, wool scour sludge
and very coarse wool that cannot be processed. These wool wastes are included in the present
evaluation with relevant literature and focussed on applications and potential benefits of wool-waste
as a soil amendment and to identify areas where there is insufficient knowledge to implement its
usage. Along with growing public concern for theenvironment andcosts of landfillin recent years,it is
utmost urgent to look for alternative uses for inevitable wool-waste. Therefore, closed cycle
processes without significantly producing waste are being developed for many products and
materials, but rarely for fibre products. Recycling technologies are becoming increasingly important
and thereis clear needto identify an alternativeuse for this protein-rich product and itsby-products.
Key words: Agriculture, Moisture conservation, Organic mulch, Slow release fertiliser, Soil amendment, Waste wool
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2Indian Journal of Small Ruminants 2019, 25(1): 1-12
Animal manure and raw organic materials have been
traditionally used as a nutrient source for conditioning of
soil in agriculture. Organic fertilizers contain a lot of
organic nitrogen (N), but it is not mineralized fast enough
to meet the needs of the plants during critical periods
(Pang and Letey, 2000). Bioconversion has a significant
potential for transforming wool-waste into high-value
products like manures for organic farming. The concept
of 'geo-textile' for waste-wool came from the use of jute
for non-woven geo-textiles for soil stabilization and
controlling soil erosion in dry, irrigated and rain-fed
areas. These fibres can also be used in drainage-bonds
and agricultural mulching in Rajasthan. It has been
observed that wool waste of woollen mills from Bikaner
is traditionally being used by the farmers of Sikar district
since ages for improving the crop production. ICAR-
Central Sheep and Wool Research Institute, Avikanagar
(CSWRI), Rajasthan has initiated research on utilisation
of non-profitable / non-utilised coarse wool or waste
wool in agriculture for widening its use and increasing its
economic value besides reducing pollution and adding
profit to farmers from sheep rearing. There is limited
number of studies investigating the incorporation of
shredded carpet waste directly into soil in the country.
The aim of this paper is to present the current
management options for utilization of raw wool waste
and to review the research on solutions for converting
wool waste into useful organic manure for use in
agriculture.
A. Physico-chemical properties of wool
Wool is stable through alpha-keratin peptide
linkages and a highly cross-linked network of disulfide
bonds. Greasy raw wool is composed of protein 'keratin'
with an abundance of carbon (C 50%), nitrogen (N 16-
17%) and sulphur (S 3-4%), which play an essential role
in plant nutrition (Von Bergen et al., 1963). Wool is not
easily degraded in nature and causes serious pollution.
Alpha keratin, also known as hard-keratin has higher
cysteine content (up to 14%) to form S–S bonds
between cross-linking protein chains, contributing ability
to resist common proteolytic enzymes such as pepsin,
trypsin or papain (Onifade et al., 1998). In addition, the
hydrophobic groups of spiral coil in wool make it more
difficult for biodegradation (Kornillowicz-Kowalska and
Bohacz, 2011). The chemical composition and element
analysis of wool waste are presented in Table 1. The
waste wool production in promising wool producing
countries is given in Table 2 and relative contribution of
countries in total wool waste production is depicted in
Fig.1.
S.C. Sharma et al.
Table 1. Elemental concentration of wool waste
Wool waste N (%) P (%) K(%) S (%) Zn (ppm) Cu (ppm) Mn (ppm) Fe(ppm) References
Scoured wool and dust 15.78 0.01 0.005 3.21 115.00 25.00 25.00 50.00 Burn et al. (1964)
Un-composted wool and 0.11 0.08 3.30 5.13 501.00 8.00 21.00 234.00 Zheljazkov (2005)
hair waste
Shearing waste - 0.01 - 0.06- 1.87 - 73.60 - 5.30 - 3.37 - 22.03 - Patkowsa-Sokola
0.03 0.08 2.20 88.80 10.30 22.93 513.17 et al. (2009)
Machine waste 0.11 0.012 0.02 3.21 230.00 8.54 8.00 12.47 Sharma et al.
(2014)
Waste wool 2.37 0.0003 0.76 2.17 94.25 13.39 45.93 914.96 Chaudhary et al.
(2018)
Shearing waste 11.80 0.01 - 0.02 - 2.60 - 130.00 - 20.00 - 23.00 - 60.00 - CSWRI (2018)
-12.50 0.02 0.03 3.00 145.00 25.00 28.00 90.00
Table 2. Estimated waste-wool production (tonnes) in promising countries*
Country Estimated wool waste Country Estimated wool waste
Australia 119623 Turkey 18599
China 58982 Iran 14248
USA 37668 UK 12406
New Zealand 25614 India 7946
Argentina 22224
*- Estimated value on the basis of total wool production, considering 10 to 15% waste in sorting, scouring and cleaning and 12
to15% waste during wool processing

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Use of waste wool in agriculture
B. Biodegradation and composting of wool
Wool is quite resistant to the attack of micro-
organisms; only under hydrophilic conditions they are
able to breakdown the keratinous fibre. It takes months
to degrade the wool. The functional groups of wool
start to degrade and convert into biomass after 4
weeks and weight loss up to 33% was reported under
hydrophilic conditions during three months (Arshad and
Mujahid, 2014). Wool keratin is an ideal substrate for
proteases, esterases, lipases enzymes and those that
act specifically on disulfide bonds. Microbes and insects
can digest wool by secreting extracellular keratinolytic
enzymes that catalyze the hydrolysis of peptide linkages
leading to release of polypeptides and soluble
sulfhydryl-containing amino acids (Cardamone, 2001).
Microbial growth depends upon moisture, ambient
temperature and assimilable sources of nutrients for the
specific organism. Under favourable temperature and
humidity conditions, more than 10 viable bacteria and
4
10 fun g i p e r g o f w ool develo p a n d c a u se
3
biodegradation (Gochel et al.,1992).
In waste wool, mostly fibres are broken which
allow the microbe to attack on the inner cuticle layers
and the lipid-rich complex of membrane cells, thereby
the innermost structural elements, the cortical cells,
become exposed to enzymatic digestion. This
enzy m a t i c d i gest i o n i s f u r ther i n c r e a s ed if
carbohydrates, fats and nitrogen are present in the
Inida
2.5
UK
3.9
Iran
4.5
Turkey
5.9
Argentina
7.0
21.4 New Zealand
U.S.A.
11.9
China
18.6
37.7
Australia
Fig. 1. Relative contribution (%) of countries in total wool
waste production
culture media. Although, environment-friendly and
economical methods of microbial degradation are not
universally used wool waste, it seems to be an attractive
approach to manage these wastes without energy
wastage and amino acids loss (Gupta et al., 2012).
C. Possible application of waste wool in agriculture
(Table 3)
i. Moisture conservation: Wool fibres absorb and
retain moisture very effectively and this property is
beneficial when applied to soils where it can reduce
runoff of contaminants such as pesticides and improve
water conservation. Wool fibres are lighter and can
absorb higher amount of moisture without adding the
weight (Nustorova et al., 2006). Karim et al (2009).
reported that wool retained higher amount of moisture
due to hygroscopic nature. Wool can absorb up to 30%
moisture of its own weight because of polarity of
peptide group, salt linkage and its amorphous nature.
The peptide group and salt linkages attract water
molecule, which readily enter into the amorphous
region of the fibre. Coarse wool can act as water
conservation medium since wool can r et ai n a
substantial amount of moisture (Kadam et al., 2013).
On comparing various forms of wool, Kadam et al.
(2014) reported higher moisture retention of wool felt
due to its consolidated form and uniform density (1000
g/m ) as compared to other form of wool. The
2
consolidated form of wool restricts movement of
moisture due to barrier created between soil layers.
The moisture retention in soil was increased by
23.33% over the control (Kadam et al., 2014). Brian
Gold from Pineae Green houses in Ogden reported
that after seven days, the plant with the wool pellets
had retained about 40% more water than those
without wool pellets (Hargreaves, 2017). He opined
that wool naturally absorbs water about 20 times its
weight, so farmers can conserve more water by
applying waste wool as mulching material in the soil or
bunds.
ii. Organic mulch: Mulch is placed on top of soil
around trees and crop plants. The mulch acts as an
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The wool absorbs water, herbicides, pesticides and
fertilisers, releasing them slowly into the soil. Wool
mats are commercially available in dev el op ed
countries, or one can weave their own mats from
unprocessed wool. Wool carpet waste contains
nutrient elements that can provide fertilising benefit
over and above that of non-biodegradable mulch or
simple organic mulch.
4
insulator and keeps the soil cooler in the summer and
warmer in the winter. It also helps the soil to retain
moisture, limits evaporation and prevents weeds from
germination and g ro wt h in the mulched areas
(Bhardwaj, 2013). Like other mulch materials, wool
suppresses weed growth and acts as a source of N,
and more resistant to breakdown (lasting longer) than
other mulch materials. Wool mulch lasts for two years.
Table 3. Use of wool-waste in agriculture and other sectors
Sector References
Agriculture
Mulching material for improving soil moisture retention, Bhardwaj (2013); Cincinnati et al (2012); Garton et al..
oration and preventing weeds germination (2013)reducing evap
Soil amendments for improving soil condition and nutrient (2003); PughGovi et al (1998); Johnson et al..
content (2007); Zheljazkov et al (2008).
Soil reinforcement amendment Wang et al. (1994); Wang (1997, 2006)
Compost and organic nutrient source Plat et al (1984); Tiwari et al. (1989); Waliczek et.
al. (2013); Hustvedt et al. (2016); Kadam et al. (2014)
Slow release fertiliser Mazur and Malicki (1993); Nustorova et al. (2006);
Michel et al. (2008); Waliczek et al. (2013)
As substrate amendment in pot cultivation of tomato, Gorecki and Gorecki (2010)
sweet pepper and eggplant
Others
Conversion of waste wool to protein for the production of Shavandi et al. (2016)
fibre, film and injectable gel for biomedical applications
Use of waste wool in nitrogen fertilisers Bhavsar et al. (2016); Bhavsar (2018)
Extraction of keratin from waste wool for cosmetic industries Brown et al. (2016)
Cincinnati et al (2012) reported that the eggplants.
( ) that received the wool mulchSolanum melongena
were more resilient to temperature than those that
received hay mulch. These eggplants in wool mulch
also had darker leaves, greater vitality and higher
yield. The soil under the wool mulch is cooler than that
under hay mulch. Sweet potato ( )Ipomoea batatas
mulched with wool produced 536 pounds compared to
just 145 pounds in the row mulched with hay. Wool
mulch had less temperature fluctuation than in hay
mulch or no-mulch. Nitrogen levels in the tissue
samples were highest in the wool mulch and the
lowest or deficient in the hay mulch. At West Virginia
University, Morgantown, Garton et al. (2013) reported
that in organic tomato production, wool applied as
mulch at a depth of 5 cm, yielded significantly higher
than other treatments or control. As wool is able to
absorb water and biodegrades slowly it makes good
mulch, particularly for young trees and shrubs
(Pollard-Jones, 2016).
iii. Soil amendment and organic nutrient source:
Anecdotal records of gardeners from 1940s had
suggested beneficial effects of wool on growth of
plants (Waliczek et al., 2013). Earlier, it was believed
that wool would not break down in soil. Researchers
tried experiments by adding some wool in hanging
baskets around plants and compared it with other
plants (Hargreaves, 2017). They found beneficial
effect on plant growth, further used pellet of wool for
making best use of wool in soil amendment. Limited
research on the use of poor grade wool for agricultural
crops has been carried out (Zheljazkov, 2005). It was
reported that amending soil with sheep wool improved
productivity of plant species (Zheljazkov, 2005;
Zheljazkov et al., 2008).
Wool is a rich source of important nutrients which
are necessary for plant growth (McNeil et al., 2007). It
contains high quantities of N, S and C. Sheep wool
S.C. Sharma et al.
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hy d r o lysate i m p r oves gr o w i ng condi t i o ns by
increasing contents of total N, C, and P in the soil (Govi
et al , 1998). In an experiment on the use of waste.
wool carpet to improve the pasture land, Johnson et al.
(2003) found increased levels of sulphur by 25%,
magnesium by 17%, potassium by 15%, nitrogen by
10% and phosphorous by 7% in grass after 10 weeks
of seeding on soil with ground-up wool carpet
compared with grass grown on soil with no wool. The
dry weight of grass after 15 weeks was 24% more from
the carpet-fertilised area. The wool in carpet contains
significant amounts of N and S. Major elements
reported for carpet wool waste are 5.5 to17.0% N, 1.2
to 3.5% S and 10.8% Ca (McNeil et al., 2007; Mesman
et al., 2007). Out of which N and S contents are
comparable to farmyard manure, but it has low
contents of phosphate, potash and magnesium (Pugh,
2007). Further, McNeil et al. (2007) found suitability of
wool wastes as fertiliser with elevated levels of
essential elements such as N (19%), S (19%) and Mg
(7%) in the grass grown on wool fertilised plots as
compared to the control. The addition of wool-waste to
the growth medium increased Swiss chard (Beta
vulgaris Ocimum basilicum) and basil ( ) tissue N, and
NO -N and NH -N relative to the un-amended control
3 4
(Zheljazkov et al., 2009a).
There is significant evidence that incorporation of
car p e t w a s te ma y i m p r o ve so m e s t r u ctu r a l
characteristics of soil a s well as water-holding
capacity. In a series of research papers, Wang et al.
(1994) and Wang (1997, 2006) investigated the use of
fibres in soil and recorded an increase in tri-axial
compressive strength that have relevance in unstable
and sandy soils.
In an exper iment with the hydrolysed wool,
Nustorova et al (2006) found that the C:N ratio in.
treated soil increased with increasing doses of wool.
This was also reflected by an increased mineralization
of hydrol ysa te by m icroorga nis ms in t he soil.
Zheljazkov (2005) and Zheljazkov et al (2008).
reported that addition of wool waste to soil increased
NH -N and NO -N in soil and stimulated soil microbial
4 3
biomass. They further observed that high rates of wool
addi tio n to soil resu lte d in shif ts of m icrobial
composition, while a low rate of wool-waste addition
did not affect the microbial composition relative to the
un-amended. Amendment-fertilisation of grassland
contributes to the reduction of soil degradation,
including erosion. Pot experiment involving waste wool
have proved it as a good source of N (Hodnik et al.,
2008).Coarse wool provided significantly higher
quantity of available nitrogen, phosphorus and potash
for plants. However, micronutrient availability and
other soil properties like soil organic C and pH were
unaffected by wool application in any form (Kadam et
al 2014). Another advantage, wool soaks up in the.,
soil, it fluffs up and expands, increasing soil porosity
and improving the soil's ability to retain oxygen (Kadam
et al., 2014; Hargreaves, 2017).
iv. Composting of waste wool: It is one of the best
options for soil amendments and provides farmers with
additional income, and provides communities that
depend on sheep for best use of waste wool. Wool-
waste requires composting prior to use as soil
amendments, largely to provide appropriate substrate
qualities for plant growth, including lowering of C: N
ratios and the provision of available plant nutrients
(BSI, 2005). Tiwari et al. (1989) used wool-waste
compost at 10 t/ha in a growth study involving chickpea
and wheat crops and found a trend in response with the
reduction in C: N ratios. Waliczek et al. (2013)
constructed compost piles incorporating wool-waste
with proportions of various other feedstock ingredients
including animal manures, food waste, invasive river
plants and horticultural plant green waste, as well as
tree-pruning waste and livestock bedding and straw.
Plat et al (1984) suggested the utilization of wool-.
waste in compost form, as N source for plants and
Tiwari et al (1989) reported a marked response in.
chickp ea and whea t growt h using woo l-waste
composts and they further noted maximum responses
in nodulation and pod formation in chickpea and also
in yield of wheat crop by the application of 10% dung
and 2% rock phosphate treated wool-waste compost.
The composting in this way results in an immediate
immobilization of nutrients, especially N. Further,
Use of waste wool in agriculture
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Zheljazkov et al. (2009b) used un-composted wool-
waste as a nutrient source for both container grown
crops and field crops and concluded that wool-waste
as an excellent soil amendment that increased plant
yields and essential nutrient contents. Mubarak et al.
(2009) found that decrease in water movement in
sandy soils amended with organic residues including
carpet wool wastes, offered better chance for crops to
absorb water and nutrients. They found an increase in
plant yields up to 28% dry matter (DM). It is also
interesting to note that wool has greater imbibition for
water since soil moisture content at harvest was
greater t han w ith out w ool a mendment , whi ch
emphasizes wool ability to stabilise soil. Recent
research has established that wool or hair
incorporated into the pot plant environment can
improve the water-holding capacity of the soil as well
as act as a slow-release fertiliser (Waliczek et al.,
2013). Hustvedt et al. (2016) determined that a 25%
waste wool, 50% grass clipping, and 25% horse stall
waste mixture provided the optimal results for
composting. Compacted wool, if transported in
wrapped bundles, proved better decomposition of the
waste wool. The authors recommended a ratio of
sheep wool-waste, fallen tree leaves/weeds and
grasses (agricultural farm waste/crop residues) and
sheep faecal pellets at 30:20:50 for its efficient
composting and quality manure production.
ICAR- CSWRI, Avikanagar has conceptualized the
idea of utilization of waste wool in agriculture for its
safe disposal by composting with sheep manure and
other agricultural by-products (S.C. Sharma, L.R.
Meena and R.C. Balai, 2012; S.C. Sharma, R.C. Balai
and A. Sahoo, 2017, Personal communications). A
series of experiments were carried out and obtained
encouraging results in terms of moisture retention and
higher biomass yield. In an incubation study in 2012,
sheep manure: wool dust (1.00:1.00 part) when
incubated for 45 days resulted in improvement in pH, N
(1.31 to 3.03%), P (0.42 to 1.47%), K (0.93 to 1.43%),
Fe (33.45 to 95.2 ppm) and Cu (21.03 to 48 ppm) of
sheep manure. In subsequent years, waste- wool-
based manure has been developed by composting
50% sheep manure, 30% waste wool, 20% crop
residues/dry tree leaves with compost inoculants and
named as 'Avikhad'. The Institute has also got
'copyright' for 'Avikhad and 'Organic Certification' from
Rajasthan Organic Certification Agency (ROCA),
Jaipur in 2016. It has multiple benefits: a) use as
fertiliser, b) improves retention of water to facilitate its
slow release of nutrients to the crop, c) minimises
frequent watering due to longer duration of moisture
retention, d) for organic produce and finally, e)
reducing environmental pollution (Fig. 2). This has
opened up wide use of wool waste application in urban
horticulture/ floriculture, pot-culture (indoor and
outdoor ornamental plants in pots) and making of
green environments in multi-storey buildings/malls,
corporate offices, airports and other establishments in
metro-cities. Further, in 2016 and 2017, comparative
scientific evaluation on the use of Avikhad, sheep
manure and waste wool was made on plant growth
performance involving oats and barley crops in Rabi
season (S.C. Sharma, A. Sahoo and L.R. Meena,
2018, Personal communications). Two types of wool-
waste i.e. shearing waste and wool processing
machine waste at 40 and 60% soil moisture saturation
level were studied. It was observed that height of crops
and dry matter accumulation increased considerably
Improves
N and S
contents
Checks
pollution
Slow
release
manure
Source of
organic
manure
Improves
water
retention
Wool
waste
Fig. 2. Multiple benefit of wool-waste in agriculture
S.C. Sharma et al.
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with Avikhad in comparison to sheep manure under
both type of waste-wool application in low-carbon
sandy soil of Rajasthan.
v. Slow release fertiliser: Most of the inorganic
fertilisers are nowadays costly and subjected to many
types of losses resulting in poor use efficiency.
Further, these fertilisers are hazardous when used in
excess causing soil pollution. However, as organic
fertiliser from wool-waste is a rich source of important
nutrients (N, S and C) for plant growth, it is imperative
to explore its environmental-friendly usage. The wool
and its by-products are richer in organic N (over 5%)
and C (30 to 50%) than manure and compost (Baker,
1991). Sweat wool before processing contains fats,
dirt, and other compounds like weeds, faeces, etc. As
th e pres enc e of fat s dela yed m i cro biol ogic al
decomposition, raw wool is less suitable for amending
growing substrates in short-term vegetable cultivation
under glass. Also, sweat wool is hydrophobic, so the
amount of water and nutrient solution, it absorbs is
smaller (Mazur and Malicki, 1993;, Michel et al., 2008).
As mentioned, one of the main qualities of wool is
biodegradability, when buried in soil, the keratin
biopolymer is degraded by microorganisms and
releases nutrients essential to the crops. Because
wool slowly decomposes in soil it can be used as a
slow-release fertiliser, and act as a source of N-based
nutrients and S over a longer period than conventional
fertilisers. Low grade raw wool or wool waste can be
used as agricultural amendments, laid directly in the
bottom of the plant pits, or added to the compost
mixture, to improve the N content and water retention.
Green hydrolysis using super-heated water is an
emerging techno log y to tu rn wa ste w ool i nto
am end men t-f ert ili ser s for t he ma nag ement of
grasslands and other cultivation purposes (Zoccola et
al., 2015). In this way wool keratin is degraded into
simpler compou nds, increasing the r el ease of
nutrients to plants.
Scanning electron microscopy (SEM) and energy
dispersive X-ray (EDX) analysis demonstrated that
wool wastes decompose slowly under field or
greenhouse conditions, and act as a slow release S,
N, P, and K fertiliser. These results, along with the
measured concentrations of NO -N in soil at harvest,
3
suggested that addition of wool or hair waste @ 3.3
g/kg of soil supports two to five harvests of crops
under greenhouse conditions and two to four seasons
in the field, and improved soil biological and chemical
characteristics (Zheljazkov, 2005). Hargreaves (2017)
reported 9%N, 1%P, and 2% K in wool pellets, which
takes months to break down, and act as a natural,
slow-release fertiliser.
D. Effects on plant chemical composition, growth
and yield
The use wool or its hydrolysate on chemical
composition and performance of plants has been
presented in Table 4. Zheljazkov (2005) reported that
addition of wool-waste to soil increased total N (and
protein) content in plant tissue. Wool-waste additions to
soil altered slightly the content and composition of plant
secondary metabolites (essential oils or alkaloids);
however the overall constituents remained within the
normal range for the respective crops. McNeil et al.
(2007) found that content of Ca did not change in
ryegrass plants due to fertilising with post-consumer
wool carpet, content of Mg did not change or increased
7% (depending on the number of days after planting),
whereas content of P (35 and 10%) and K (8 and 8%)
decreased. On the other hand, Nustorova et al. (2006)
reported that due to the amendment of wool
hydrolysate, content of K, Mg, and Ca increased in the
biomass of ryegrass collected during the first mowing,
whereas content of these elements in the biomass of
ryegrass from the second mowing decreased. Gorecki
and Gor ecki (2010) reporte d that due to wool
amendment to the substrate, content of N-NO and K
3
decreased by 49 and 42%, respectively in tomato
leaves, whereas content of P, Mg, and Ca increased by
19, 15, and 25%, respectively. It may be concluded that
waste wool is a valuable fertiliser in production of many
species of plants. Applied hydrolysed wool also
improved emergence and plant growth (Nustorova et
al., 2006). The addition of unwashed and cut wool
Use of waste wool in agriculture
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showed similar positive results on marigold and basil
plants(Zheljazkovet al., 2009b).
Wool, when added to the soil, greatly increases the
yield (wet and DM) of grass. The known disadvantages
of wool-wastes in grassland are inherent handling
problems, lack of ready availability nutrients, weed
problems and low bulk density (Das et al., 1997).
Zheljazkov (2005) reported that addition of wool waste
to soil increased yields of basil ( L.Ocimum basilicum
'Trakia'), thorn apple ( Mill. 'Inka'),Datura innoxia
peppermint ( x L. 'Black Mitchum') andMentha piperita
garden sage ( L. 'Desislava'). PlantsSalvia officinalis
cultivated in wool-amended soil yielded 40-142% more
yields. Literature shows that wool, when used as a
fertiliser, increased the DM yield of grass between 24 to
82%. The grass grown on plots fertilised with wool
appeared a dark shade of green than the grass grown on
the control plots (suggesting a healthier state), with
elevated levels of essential elements such as N (19%),
S (19%) and Mg (7%). The increase in N in the fertilised
grass showed that the N in the decomposing wool,
which is an essential element for grass growth. The
increased S in the fertilised grass is valuable for wool
growth in sheep, as S is a major component of wool,
representingabout 3% by weight(McNeil et al , 2007)..
McNeil et al. (2007) found the suitability of ground-
up wool carpet as fertiliser in cultivation of Italian
ryegrass ( ). Fertilised grass yieldedLolium multiflorum
33 to 95% higher (depending on the number of days
after planting). Bohme et al (2008) successfully used.
wool - coconut fibre slabs for cucumber cultivation. In
general, cucumbers grown in wool yielded 19-42%
more than plants cultivated in coconut fibre slabs. In
cucumber plants in wool-containing slabs, additionally
treated with bio-stimulators, yield increased by 130%.
Also, alkaline hydrolysate of waste wool used as soil
fertiliser increased biomass of ryegrass and seed
germination, as well as improved microbial life of soil
(Gousterova et al , 2003; Nustorova et al., 2006)..
Zheljazkov et al. (2008) conducted pot and field
experiments to assess un-composted wool-wastes as
a nutri e n t s o u r c e f o r n o n - e d i b l e h i g h -value
crops / p l a n t s . They in f e r r e d t h at in the p o t
experiments, addition of un-composted wool to soil
increased yields from marigold (Calendula officinalis
L ) and valerian ( L ). In the field. Valeriana officinalis .
exp eriment, wool-waste when added to purple
foxglove ( L ) at rates of 0, 15.8 andDigitalis purpurea .
31.7 t/ha increased yields in two seasons by 1.7 to 3.5
times compared to the control. The addition of un-
composted wool-waste at 0.33% by weight to soil
meet the requirements of nutrients for at least 2 to 3
harvests of crops, without the addition of other
fertilisers. Thus, un-composted wool can be used as a
nutrient source for high-value crops. Zheljazkov et al.
(2009a) reported that un-composted wool-wastes
could be used as nutrient source and growth medium
constituent for container-grown plants. Total basil
yield from the five harvests was 1.6-5 times greater
than un-amended control, while total Swiss chard yield
from the four harvests w as 2 -5 times greater
compared to un-amended control.
In a study of tomato, eggplant and pepper in an
unheated greenhouse, Gorecki and Gorecki (2010)
obs erved that substrate amendment with wool
contributed to a significant increase in tomato fruit
yield. The effects were taller plants, higher fresh
weights of plants and more green appearance of
leaves. Also, prolonged the vegetation period and
delayed ageing. They further reported that addition of
clay soil to the basic peat substrate decreased tomato
plants fruiting, but enrichment of this substrate with
sheep wool increased the yield by 29% as compared
to the control substrate. In the case of eggplant, the
addition of wool to culture substrate did not increase
the yield, but insignificantly increased the number of
fruit s ( b y 1 4 % ) . P e p p e r r e s p o n d e d t o w ool
amendment into substrate and yielded 30% more and
fruit number by 16%. Voncina and Mihelic (2013)
observed highest soil N and asparagus (Asparagus
officinalis L.) yield in th e fir st ye ar fo llo win g
incorporation of wool. Further, NO -N content in the
3
asparagus crop was low reflecting the good synchrony
of N mineralization and consumption of N in wool
incorporation.
S.C. Sharma et al.
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Table 4. Effects of adding waste-wool to soil on crop performance at various locations
Crop Effect on crop performance Reference
Swiss chard ( ), basil The addition of wool-waste to the growth Zheljazkov et al. (2009a)Beta vulgaris
( ) medium increased tissue NOcimum basilicum
Ryegrass ( ) Amendment of wool hydrolysate increased Nustorova et al. (2006)Lolium multiflorum
K, Mg and Ca content in the biomass of ryegrass
Wool fertilised grass yielded 24 to 82% Gousterova et al (2003);.
more DM with elevated level of N (19%), McNeil et al (2007).
S (19%) and Mg (7%)
Tomato ( ) Wool amended plot resulted in 19, 15 and Gorecki and Gorecki (2010)Solanum lycopersicum
25% higher content of P, Mg, and Ca,
respectively in tomato leaves
Basil ( ), thorn apple Wool-amended soil yielded 40-142% more Zheljazkov (2005)Ocimum basilicum
( ), peppermint ( yieldsDatura innoxia Mentha
piperita Salvia officinalis .), garden sage ( ) Cucumbers grown in wool containing slabs Bohme et al (2008)
cucumbers ( ) yielded 19-42% more yieldsCucumis sativus
Foxglove ( ) Wool additions to soil increased foxglove Zheljazkov et al. (2008)Digitalis purpurea
yields over the next two seasons by 1.7 to
3.5 times
Basil ( ), Swiss chard Wool amended plots gave basil and Swiss Zheljazkov et al. (2009a)Ocimum basilicum
( ) chard yield 1.6-5 times greater than theBeta vulgaris
unamended control
Eggplant ( ), tomato Wool amended substrate increased Gorecki and Gorecki (2010)Solanum melongena
( ), pepper ( number of eggplant fruits by 14%, tomatoSolanum lycopersicum Piper
nigrum) yield by 29% and pepper yield by 30% and
fruit number by 16%
Barley ( ) Growth, green fodder and grain yield Kadam et al. (2014)Hordeum vulgare
markedly increased using coarse wool at
different depth under soil
In a study of tomato, eggplant and pepper in an
unheated greenhouse, Gorecki and Gorecki (2010)
obs erved that substrate amendment with wool
contributed to a significant increase in tomato fruit
yield. The effects were taller plants, higher fresh
weights of plants and more green appearance of
leaves. Also, prolonged the vegetation period and
delayed ageing. They further reported that addition of
clay soil to the basic peat substrate decreased tomato
plants fruiting, but enrichment of this substrate with
sheep wool increased the yield by 29% as compared
to the control substrate. In the case of eggplant, the
addition of wool to culture substrate did not increase
the yield, but insignificantly increased the number of
fruit s ( b y 1 4 % ) . P e p p e r r e s p o n d e d t o w ool
amendment into substrate and yielded 30% more and
fruit number by 16%. Voncina and Mihelic (2013)
observed highest soil N and asparagus (Asparagus
officinalis L.) yield in th e fir st ye ar fo llo win g
incorporation of wool. Further, NO -N content in the
3
asparagus crop was low reflecting the good synchrony
of N mineralization and consumption of N in wool
incorporation.
Kadam et al. (2014) reported that the plant growth
of barley crop in terms of plant height, tillers/plant, leaf
area and number of leaves/plant was better for the felt
wool at soil depth of 30 cm than 15 cm. It might be due
to the higher moisture retention by the application of
wool. The wool felt had more pronounced effects
upon plant growth as compared to other forms of
wool. The leaf area of wool felt plot and control plot
differed significantly, while plant height and number
of leaves/plant were significantly in felt plot over mat
plot. This increase might be due to better root growth
and higher moisture availability. It was reported that
higher root growth, distribution in mid and deep soil
improved t he uptake of wa ter from deep s oil
(Kwabiah, 2004; Lalitha et al , 2010). Addition of.
coarse wool in different forms and at depth in soil
Use of waste wool in agriculture
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resulted in significant (P<0.05) improvement of
green fodder and grain yield of barley. It could be
attributed to consolidated and stable form of wool felt
which had provided required moisture for plants
during the growth stage. Delayed degradation of
wool often has advantage in the second cropping
cy c le as th e f ollow - up deg r adat i on prov i des
significantly more N than the same dose of N from
farm yard manure.
E. Other agricultural benefits
No n-wo ven wo o l mat s a re pla ced ar ound
seedlings to inhibit weed growth when the plants are
young and then it breakdown and fertilise the soil as
the trees grow (Johnson et al., 2003). Wool in non-
woven form can be also used as weed-mats (Hempe,
2014). Pollard-Jones (2016) also mentioned that wool
mulching helped in keeping the weed competition low
for water and nutrients as it acts as barrier for weeds. It
serves as a natural repellent (Cincinnati et al , 2012)..
Hargreaves (2017) reported that wool can be used to
repel snails. Composting also removes parasites and
pathogens and to some extent degrades potential
contaminants (Cogger, 2005).
F. Conclusion
Waste sheep wool is a valuable fertiliser for the plants
and has got enormous possibility of organic manure
production that ultimately helps in organic animal
produce. Both sweat and washed wool (also wool
carpets) and its hydrolysates appeared to be valuable
and environmental friendly fertilisers. The feasibility of
recycling of used carpet / waste wool to the soil as a
fertiliser, help to grass growth and thereby help to grow
more wool in a closed-loop system, i.e. Grass Wool
Carpet Grass. Composting is generally used both as a
waste management alternative and a horticultural and
agricultural resource. It is a low-energy-input system
and the biodegradability properties have potential
applications in geo-textile products. To increase the
economic, environmental and social sustainability of
wool production, composting the waste wool into soil
amendments and landscaping can provide producers
additional income, an d pride to sheep farming
communities inthe value of all parts of thelife cycle.
This literature review has shown that there is limited but
significant evidence to show wool-waste, a likely and
promising source to provide b enefits as a so il
amendment, in terms o f i m p r o v i n g p h y s i c a l
characteristics and soil fertility. Nitrogen contents are
relatively high and S could be added to soil without
lowering pH. Clearly the use of waste wool as a fertiliser is
a new concept. Further studies are required to establish
the most effective application rates and the dynamics of N
release in order to synchronise the complex interaction of
itsavailabilityanddemandby theplants.
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