|
4 Pesticides
Pesticides are chemical substances that aim at fighting off the
enemies and the diseases afflicting cultivated plants. They are
toxic substances that lead the aforementioned species to death.
The
objective of the use of pesticides was the protection of production.
They were very important in protecting human lives as well. Dajoz
mentions that in the winter of
1944 the use of pesticides (and specifically, that of the strong
substance of DDT) allowed the restrain of the typhus epidemic that
led to the death of 1.400 people, and threatened 2.500.000 others in
the Naples area. The control of malaria is also the result of
pesticides.
The field of plant protection products is ruled by a small number of
large multinational chemicals companies, since from
1987 ten (10)
companies achieved 70% of the world production in products for plant
protection (Loumou, 1998). Today in developed countries plant
protecting products with high toxicity and high concentration of
remainders are regarded especially dangerous in the frame of the
policy for consumer and environmental protection, and measures are
taken for the prohibition of their use and production.
Pesticides can be divided into
5
basic categories according to the biological “enemy” of plants that
is fought. These categories are the followingι:
insecticides, fungiscides, pesticides, rodentcides and nematocides.
As far as their usage is concerned we focus on the following:
·
They have a broad toxicity
spectrum for animal and plant species.
·
They are applied against
certain organisms (0,5 of the total species of a system) but have a
different degree of effect on the various living organisms.
·
Their results are
independent of the density of the fought population, but are used
only when the level of population that has the adverse effects has
reached a high point. Therefore, the period of application depends
on the population density.
·
The quantities used are
usually higher than the ones necessary.
·
The surface on which they
are usually used take up large areas.
·
A large number of pesticides
remains in the ground for months, or even years.
·
Even the milder pesticides
are carried through their emission by the wind to other cultivations
even until the sea, and appear in areas where they have never been
used. This phenomenon is observed during water pollution too.
Pesticides are carried through the water in areas that have not
immediately treated.
Pesticides, after they have been used in plants or in the soil,
undergo a series of procedures, physical, chemical and biological
(hydrolysis, oxidization, fission, transfer, evaporation, root
admission by the plants etc.) and pollute the soil, the waters and
through those, are being transferred to plant and animal tissues
even in humans (McMinn
et al.,
1983; Erehse, 1974). Today there’s enough proof that the molecules
of many pesticides and especially chlorine-pesticides, are being
sustained in the ground and water for years or even decades and
their concentration from very small particles in the water (a third
millionth), can be bio-magnified 105-107 times in the tissues of
invertebrates, fish, birds, and mammals and the final concentration
will reach millionths (ppm) in animals (Angelides, 1982).
Another problem arises due to pesticide residues in the soil, a fact
that very often obstructs the change of cultivations for years and
causes problems due to toxic remains in agricultural products. The
soil poisoning from pesticides has gone so far that, even if their
use is abandoned today, the restoration of soil is costly and
requires intensive projects. Soils have been found that contain up
to 2 kilos DDT per quarter of an acre, many years after its last use
(Carson, 1962). That’s why it is estimated that as long as there is
such uncontrolled use of pesticides, the risk of soil contamination
will continue.
Special
reference is made to “poisoning” from accidents and in production
areas or through use and application of pesticides. As far as human
poisoning is concerned, according to the W.H.O. research, it is
estimated that every year approximately
1-1,5 million people are poisoned, and among those around
5.000-40.000 people die (Politis, 1992).
As far as
environmental pollution is concerned, the case of Sobezo in Italy is
mentioned, where in
1976, due to dioxine leakage
the area was evacuated the new class of «environmental refugees»,
while a large number of the citizens of the area died; additionally
cancer incidents and monstrous deformations were observed.
Furthermore, during 1987 in Switzerland there was an “accidental”
discarding of pesticides in the Rhine, where not only a large number
of creatures of the river were destroyed but also irrigation and
water supply problems were caused (Albadis, 1988).
4.2
Effects from the Use of Pesticides
The
adverse effects of pesticides in agriculture are important for the
broader ecological spectrum and more often broader than initially
estimated.
4.2.1
Results from the Use of Pesticides into the Biological Community
Pesticides, even when used for fighting off a specific plant enemy,
can bring about substantial changes to the whole ecosystem. The
disappearance of even one organism from the ecosystem leads to the
alteration of its character and the destabilization of balances
based on a series of biological controls developed through time.
4.2.2
Decrease of Available Foodstuffs
The fight
against a biological enemy in cultivations reduces the food for
other organisms that are reduced as well, and so on. The reduction
of flora in the cultivated area also reduces fauna, due to the lack
of food and the difficulty in creating nests. Similar phenomena
appear in water pollution. The disappearance of zooplakton and
insect nymphs leads to the starvation of water fauna.
4.2.3
Decrease of Competitors
The
obstruction of species development, that under normal circumstances
compete in the development of others, allows the multiplication of
the last. Therefore, species that are already found in small
populations before the use of pesticides, due to the disappearance
of their competitors show enormous population increase. For example,
the fight against dicotyledon
weeds in cereal cultivations gave monocotyledons the
opportunity to develop; these in order to be extinguished, need more
specialized chemical substances, and are generally hard to
exterminate due to their affinity with the cultivated plants.
4.2.4
Decrease of Biological Invaders
Toxicity
resulting from pesticide application appears not only on the direct
target but on many useful organisms that will contribute to the
sustainability of the ecosystem (biological enemies and pollination
agents). Therefore, the destruction of bio-communities due to the
use of pesticides, often leads to the increase of population and its
intensification. An example of those disturbances is the application
of pyrethrinoides in cotton cultivations for the fight against
lepidoptera insects, when at the same time the biological enemies of
spider mite disappear, resulting in an increase of spider mites in
cotton cultivation.
The
disturbances caused in the bio-community, constantly increase the
dependence of cultivations on pesticides and lead to the continuous
increase of the quantities used.
4.2.5
Decrease of the Biodiversity in the Biological Community
The
decrease in the bio-diversity of the bio-community is obvious during
the use of pesticides and leads to the extinction of species in the
cultivated areas as well as in those areas that are on the
periphery, a phenomenon that is intensified with the application of
monocultivations. A typical example is that of the change in the
appearance of the forests of Vietnam after the use of big quantities
of pesticides from the American army.
4.2.6
Effects on Species Succession
Usually
the succession of animals species depends on that of plants,
therefore pesticides have again an important role to play in the
succession of animal species. Non-selectives act like fire, more or
less, bringing the ecosystem to a stage of primordial colonization!
Pesticides do not only destroy biological enemies of cultivations
but also destroy pollination agents. This destruction (bees etc)
leads to the reduction of yields in insect pollinated cultivations.
Finally, it should be underlined that the use of pesticides brings
about an addiction to the species being treated, resulting in the
appearance of resistant clones. It is a fact that insects, due to
their fast reproduction, short life-cycles, and genetic diversity
develop an ability to overcome the efforts of being controlled
chemically. Today, there are over
450 insect species that are resistant to many pesticides.
The usual
measure taken by farmers for dealing with this situation is an
increase in the quantities used, or that of intervention usually
with more toxic pesticides, resulting in the intensification of the
phenomenon. A typical example is the case of cotton cultivators in
Thessaly and Macedonia, (Greece) (1999),
where the green caterpillar’s resistance to the usual pesticides got
stronger. Farmers, faced with the danger of destruction of their
production used large quantities of various pesticides, which
resulted in serious pollution to the soil and surface waters.
4.3
Effects of Pesticides on Health
Pesticides, partly considered responsible for the increase in global
agricultural production, are threatening the health of farmers as
direct users, and of the consumers, through the use of these
products and the pesticide residues still remaining in them, as well
as for the natural balances of this planet. There is a huge list of
cases where pesticides have been found in foodstuffs: fruits,
vegetables, milk and milk products, eggs, livestock products,
cereals and fish, items included in daily diet. In some foodstuffs,
residues of lot of different pesticides were found, some of which
they have a long-term residual action (Nriagu and Simons,
1990).
Pesticides, according to researches conducted by the World Health
Organization (WHO), are causing poisoning in
1-1,5 million people globally every year; these people may be the
farmers using them, workers producing them, or consumers of
agricultural products, recently sprayed with pesticides. From these
cases 20.000 every year result in death.
The major
effects of pesticides in health are (Almpanis,
1988):
-
Central
neural system impairment
-
Dermatitis, burn and other skin diseases
-
Stomach
disorders and poisonings
-
Weakness, dizziness, foot paralysis
-
Respiratory system impairment
-
Alterations in liver and kidney operation
-
Accumulation of toxic metabolites
-
Accumulation in mutagenic
and cancerous action
-
Cancer
(prostate, stomach, esophagus, lungs, mouth, skin, respiratory
system and lymph)
-
Inhibition of many biological operations of the human body
-
Synergistic action
with smoking and alcoholic
drinks
It must
be underlined that pesticides can be spread very easily and can be
transferred to the rivers and seas. They are characterized as hardly
biodegradable, thus securing their long-term existence in natural
ecosystems. Furthermore, they have the quality of biological
magnification, thanks to which, climb up the food chain the final
concentrations of pesticides in the body of birds and mammals can be
few million times higher from the initial concentration in its base
(water, phytoplankton, plants). The most tragic evidence of this
evolutionary process is the fact that these substances end up in the
human body, through natural forage and fat from fish, poultry and
beef.
5
Agricultural Waste Management
5.1
General
In many
European countries agricultural by-products and wastes of
agricultural industry activities are dumped as useless, and are
usually a source of environmental pollution. Of particular
significance is groundwater pollution
from agricultural waste, and furthermore, to drills used for
irrigation or water supply,
The most
important elements to be considered and evaluated regarding
agricultural pollution are: the design and planning of agricultural
and livestock activities, the distance from water sources, the
overall condition of drills, storage conditions, and the management
and disposal of possible pollutants and toxic substances in a farm.
By
defining and assessing the pollution risks on farms and the
improvement of management practices, the animal, plants and human
health are protected and possible pollution of the water table is
averted. A possible
abandonment of the property
is at the same time discouraged, while the production of safe and
quality agricultural products is guaranteed.
Surface
water pollution has multiple effects at all levels of an ecosystem.
It can cause health problems in organism’s lying at the lower levels
of the food chain, and consequently, in food availability in the
middle and upper levels of the food chain. It can also cause the
degradation of wetlands and limit their ability in supporting the
local ecosystems and control of the quality of drainage water. The
contaminated surface water can have negative effects on animal and
human health.
Agricultural wastes include both organic (natural) and non-organic
(not natural) by-products of agricultural activities.
The
organic agricultural wastes (solid, liquid or semi solid) include:
natural residues (cereal straws, corn and cotton stocks, grapevine
stem etc), animal residues (manure and uric residues of the animal
and poultry capital, bedding
etc), as well as, agro-industrial wastes, such as
residues of oil olive production and citrus fruits industries.
Main
non-natural agricultural wastes include: plastic bags of
fertilizers, seeds, pesticides and other agrochemicals, veterinary
products and materials (e.g. used syringes), mechanical residues
(e.g. oil, car tires and batteries), old machines, fencings etc.
Even
though the quantity of agricultural wastes is significantly smaller
compared to urban or industrial wastes, the pollution risk by
agricultural wastes is high in the long term. For example,
fertilizers can cause water and soil contamination, while animal
manure constitutes a possible source of dangerous pathogens.
Many farm
by-products can be economically valuable resources if managed
correctly, complying at the same time to environmental guidelines
and regulations. The utilization of these raw materials, residues or
by-products, which are usually of low or negative cost, can reduce
production costs and increasing employment.
There are
different methods used for the process of restoration and disposal
of agricultural wastes, depending on the circumstances. These
include their re-use in the farm, their disposal in the soil (common
burying), their use as fertilizers, their burning, their return to
the suppliers and their anaerobic digestion.
According
to a research conducted by the Environmental Agency, two thirds (2/3)
of wastes are buried or burnt in the farm. However, these practices
are no longer viable or desirable.
The main
goal of the Waste Management policy is the prevention and reduction
of waste production (quantity reduction), as well as the reduction
of dangerous substances in their content (quality improvement). The
policy also aims at the use of waste materials through recycling and
energy retrieval maximization. The wastes that are not utilized and
the wastes resulting from management processes must be provided in
an environmentally acceptable way.
The
principle of vicinity applies during the distribution of wastes.
According to this principle, the wastes must be discarded in one of
the nearest suitable locations. The restoration of dumping areas
that do not fulfill the requirements and are not selected for being
developed in organized places for landfill, must be imposed. In this
case the objectives should be (a) the drastic reduction of
environmental damage in these areas, and (b) the creation of the
right conditions for their re-incorporation in the surrounding
natural environment.
Bearing
in mind the cycle of life of one product from its manufacturing
until use, the producers, the suppliers of the material, the
merchants, the consumers and the public authorities are responsible
for waste management. However, the producer plays the major role. Is
the one deciding about/on issues directly related to the creation
and management of the product, like the design, the use of special
materials, the making and promotion of the product. Therefore, the
producer is in position, urged by expedient incentives and strong
disincentives given by the Public Authorities, to take measures, on
the one hand, for the achievement of prevention, and on the other,
for the production of products provided for reuse and retrieval.
An
agricultural waste management system is a system in which the
installation and management of the elements is done in such a way
that agricultural production by-products are controlled and used in
a way that supports or/and improve the quality of air, water, soil,
settlements and animal resources, consequently, supporting the
management of all wastes, all year round.
The main
goal of agricultural operations is the production of merchantable
worldly goods. To achieve successful production the farmer must
manage limited resources adjusting them to complicated and
interdependent systems like the maintenance of the equipment
systems, irrigation systems, management of animal capital, parasites
control, management of drainage systems, products storage and
economic management. Consequently, a practical waste management
agricultural system must be designed in such a way, that it takes
into consideration all the aforementioned systems, which may cause
environmental degradation.
The
following factors must be considered during the design of a wastes
management system:
(α)
Soil Soil is
the means used more often for the disposal of agricultural waste.
The wastes that can be buried in the soil should not exceed the
soil’s capability for absorption and storage. Furthermore, the
quantity of the wastes applied per year should not exceed the soil
infiltration rate, because it cans possible lead to run-offs that
may cause erosion.
(b)
Water The
potential factors for groundwater pollution and contamination from
agricultural processes includes nutritional substances such as
nitric salts, pesticides and bacteria. The corresponding
factors of surface water from agricultural processes are nutritional
substances, nitric salts, other agricultural chemical substances and
bacteria. The common goal for design of an agricultural waste
management system is to “ capture” the contaminated water for
processing.
(c)
Air Also, the
limitation of the degradation of air quality must be studied.
Therefore, the minimization of ammonia and other gas emissions from
cultivation processes – including natural processes of the animal
capital, odors from the animal capital and waste storage locations
must be considered.
(d)
Agricultural Settlements
The agricultural settlements constitute a significant factor in the
design of an agricultural waste management system.
(e)
Society The
security of people, and its social acceptance must be ensured.
(f)
Economic Effectiveness
Another important factor to be considered is the economic
effectiveness of waste management.
5.4
Agricultural Waste Management Methods
The
remains of plowed crops should not be destroyed or removed from the
field because they can protect the field from erosion, enrich the
soil with organic materials, contribute to the retention of more
rainwater, reduce evaporation and retain moisture.
The waste
products of cultivation, plastic groundsheets, empty fertilizer
packages, pesticides, old and disused materials for irrigation,
fencing or parts of agricultural machinery, should not be left in
the fields or in communal areas but should be collected and
discarded in specially designated areas.
The waste
management of stockbreeding operations are governed by Directive No
91/676, according to which,
waste management depends on the species of the animals breeded,
their number, the way of animal stabling used, the way of collection
and removal of waste from the breeding areas, the way of storing and
their contents in overall solids. Generally, solid waste is more
easily managed than waste in liquid form. Therefore, the avoidance
of adding water to non-liquid waste products is imperative. Also,
for the same reason, is the channeling of rainwater from roofs,
courtyards etc to waste management reservoirs. In the case when in
the unit relatively clean liquid waste is produced, it is
recommended that sluice is collected and stored separately from
animal waste, particularly when the animal waste products are not
liquid.
In the
case of solid waste (manure, bedding etc), heaps of dung are being
created and since the possibility of drainage of liquids from these
heaps exists, solid waste should be collected in waterproof,
concrete reservoirs. The manure and/or bedding that are devoid of
liquids can be stored in the ground, after, that is, provision is
made for the liquids to be drawn away from rainfall, through the
construction of a small canal in the perimeter of the heap. Solid
waste remains in the dung heap for an adequate time period so that
fermentation is completed.
In the
case of liquid waste, the following safeguards should be in place:
-
Limitation of loss of
nutrients,
-
Reduction
of organics in liquid waste,
-
Reliability
and simplicity of management method,
-
Lowest
possible cost of construction and maintenance of facilities.
The
management of liquid waste has to do mainly with pigsties, given
that in dairy farms and sheep farms the collection and storing of
liquid waste by washing should be avoided and that they are removed
timely as solid waste, with the use of scrapers.
The soil
is the only receiver of animal waste products, as it has a great
capability to turn to advantage their components, on condition that
there is proper application of waste products regarding the
quantities, the time and the way of application.
Therefore, the proper disposal of waste presupposes that:
·
They are not disposed of in
the soil during the rain season, particularly when the soil is in a
state of saturation or when it is frozen.
·
The disposal of crops should
be made at the right time through the application of chemical
fertilizers.
·
The area of disposal of
waste products should be located at a distance of at least 50 meters
from surface water, on condition that measures have been taken for
the prevention of surface effluence as well as the escape in ground
waters. Finally,
·
When it is carried out in
sloping ground, it must be made in such a quantity and in such a way
that effluence is avoided.
5.5 Waste per Livestock Unit Category
5.5.1 Sheep and Goat
Wastes
During
the breeding of goats and sheeps, the wastes are solid and they
remain in the bedding or under the rack for a long time in order to
ferment and be distributed to the crops. The collection of the
manure should not be carried out in ground channels, because its
removal from the channels to the collection tank should be done with
the addition of water. In case where the manure is not distributed
to the farmers soon, it should be stacked into the piles and block
the infiltration of rainwater from the midden to the ground.
5.5.2 Poultry Wastes
Poultry
wastes are separated into solid and semi-solid depending on the
breeding, in bedding or in cages. In case of bird fattening
breeding, the bedding removal takes place every
60
days. Afterwards, the bedding is stacked into piles till the
fermentation completion or it is distributed to farmers. Since the
pile is waterproof, a regional channel for the collection of the
liquids shedding, should be constructed. In the case of breeding of
chickens laying eggs in bedding, this is removed after the end of
the breeding; hence the fermentation lasts for 12-15 months and can
be distributed directly to the farmers. When breeding takes place in
cages without a dehumiditation system, the manure is semi-solid and
is removed either every day or within longer time periods (20-60
days), thus it should be placed in midden, where it remains for
natural drying or it is transported to manure processing locations.
In contemporary settlements providing manure ventilation and
dehumiditation system, it is taken out of the chamber in solid form
and it can be placed in a midden or be stirred 2-3 times in order to
accelerate the fermentation and composting process.
5.5.3 Cowsheds’ Wastes
The form
of the cows’ dung varies according to the type of stable.
During
the breeding in bedding or on manure bedding, dung remains in the
stable for some months.
There are no liquids,
because, either the straw used has absorbed them or they have been
evaporated. During the removal from the stable, the bedding has
already undergone a significant fermentation and it can be placed in
piles, without any danger of liquid run-off. For the avoidance of
rainwater run-off, the bedding should be placed on a waterproof
floor before its distribution to farmers.
In the
event that the wastes are in a semi-solid form or in the event that
the animals use the channels for this purpose, the wastes must be
managed in the same way as in the case of the liquid wastes.
5.5.4 Swine Wastes
Swine
wastes are usually liquid and must go through handling before
disposal. The disposal can be made either through direct absorption
in cultivated areas or in natural vegetation areas for fertilization
and soil enrichment with organic substances. The application of
liquid wastes should be made in such a way that sprawl and surface
run-off be eliminated and direct absorption will be favored. For
solid wastes a direct absorption is anticipated through tillage at
the right period. |
