CRF products are three times more expensive than traditional fertilizers (Suppan 2017). This is better than soluble
fertilizers because it promotes fertilizer rationalization and
while maximizing plant uptake, minimizes its wastage and
unintentional release into the environment. CRFs can also be
engineered to release their contents in response to particular
environmental or plant physiological triggers (Qureshi et al.
2018). Nano-fertilizers have greater nutrient use efficiency,
due to a much greater surface area-to-volume or mass ratio;
therefore, they are more reactive and thus required in lesser
amounts. Nano-fertilizers having particulate size less than
the pore size can also be uptaken by the plant roots or leaves
via soil application and foliar spray, respectively (Qureshi
et al. 2018). Nano-fertilizers can be made to form colloidal
suspensions, if the nutrient required has low solubility.
4 Engineered Nanoparticles-Based
Nano-pesticides
4.1 Necessity and Limitations of Conventional
Pesticides
Pest is usually defined as any animal or plant which is
detrimental to human interests, in this case decreasing the
productivity of agriculture. They belong to a spectrum of
phylum from nematodes, mollusks, arthropods to other
plants. These damage crops via direct biomass consumption,
root nutrient assimilation or competition for light and water
resources. Pests have been around since the advent of agriculture. It has been estimated that a third of all crops are
produced globally using pesticides annually. Pests cause the
loss of 18% of all crops globally, without the use of pesticides huge losses in production of fruits, vegetables and
cereals occur (Oerke 2006; Zhang 2018). The first recorded
countermeasure, pesticide, being dusting of elemental sulphur on crops in ancient Sumer around 4500 years ago,
followed by the Rig Veda mentioning the extracts of certain
poisonous plants, could be used as pesticides around
4000 years ago (Pandya 2018). In the fifteenth century,
certain heavy metals such as mercury, arsenic and lead were
used to kill pests, while two new natural pesticides pyrethrum and rotenone were introduced in nineteenth century,
which were derived from chrysanthemums and roots of
tropical vegetables, respectively (Hussaini et al. 2013). The
discovery of organochlorides such as DDT was a landmark
event and it was used extensively since the 1940s both as a
pesticide and a disease vector control. However, in the light
of its ecotoxicity, DDT had been phased out by the Stockholm Convention in 2001, on persistent organic pollutants
(POP) for agricultural applications, followed by another
notorious pesticide, endosulfan in the year 2011.
The problems concerning pesticides and need to develop
new pesticides can be better understood, if one studies it
from an agroecological point of view. Agricultural fields are
artificially selected monocultures of a single species which
has been bred or even genetically modified to overexpress a
trait which is of economic value to humans. However, these
crop fields, although created and maintained by humans, are
not isolated from the ecosystem. The pests which continue to
feed on the crops are also subject to the same directional
evolutionary pressures and are forced to evolve along those
lines to ensure survival. The application of pesticides to
minimize crop loss only adds to the directional evolutionary
forces added on the pests to evolve and adapt.
The second problem in the use and often overuse of
pesticides is the unintentional poisoning of the environment
and ultimately humans. The average annual global consumption of pesticides stands at 2 million tons, with 3 kg
ha
−1 applied (Devi et al. 2017). It has been estimated that
around 3,55,000 people die annually due to overexposure to
pesticides (Carvalho 2017). Pesticides are applied on crops
in powder, solution or emulsion form where they can be
blown off or become volatilized into the atmosphere in a few
days, which can lead to a major loss of the applied amount
(Aktar et al. 2009). Pesticides can also be leached from the
cropland into aquatic bodies. As a general rule, area of
unintentional deposition of the pesticide will depend on its
volatility. Non-biodegradable synthetic pesticides can persist
in the environment for weeks to years and thus classed under
persistent organic pollutants (POPs). Figure 3 is a simple
representation of the pathway taken by pesticides across
ecosystems and trophic levels.
Pesticides achieve pest suppression in several ways, some
of the most popular being hormone and neural disruption.
However, unintentional targets bearing similar physiology
and biochemistry also suffer the ill effects such as bees,
shrimps and crabs. The target pest can also be assimilated
within the food web, leading to the accumulation of pesticides in subsequently higher trophic levels, and this phenomenon is called as “biological magnification”. Overuse of
pesticides can also cause detriment to soil microecosystem,
which is responsible for the long-term fixing of nutrients in
the soil (Aktar et al. 2009). Ultimately, pesticide residues can
make their way through the food web to humans, where they
have been associated with diseases such as endocrine disruption, obesity and cancer (Caravalho 2017). Firstgeneration organochloride pesticides were especially persistent, because of this reason and development of pest
resistance urged their replacement by organophosphates,
which are less persistent in the environment (Caravalho
2017). One often overlooked aspect during pesticides discussion is about required allied chemicals. Many pesticides
are lipophilic, hence need solvents for dispersing in water.
158
N. Sarkar et al.
fertilizers because it promotes fertilizer rationalization and
while maximizing plant uptake, minimizes its wastage and
unintentional release into the environment. CRFs can also be
engineered to release their contents in response to particular
environmental or plant physiological triggers (Qureshi et al.
2018). Nano-fertilizers have greater nutrient use efficiency,
due to a much greater surface area-to-volume or mass ratio;
therefore, they are more reactive and thus required in lesser
amounts. Nano-fertilizers having particulate size less than
the pore size can also be uptaken by the plant roots or leaves
via soil application and foliar spray, respectively (Qureshi
et al. 2018). Nano-fertilizers can be made to form colloidal
suspensions, if the nutrient required has low solubility.
4 Engineered Nanoparticles-Based
Nano-pesticides
4.1 Necessity and Limitations of Conventional
Pesticides
Pest is usually defined as any animal or plant which is
detrimental to human interests, in this case decreasing the
productivity of agriculture. They belong to a spectrum of
phylum from nematodes, mollusks, arthropods to other
plants. These damage crops via direct biomass consumption,
root nutrient assimilation or competition for light and water
resources. Pests have been around since the advent of agriculture. It has been estimated that a third of all crops are
produced globally using pesticides annually. Pests cause the
loss of 18% of all crops globally, without the use of pesticides huge losses in production of fruits, vegetables and
cereals occur (Oerke 2006; Zhang 2018). The first recorded
countermeasure, pesticide, being dusting of elemental sulphur on crops in ancient Sumer around 4500 years ago,
followed by the Rig Veda mentioning the extracts of certain
poisonous plants, could be used as pesticides around
4000 years ago (Pandya 2018). In the fifteenth century,
certain heavy metals such as mercury, arsenic and lead were
used to kill pests, while two new natural pesticides pyrethrum and rotenone were introduced in nineteenth century,
which were derived from chrysanthemums and roots of
tropical vegetables, respectively (Hussaini et al. 2013). The
discovery of organochlorides such as DDT was a landmark
event and it was used extensively since the 1940s both as a
pesticide and a disease vector control. However, in the light
of its ecotoxicity, DDT had been phased out by the Stockholm Convention in 2001, on persistent organic pollutants
(POP) for agricultural applications, followed by another
notorious pesticide, endosulfan in the year 2011.
The problems concerning pesticides and need to develop
new pesticides can be better understood, if one studies it
from an agroecological point of view. Agricultural fields are
artificially selected monocultures of a single species which
has been bred or even genetically modified to overexpress a
trait which is of economic value to humans. However, these
crop fields, although created and maintained by humans, are
not isolated from the ecosystem. The pests which continue to
feed on the crops are also subject to the same directional
evolutionary pressures and are forced to evolve along those
lines to ensure survival. The application of pesticides to
minimize crop loss only adds to the directional evolutionary
forces added on the pests to evolve and adapt.
The second problem in the use and often overuse of
pesticides is the unintentional poisoning of the environment
and ultimately humans. The average annual global consumption of pesticides stands at 2 million tons, with 3 kg
ha
−1 applied (Devi et al. 2017). It has been estimated that
around 3,55,000 people die annually due to overexposure to
pesticides (Carvalho 2017). Pesticides are applied on crops
in powder, solution or emulsion form where they can be
blown off or become volatilized into the atmosphere in a few
days, which can lead to a major loss of the applied amount
(Aktar et al. 2009). Pesticides can also be leached from the
cropland into aquatic bodies. As a general rule, area of
unintentional deposition of the pesticide will depend on its
volatility. Non-biodegradable synthetic pesticides can persist
in the environment for weeks to years and thus classed under
persistent organic pollutants (POPs). Figure 3 is a simple
representation of the pathway taken by pesticides across
ecosystems and trophic levels.
Pesticides achieve pest suppression in several ways, some
of the most popular being hormone and neural disruption.
However, unintentional targets bearing similar physiology
and biochemistry also suffer the ill effects such as bees,
shrimps and crabs. The target pest can also be assimilated
within the food web, leading to the accumulation of pesticides in subsequently higher trophic levels, and this phenomenon is called as “biological magnification”. Overuse of
pesticides can also cause detriment to soil microecosystem,
which is responsible for the long-term fixing of nutrients in
the soil (Aktar et al. 2009). Ultimately, pesticide residues can
make their way through the food web to humans, where they
have been associated with diseases such as endocrine disruption, obesity and cancer (Caravalho 2017). Firstgeneration organochloride pesticides were especially persistent, because of this reason and development of pest
resistance urged their replacement by organophosphates,
which are less persistent in the environment (Caravalho
2017). One often overlooked aspect during pesticides discussion is about required allied chemicals. Many pesticides
are lipophilic, hence need solvents for dispersing in water.
158
N. Sarkar et al.