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Indian J. Fert., Vol. 11 (12), pp. 46-51 (6 pages)
Enhancing Nutrient Use Efficiency through
Nano Technological Interventions
J.C. Tarafdar, Indira Rathore and Esther Thomas
ICAR-Central Arid Zone, Research Institute,
Jodhpur 342 003, Rajasthan
INTRODUCTION
Nanotechnology is the
revolutionary technology where
the particle size ranges between
1 and 100 nm at least in one
dimension. Due to their high
surface area and high reactivity
better penetration into the cell
these can activate plant and
microbial activities resulting in
more nutrient use efficiency.
Nanoparticles may trigger
enzymes and polysaccharide
release and act as effective
catalysts in plant and microbial
metabolism. These are commonly
referred to as a generic
technology that offers better
built, safer, long-testing, cost-
effective and smart products that
will find wide applications in
agriculture. Nanotechnology-
based products and their
applications in agriculture may
include nanonutrients, nano
pesticides, nanoscale carriers,
nanosensors, nano chips, nano
cellulose, nano barcode, quantum
dots, etc. Thus, fast growing
technology is already having a
significant commercial impact,
which will certainly increase
geometrically in the future.
Fertilisers have an axial role in
enhancing the food production in
developing countries especially
after the introduction of high
yielding and fertiliser responsive
crop varieties. In spite of this, it
is known that yields of many
crops have begun to decline or are
facing stagnation as a result of
Nanotechnology has the potential to revolutionize the agricultural systems by nanostructure formulation of fertilisers
which has mechanisms of targeted delivery or controlled release and conditional release, or could release their
active ingredients in responding to environmental triggers and biological demand more precisely. Nano-fertilisers
are the nano-particles-based fertilisers, where supply of the nutrients is made precisely for maximum plant growth
after stimulating the plant capability, have higher use efficiency, exploiting plant unavailable nutrients in the rhizosphere,
and can be delivered on real time basis into the rhizosphere or can be made available to plant by foliar spray.
Studies have shown that the use of nanofertiliser causes an increase in nutrients use efficiency, reduces the doses
of application dramatically and the frequency of the application along with the cost of the fertiliser. Hence,
nanotechnology has a great potential for achieving sustainable agriculture, especially in the developing countries.
imbalanced fertilisation and
decrease in soil organic matter
content. In the past few decades,
use efficiencies of N, P, and K
fertilisers have remained constant
as 30-35%, 15-20% and 35-40%,
respectively, leaving a major
portion of added fertilisers to
accumulate in the soil or enter
into aquatic system causing
eutrophication (1). In order to
address issues of low fertiliser
use efficiency, imbalanced
fertilisation, multi-nutrient
deficiencies and decline of soil
organic matter, it is indeed need
of the day to evolve the nano-
based fertiliser formulations with
multiple functions. Realizing that
the effective use of modern
technology is needed to improve
the nutrient use efficiency,
nanotechnology has a potential to
revolutionize the agricultural
systems.
Nanofertiliser technology is very
innovative and some of the
reports and patents strongly
suggest that there is a vast scope
for the formulation of the nano-
fertilisers. Significant increase in
yields has been observed due to
foliar application of nano-
particles as fertiliser (2,3).
Preliminary result suggests that
balanced fertilisation may be
achieved through nanotechnology
(4). Currently, the nitrogen use
efficiency is low due to the loss of
50-70% of the nitrogen supplied
in the form of conventional
fertilisers. New nutrient delivery
systems that exploit the porous
nanoscale parts of plants could
reduce nitrogen loss by promoting
enhanced plant N uptake.
Fertilisers encapsulated in
nanoparticles will increase the
uptake of nutrients (5). In the next
generation of nanofertilisers, the
release of the nutrients can be
triggered by an environmental
condition or simply released at
desired specific time. The present
paper discusses the nutrient use
efficiency enhancement through
nanotechnological interventions.
Nanonutrient Production
An essential feature for the
nanoparticle synthesis is the
preparation of the particles of
specific size and shape. For
agricultural use it is preferable to
have particle having size less
than 20 nm, polydispersity index
less than 1, zeta potential value
apart from +30mV and -30mV and
mostly cubed shaped particle to
enter through the plant pores (6).
Nanoparticles can be synthesized
by physical, chemical, physico-
chemical (aerosol) and biological
technique. Grinding, thermal
evaporation, sputtering and Pulse
Laser Deposition technique are
important physical methods.
Chemical synthesis, a very
powerful way of synthesis,
includes the technique like sol gel,
co-precipitation, microwave
synthesis, micro- encapsulation,
hydro thermal methods, polyvinyl
pyrolidene (PVP) method and
sonochemistry.
The aerosol method includes
Indian Journal of Fertilisers, December 2015
46
furnace method, flame method,
electro chemistry, CVD (chemical
vapour deposition) method PVD
(physical vapour deposition)
method. Biological methods offer
a safe and ecologically-sound
approach for nanoparticle
fabrication as an alternative for
physical, chemical, and aerosol
methods. The main advantages of
biological methods are that the
particles are usually encapsulated
by mother protein, therefore,
unless the protein layers break,
the particles are stable; so these
can be used for agricultural
purposes.
Figure 1 clearly demonstrates how
protein layer encapsulates each
and every nanoparticle.
There are various means of
biological synthesis of nano-
particles where selected microbial
proteins are used to break down
salts into their respective nano
forms. The biosynthesis of
nanoparticles may be possible
after using bacteria, fungi, plants,
biomolecules, herbs and
microwave-assisted biosynthesis.
Nutrient Use Efficiency
Improving nutrient use efficiency
(NUE) is a worthy goal and
fundamental challenge faced by
the fertiliser industry and
agriculture in general. The rise in
fertiliser prices, huge government
subsidy and stagnant crop prices,
exerted pressure on the
personnel concerned to improve
NUE. Most agricultural soils in
India have low native fertility and
successful and sustained crop
production on these soils requires
regular nutrient inputs. The
quantum of nutrients available for
recycling via crop residues and
animal manures is greatly
inadequate to compensate for the
amounts removed in crop
production. Thus, mineral
fertilisers have come to play a key
role in areas with low fertility
soils, where increased agricultural
production is required to meet
growing food demand. Chemical
fertilisers as source of plant
nutrients are considered as the
major contributor to enhance crop
production and maintaining soil
productivity.
Though the consumption of
chemical fertilisers in India
increased steadily over the years,
the use efficiency of nutrients
applied as fertilisers continues to
remain awfully low in specially P
(15-20%) and micronutrients (2-
5%) like zinc, iron, copper. When
nutrient inputs are used
inefficiently then both cost of
cultivation and threat of biosphere
pollution increase. Thus, the
economy and ecology highlights
the compulsive need for more
efficient use of nutrients in crop
production. Since, fertiliser
nutrients are expensive and used
in large quantities at national
level, any increase in use
efficiency will lead to a substantial
cut in nutrient requirement and
huge economic benefit at national
level.
Nutrient use efficiency may be
defined as yield per unit input. In
agriculture this is usually related
to the input of fertiliser, whereas
in scientific literature the NUE is
often expressed as fresh weight or
product yield per content of
nutrient. Improvement of NUE is
an essential pre-requisite for
expansion of crop production in
marginal lands with low
nutrient availability. NUE
depends not only on the ability of
crop plants to efficiently take up
the nutrients from the soil, but
also on transport, storage,
mobilization, uses within the
plant, and even on the
environment. Two major
approaches may be taken to
understand NUE. Firstly, the
response of plants to nutrient
deficiency stress can be explored
to identify processes affected by
such stress and those that may
serve to sustain growth at low
nutrient input. A second approach
makes use of natural or induced
genetic variation.
Tremendous improvement of NUE
was observed in plants after
application of nanoparticles. In
general, 3-4 times improvement in
use efficiency was noticed of P, Zn,
Fe and Mg nanoparticles. The effect
on P use efficiency is presented as
Figure 2.
The results clearly showed that
use efficiency of P can be
improved many folds when P is
applied as nanoform. Application
of Nano-P also helps in
improving the organic acid
concentration in the rhizosphere
and P uptake by the plants
(Table 1).
The use efficiency of the
micronutrients like zinc and iron
has improved many-fold with the
application as nano form (Table 2).
Response of nano-particles on root
Figure 1. Biosynthesis of protein encapsulated nano-particles
Indian Journal of Fertilisers, December 2015
47
growth and development was
studied under arid different
crops. The results showed effect
of nano-P on root growth
(improvement of root length up
to 32%, root area 20.6%, biomass
10.2%, root nodulation 67.7%).
Similar results were observed
with the application of nano Zn,
Fe, Mg where increase in root
length varied between 2-7%, root
area 4-18% and dry biomass 1-5%
while nodulation increased
between 3-47%. The Mg
nanoparticle application also
showed 19-21% more light
absorption on mungbean and
wheat.
Role of Nanoparticle in
Stimulation of Enzymes
Controlled foliar application of
nanoparticle can stimulate
different enzyme release (Figure 3)
by the plant to the rhizosphere
resulted in 12-243% more release
of beneficial enzymes such as
esterase, acid phosphatase,
alkaline phosphatase, phytase, aryl
sulphatase, nitrate reductase,
urease, cellulase, hemi cellulase,
lignase, after triggering different
co-factors inside the enzymes
(Table 3). Nanoparticles enter
though shoots (bark, cuticle,
stigma, stomata, hydothodes) and
roots (root tips, rhizodermis,
lateral root junctions and
wounding) of the plants.
Normally, more penetration was
found through stomata and
cuticle. After entering, the
nanoparticle moves through cell
sap. When such particles get
transported these trigger various
enzyme systems and most of
particles may agglomerate to
form mega particles on the
pathway and mostly get
deposited at the vacuole (Figure
4). At crop harvest no significant
differences, compared to control,
in nanoparticle concentration
were observed in leaves, stem
and seeds (Table 4). When full
scan TEM analysis was carried
out, it clearly indicated their
agglomeration as mega particle
with time and absorption in
different plant parts as a
nutrient.
Figure 2. Comparison of P use efficiency of single super phosphate (SSP),
soluble P (KH
2
PO
4
) and Nano-P
Table 1. Per cent improvement in organic acid concentration* in the
rhizosphere and P uptake by the plants
Crops Organic acid concentration P uptake
Clusterbean 23.2 27.2
Moth bean 19.5 23.5
Mung bean 20.7 22.7
Pearl millet 15.5 17.3
*Nano-P application @ 640 mg ha
-1
Table 2. Per cent use efficiency of Zn and Fe (average of four crops)
Micronutrient* Mega particle Nanoparticle
as fertiliser <20nm size
Zn 3.5 78.6
F e 4.6 81.2
*Doses of nano-Zn application 160 mg/ha and nano-Fe 480 mg/ha
Figure 3. Nanoparticle triggering co-factor of different enzymes
Indian Journal of Fertilisers, December 2015
48
Applications of Nano-nutrients
The nano-nutrients may be
applied by foliar mode on two-
week-old plants. It is better to use
aerosol sprayer for spraying of
nano-nutrients where the loss to
the environment is only 14.5% as
compared to 33% with normal
sprayer. The optimum doses of
application of some of the plant
nutrients have already been
standardized (for example P: 40
ppm, Fe: 30 ppm, Mg: 20 ppm, Zn:
10 ppm). The nanoparticles take
48-72 h time to enter into the
plants through leaf hole, therefore,
if there is any rain within 3 days
time repeat application is needed.
In general, nanoparticle size less
than 20 nm is the best for
penetration through foliar
application.
Nanotechnology has provided
the feasibility of exploiting
nanoscale or nanostructured
material as fertiliser carries or
controlled release vectors for
building of so-called “smart
fertiliser ” as new facilities to
enhance nutrient use efficiency
and reduce cost of environmental
protection (7,8). Encapsulation of
fertilisers within a nanoparticle is
one of these new facilities which
are done in three ways: (i)
Nutrient can be encapsulated
inside nanoporas materials, (ii)
coated with thin polymer film, or
(iii) delivered as particle or
emulsions of nanoscale
dimensions (9). In addition,
nanofertilisers will combine nano-
devices in order to synchronize
the release of fertiliser-N and-P
with their uptake by crops, thus
preventing undesirable nutrient
losses to soil, water and air via
direct internalisation by crops, and
avoiding the interaction of
nutrients with soil,
microorganisms, water and air
(10).
Coating and binding of nano
composites are able to regulate
the release of nutrients from the
fertiliser capsule (11). The
application of a nano-composite
consists of N, P, K, micronutrients,
mannose and amino acids
enhance the uptake of and use of
nutrients by grain crops (12).
Moreover, nanotechnology could
supply tools and mechanisms to
synchronize the nitrogen release
from fertilisers with crop
requirements. Studies have
shown that fertiliser
incorporation into cochleate
nanotubes (rolled-up lipid bilayer
sheets), improve the crop yields
(10). The advantage related to use
of nanotechnology in formulations
of conventional fertilisers are
presented as Table 5 (13).
Figure 4. Penetration, movement and accumulation of nano-particles in arid crops
Table 3. Increase in activity of beneficial enzymes with
nano-nutrients application
Beneficial Enzymes Per cent increase in activity
Dehydrogenanse 25-68
Esterase 23-90
Acid phosphatase 21-72
Alkaline phosphatase 18-136
Phytase 23-83
Nitrate reductase 12-47
Aryl sulphatase 19-68
Cellulase 48-243
Hemi-cellulase 37-115
Lignase 19-47
Table 4. Full scan TEM analysis data of accumulation of Zn (% atom) in
Zn nanoparticle treated plants in mung bean at crop harvest
Treatment Leaf Stem Seed
Control 1.13 2.93 0.91
Treated 1.20 2.98 1.14
LSD (p= 0.05) 0.08 0.11 0.25
Indian Journal of Fertilisers, December 2015
49
Nanostructure fertiliser exhibits
novel physico-chemical properties
which determine their interaction
with biological substances and
process. The application of
nanotechnological formulation to
agricultural crop inputs is one of
the proposed tools for
sustainable intensifications. These
applications include increased
uptake efficiency in plants,
developing DNA-based
nanosensor in polymer-coated
fertilisers which would release
only as much fertiliser as is
“demanded” by plant roots.
Nanofertiliser can delay the
release of the nutrients and extend
the fertiliser ’s effect period.
Nanomaterials may help to
improve nutrient use efficiency
because of their small size
(between 1 and 100 nm), more
surface area and their slow rate
of release, which facilitates the
plants to take up most of the
nutrients without any waste. It is
claimed that the controlled
nutrient release and increase in
water retention in the soil are
responsible for better yield
under nanofertiliser application.
Nano-sized TiO
2
promoted
photosynthesis (14) and nitrogen
metabolism (15), carbon nano-
tubes penetrate tomato seeds
and affect their growth rates.
Nano-functionalized carbon
nano-tubes enhance the root
elongation (16). Nano clay and
zeolites that are a group of
naturally occurring minerals
with a honey comb like layered
crystal structure, can be filled with
nitrogen, potassium, phosphorus,
calcium and a complete set of
minor and trace nutrients. This
helps to achieve better nutrient use
efficiency. Coating and bonding of
nano-and sub-nano composites are
able to regulate the release of
nutrients from the fertiliser
capsule (17) and the application of
a nano-composite consists of N, P,
K, micronutrients, mannose and
amino acids enhance the uptake
and use of nutrients by grain
crops. Fertilisers incorporated into
co-chleate nanotubes have been
shown to improve the crop yields
(10).
Cost of Cultivation
In general, it has been found that
the cost of cultivation due to
application of nanonutrients is
2-6 times less as compared to
application of chemical fertiliser
for equivalent yield of the crops. A
comparison of extra benefit
accruing with the application of
nano-P vis-a-vis chemical
fertiliser is presented in Table 6.
The results clearly indicate that
the application of Nano P is
accompanied by decline in cost of
cultivation and increase in
nutrient use efficiencies and crop
yields.
Ethical Issues
No adverse effect has been
observed so far with the
application of recommended doses
of nanoparticles on seed
germination, soluble seed protein
content, microbial diversity in the
rhizosphere, body weight and
consumption rate of mice,
nanoparticle concentration in
seeds at crop harvest, genetic
variability in plants.
Histopathology analysis was
performed. The liver, kidney and
spleen of control (Group A) and
test groups (Group B, C, D, E) were
fixed in 10% neutral buffered
formation for 120 hr and then
transferred finally to 70% ethanol
through 30% and 50% ethanol
gradients. The animal tissues were
processed using routine
Table 5. Some of the advantages related to transformed formulation of
conventional fertilisers using nanotechnology (10)
Desirable properties Examples of nanofertilisers-
enabled technologies
Controlled release formulations So called smart fertilisers might
become reality through transformed
formulation of conventional products
using nanotechnology. The nano-
structured formulation might permit
fertiliser intelligently control the
release speed of nutrients to match
the uptake pattern of crop.
Solubility and dispersion for Nano-sized formulation of mineral
mineral micronutrients micronutrients may improve solubility
and dispersion of insoluble nutrients
in soil, reduce soil absorption and
fixation and increase the
bioavailability.
Nutrient uptake efficiency Nano-structured formulation might
increase fertilisers efficiency and
uptake ratio of the soil nutrients in
crop production, and save fertiliser
resource.
Controlled release modes Both release rate and release pattern
of nutrients for water-soluble
fertilisers might be precisely
controlled through encapsulation in
envelope forms of semi-permeable
membranes coated by resin-polymer,
waxes and sulphur.
Effective duration of Nano-structured formulation can
nutrient release extend effective duration of nutrient
supply of fertilisers into soil
Loss rate of fertiliser nutrients Nanostructured formulation can
reduce loss rate of fertiliser nutrients
into soil by leaching and/or leaking
Indian Journal of Fertilisers, December 2015
50
histopathological techniques.
Histopathological analysis of
liver, kidney and spleen tissues
with the recommended doses of
nano P and nano Zn application
revealed that oral exposure of test
substances produced no
significant adverse effects as
evidenced by the normal tissue
architecture observed in the
exposed animals at post-
instillation time period of 90 days
in comparison to the normal diet
exposed controls. Overall analysis
of all the samples leads to the
conclusion that the gross
architecture was intact with no
noticeable or fibrosis within the
analyzed time (Table 7).
CONCLUSIONS
Nanotechnology has the potential
to revolutionize the fertiliser use
in agriculture. Nanotechnology
plays an important role in crop
nutrition. These mainly target the
co-factor of enzymes or at
cellular level and induce
physiological changes in crops
which ultimately results in terms
of better yield and more fertiliser
use. The salient findings of the
experiments clearly indicate the
usefulness and effectiveness of
nano-fertilisers to enhance the
growth and yield of the crop.
Nano-materials could preferably
be used for foliar application but
can also be used as seed
treatment or for soil application.
Nano-materials perform better
under lower concentration and
no adverse effect has so far been
noticed with recommended doses
of application. Overall
nanofertilisers can enhance the
nutrient use efficiency and
improve soil fertility in an eco-
friendly manner.
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Table 6. A comparison of cost of cultivation of Nano P with SSP and DAP
for pearl millet
Fertiliser Cost of cultivation (Rs./ha) Yield status (kg/ha)
(Rate of application)
SSP (80 kg/ha) 640 950
DAP (80 kg/ha) 2000 963
Nano P (720 mg/ha) 352 1093
LSD (p:0.05) - 37
Table 7. Summary of histopathological analysis for estimating toxicological
effect of test substance (-ve indicates no toxicity observed)
Tissue/Groups Group A Group B Group C Group D
Liver -ve -ve -ve -ve
Kidney -ve -ve -ve -ve
Spleen -ve -ve -ve -ve
Indian Journal of Fertilisers, December 2015
51
