Modern concepts of fertilizer evaluation involve direct and indirect methods. Direct methods use isotope techniques to discriminate between nutrient uptake from fertilizer versus soil. Indirect methods compare fertilizer treatments to an unfertilized control or standard fertilizer response curve. Both have limitations, as yield response does not always correlate with nutrient supply and replications cannot eliminate all variability. New nanofertilizer technologies aim to minimize chemical use while meeting crop nutritional needs.

1. MODERN CONCEPT OF FERTILIZER
EVALUATION
Presented by
Ramnath Potai
Ph.D. Scholar
Dept. of Agronomy
Indira Gandhi Krishi Vishwavidyalaya, Raipur

2. Fertilizer evaluation
• The ability of a particular material to supply nutrient to a
plants depends not only on the chemical characteristics of the
material itself but also on the species grown and the conditions
of the plant growth.
• Until recently the evaluation of fertilizers was based only on
the yield response or on increased uptake of particular nutrient
by the plant.
• Unfortunately, yield response and nutrient uptake often
interact with both the level of other nutrients and other
environmental factors that effect plant growth.

3. Why fertilizer evaluation?
(a) Determining the fertilizer needs of specific crops
and soils;
(b)Achieving reliable and economic fertilizer
recommendations, that is, ensuring that right
types and quantities of fertilizers are applied;
(c) Checking wastage of fertilizers; and
(d) Minimizing soil and water pollution through the
addition of excessive amounts of chemical
fertilizers.
• Although fertilizer evaluation is a powerful tool
to support high productivity by way of
rationalizing nutrient use, its current impact on
farm practice is presently not visible. In order to
make it an effective and farmer oriented service.

4. 1. Direct methods
• By means of isotope techniques it is possible to discriminate
directly between that quantity of element in the plant derived
from the fertilizer and the quantity of fertilizer derived from
the soil. There are essentially two ways of utilizing this
information to rate quantitatively the ability of two materials to
supply nutrient to the plant , namely, calculation of per cent
utilization of applied nutrient and calculation of the per cent of
the total element in the plant derived from the fertilizers.
• Note- isotope is one of two or more species of atoms of a
chemical element with the same atomic number and position in
the periodic table and nearly identical chemical behaviour but
with different atomic masses and physical properties.

5. Isotope of N,P,K.
• Ordinary potassium is composed of three isotopes, K-39, -40,
and -41.
• Nitrogen has two stable isotopes, N-14 and -15
• Phosphorus (P) has 23 known isotopes with a mass number
ranging from 24 to 46. Only one is stable, P-31, making
phosphorus a mono isotopic element. Longer-lived phosphorus
radioisotopes are phosphorus 33 (P-33) (half-life of 25.34
days) and phosphorus 32 (P-32) (14.263 days)

6. A. Per cent utilization of applied nutrient
• The per cent utilization of applied nutrient is a direct
comparison between amount of nutrient taken up from the
fertilizer and amount of nutrient applied. Thus, if the
amount of nutrient applied in the form of two different
fertilizers is B and D and the amount of nutrient taken up
from each source is Mb and Md, then the per cent
utilization of B, Ub, and D, Ud are shown in equation.
Ub = Mb / B *100
Ud = Md / D* 100
• Then the relative rating of the two materials is:
• Ub / Ud = Mb / B ÷ Md / D = Mb / Md × D/B

7. • Equation Provided the relationship between nutrient supply
and per cent utilization is linear. This relationship, however is
not linear but parabolic and only approaches linearity at a low
per cent utilization. A low per cent utilization is normally
obtained when the soil is high in the nutrient in question. In
practice, the rate of application of the two nutrients, B and D,
is chosen at the same level and the per cent utilization is then
compared.

8. • Another difficulty in using per cent utilization is that the
addition of the fertilizer itself may result in a yield response
and an overall increase in the uptake of nutrient not only from
the soil but also from the fertilizer. Thus, the increase in the
percent utilization of a given material may be confounded by
an increase in growth resulting in further uptake from the
added fertilizer material.
• Only when there is no physiological response to the applied
fertilizer can this difficulty be overcome. Nevertheless, percent
utilization of applied fertilizer is a direct measure of fertilizer
efficiency under a given set of conditions. This direct measure
of amount of, or per cent of, the fertilizer nutrient utilized
cannot effectively be performed in any other way.

9. B. Percent of the total element in the plant derived
from the fertilizer
• When a nutrient element, M, in the fertilizer is labelled with
an isotope of the element, M1, which may be either a stable
or radioisotope, the fraction of M in the plant derived from
the fertilizer, Fm, is found as the ratio of the specific
activities of the element in the plant and in the fertilizers,
i.e.,
• Fm = M1(plant)/ M(plant) ÷ M1 (fertilizer)/ M (fertilizer)
• Where M is the amount of a given unlabelled nutrient ion;
M1, amount of a given labeled nutrient ion; and Fm, the
fraction of the nutrient ion in the plant derived from the
fertilizer. Fm can be expressed as the percent of the nutrient
ion in the plant derived from the fertilizer by simply
multiplying by 100.

10. C) Additional methods
i) Competitive ions as tracers.
• Unfortunately, suitable isotopes of each of the nutrients elements do
not exist. This has suggested the use of competitive ions as tracers.
Of the known competitive ions the nutrients without suitable tracers
the competition of Rb and K is the most important. There is no
suitable isotope of k for use in labeling fertilizers. Potassium 42
(t1/2 = 12.5 hours) and K43 (t1/2 = 22 hours) have too short a half-
life to be of practical value in pot or field experiments that usually
last from several weeks to months. Enrichment of the natural
radioisotope of K, K40, or enrichment of the stable isotope K41 are
so expensive at present as to be prohibitive in cost.
• Since Rb are K are indisținguishable insofar as ion uptake is
concerned, Rb has been tested as a tracer of K in soil studies. The
result of the classic experiment which compared the use of Rb as a
tracer to a true tracer of K, namely K41.

11. • The results illustrate that when Rb data are used to calculate
the per cent K in the plant derived from added K, completely
erroneous results are obtained. Not only is the magnitude of
the results in error, but the soils are not even rated in the same
order. Thus, the plant may not be able to distinguish between
K and Rb insofar as the uptake process is concerned, but the
distinction is made in the soil. As far as distribution in the
plant is concerned, K:Rb ratio can vary (Mackie and Fried,
1955).
• The distribution factor, i.e., the ratio of Rb/K in the plant to
Rb/K in the soil, is constant for given soil-plant system, but
differs from soil to soil. This means that Rb can be utilized as a
tracer for K in a given soil with respect to kind, time of
application, or placement with valid results. It is not valid,
however, to make a comparison among soils or to attach
particular significance to the absolute magnitude of Rb uptake.

12. Effect of soil type and added K on the distribution factor (D.F.) for Rb uptake
Soil type Level of added K (lb K2O/ acre)
10 50
Decatur
Davidson
Grenada
Wooster
Herrick
Hagerstown
0.24
0.25
0.30
0.35
0.43
0.46
0.26
0.25
0.31
0.34
0.38
0.45
*D.F. - Rb/K (plant) ÷ Rb/K (soil). From Fried and Hawkes (1959)

13. ii) Commercial Materials:-
• It is essential that any comparison with labeled fertilizers or,
for that matter, with any fertilizers, be done with materials that
reasonably well simulate the commercial product. This is no
particular problem with non labeled fertilizers as the
commercial product can be used directly, Laboratory
preparations of labeled fertilizers,
• however, will seldom be the same as the commercial product
unless a special effort is made. This was illustrated by a
comparison of a series of nitric phosphate fertilizers containing
different amounts of water-soluble P. The entire series of
materials was made in two ways, resulting in two sets of
materials with identical water and citrate solubilities. A plant
test in the greenhouse, however, indicated that the effect of
method of preparation was very great and, in fact, much
greater than the effect of water solubility
(Hawkes and Fried, 1957).

14. Effect of tracer used on the calculation of percentage of added
K in the plant derived from the fertilizer (Fried & Heald)
Isotope used
Soil type K41 (%) Rb86 (%)
Decatur
Davidson
Grenada
Wooster
Herrick.
Hagerstown
19
12
15
18
13
13
4.8
3.1
4.5
6.1
5.0
5.9

15. iii) Natural Product
• Generally, process materials can be labeled, provided suitable
isotopes are available. Natural products cannot be labeled
because any treatment of the fertilizer will drastically change
the chemical characteristics of the fertilizer and its interaction
with soil (Fried, 1954).
• To overcome this, Fried and MacKenzie (1949) irradiated rock
phosphate directly in a neutron pile and attempted an
evaluation in soil. This was later shown to be invalid, owing to
the recoil effect on P atoms that absorbed the neutrons,
resulting in the presence of labeled non-orthophosphate P
(Fried and MacKenzie, 1950; Mac- Kenzie and-Borland,
1952).
• Natural products, however, can be compared with each other
or other sources by comparing each against a standard source.
The residual supply of P from past fertilizer treatments can be
measured in the same way.

16. • The evaluation is based on the thesis that A value are quantitative measures
that can be added and subtracted since they are measures of the amount of
available nutrient in terms of some standard unit of measure. The technique
involves determining the A value of the soil alone while, at the one time,
determining the A value of the soil plus the residual material or the natural
fertilizer. As long as the same standard is used, the two A values may be
subtracted from each other. The calculations are shown below:
• A1 = B1(1 – Fm1)/Fm1 (1)
• A1+ A2 = B1(1- Fm2)/Fm2 (2)
• Where A1 is the amount of available nutrient in the soil, A2 is the amount of
available nutrient in the natural fertilizer material or residual material); B1,
amount of nutrient applied as standard, Fm1 and Fm2 proportion of the
nutrient in the plant derived from the standard Subtracting
• Eq. (1) from Eq. (2)
• (A1 + A2) – A1 = A2 = B1/Fm2 – B1/Fm1 (3)

17. • (3) equation gives the amount of available nutrient in the
applied natural fertilizer (or residual material) in terms of the
standard.
• If B2, is the total amount of nutrients in the applied natural
fertilizer, than A1,/B2, is the relative amount of each material
(standard and natural product) needed to supply the same
amount of plant available nutrient. The relative efficiency of
the two materials is the inverse of this ratio.
• The results are essentially identical to those obtained under
Additional methods since the property of the ability to add and
subtract A values is utilized to obtain a relationship that can be
obtained directly when materials can be directly labeled. Thus,
any number of materials may be compared or residual values
of applied materials determined.

18. For instance
• From an agronomic standpoint, the evaluation of fertilizer
requires knowledge of the ratio of the amounts of each
fertilizer that will supply the same amount of plant available
nutrient.
• When a fertilizer such as superphosphate is added to the soil
two sources of phosphorus are present in the growth medium-
soil phosphorus and fertilizer phosphorus.
• The percentage of the total phosphorus derived from the
fertilizer will depend on the plant-available amounts of both
soil phosphorus and fertilizer phosphorus.
• If the amount of fertilizer phosphorus added is increased, the
percentage of phosphorus in the plant derived from the
fertilizer will increased and that from the soil will decreased.

19. • The quantitative estimate of the relative efficiency of fertilizer
materials can be made by an extension of the technique
involving radioactive labeled fertilizers.
• For the purpose of describing the proposed method, fertilizers
are divided into two groups;
 Processed fertilizer- e.g., superphosphates and nitrophosphates
and
 Natural produces- rock phosphates, bone meals.
• As the half life of an isotope places a practical limit on the
limit on the direct determination of uptake from the fertilizer,
the residual value of applied phosphates is included with the
natural products.

20. 2. INDIRECT METHODS
• The rating of fertilizer using the indirect method
involves comparison of particular fertilizer treatments
with a control in which no fertilizer has been applied. A
more sophisticated method involves as a control
enough different rates of application of a standard
material that the whole response curve is determined.
The yield of dry matter or nutrient obtained with the
fertilizer material tested is then located on this standard
curve and the equivalent amount of standard read off
the abscissa. Where isotopes are not available, this is
the method of choice and has been used by various
investigators (Terman et al., 1962, Armiger and Fried,
1957, 1958: Black and Scott, 1956, White and
Kempthorne, 1956)

21. • There are certain inherent difficulties in the use of yield
response or yield of nutrient to determine the efficiency of
applied fertilizers. If the plant is provided with a nutrient
element from two materials, A and B, in which B when applied
at the same rate as A will supply Twice as much nutrient to the
plant, there are three possibilities in yield response
comparisons of the two materials:
• (1) No yield response, because the nutrient level in the soil
was already so high or because other factors of nutrition,
temperature, moisture, disease, or insect pests limited yield;
• (2) slight yield response to both materials because the yield
level is close to the maximum for the conditions of the
experiment; and
• (3) marked yield response to both materials with a slight
difference between them.

22. • In theory, quantitative evaluation in valid only when the check yield and both
treatment yields are on the linear response part of the curve that is between zero
yield and below Yc. In practice, this requires the use of a soil almost devoid of the
nutrient and a comparison as yield levels that are not usually found in agricultural
practice.

23. • Terman et al. 1962, list a number of practices that may reduce
the experimental errors in fertilizer source-evaluation
experiments in the field. These practices include
• proper selection of experimental sites
• adequate number of replication,
• uniform preparation and application of fertilizers,
• control of limiting yield factors,
• and sampling and harvesting techniques.
• There is still a fundamental difficulty, however, in
quantitatively evaluating fertilizer materials. Replications in
the field cannot be increased ad infinitum, nor is it valid to
make tests only on the homogeneous soil situations which tend
to occur only on relatively level areas of similar microclimate.
No amount of statistics can substitute for the basic difficulties
in the method of fertilizer evaluation.

24. Fertilizer application
• Fertilizers play a vital role in increasing agricultural production, but
excessive use of chemical fertilizers irreversibly damages the
chemical ecology of soil and reduces the available area for crop
production.
• Sustainable agriculture demands minimal use of agrochemicals.
Advanced nanoengineering techniques are being used to overcome
an agricultural crisis by developing an improved crop production
system that assures sustainability.
• Global food security is under serious threat across the world
because of the limited availability of natural resources such as fertile
land, quality seeds, and water. It has been estimated that the world
population (currently 7.8 billion people) will increase to
approximately nine billion by 2050. Global agricultural systems are
facing numerous unprecedented challenges, including rapid climatic
changes.

25. • The global agricultural landscape has radically changed since
the revolution of green nanotechnology. Nano fertilizers are
now being used in specific concentrations, in accordance with
the nutritional requirements of the crops, ensuring minimal
differential losses.
• There are three types of nano fertilizers: nanoscale fertilizers,
nanoscale additive fertilizers, and nanoscale coating fertilizers.
• Nanoscale fertilizers are made of nanoparticles that contain
nutrients. Nanoscale additive fertilizers are traditional
fertilizers with nanoscale additives. Nanoscale coating
fertilizers are traditional fertilizers coated or loaded with
nanoparticles.
Nano Fertilizers

26. • The encapsulation of nutrients most commonly produces nano
fertilizers with nanomaterials. Preliminary nanomaterials are
produced by using both physical (top-down) and chemical
(bottom-up) approaches.
• More recently, the targeted nutrients are either encapsulated
inside nanoporous materials, coated with a thin polymer film
particle, or coated with emulsions of nanoscale dimension.
• Encapsulation of beneficial microorganisms, such as bacteria
or fungi, has shown promise as it can enhance the availability
of nitrogen, phosphorus, and potassium in the root zone,
thereby improving plant growth. Porous nanomaterials
significantly reduce nitrogen loss by regulating demand-based
release, and by enhancing the plant uptake process.

27. • Nanofertilizers can also be classified based on their actions:
control or slow-release fertilizers; control loss fertilizers;
magnetic fertilizers or nanocomposite fertilizers (which use a
nanodevice to supply a wide range of macronutrient and
micronutrients in desirable concentration).
• Examples of porous nanomaterials include:
• Ammonium charged zeolites, which can enhance the solubility
of phosphate minerals, showing an improvement in
phosphorus availability and uptake by crops.

28. • Graphene oxide films, a carbon-based nanomaterial, can
prolong potassium nitrate release, extending the time of
function and minimizing losses by leaching.
• Nanocalcite (CaCO3-40%) with nano SiO2 (4%), MgO (1%),
and Fe2O3 (1%) which not only improve the uptake of
calcium, magnesium and iron, but also notably enhance the
intake of phosphorous with micronutrients zinc and
manganese.