Isotope use in agriculture

2. Course seminar
on
Isotopes and its uses
in soil and plant
studies
Advisor Speaker
Dr Ramawatar Meena Priyal pandey
I.D No-S-11156

3. CONTENT
Introduction
Brief history and units of isotope
Monitoring instruments
Use of isotopes in soil and plant studies
Future areas of research

4. Introduction
Atom
Indivisible part of matter
Very small nucleus
Proton
Neutron
Electron

5. Nuclear symbol
Atomic
number
Element
symbol
Valency
Atomic
mass
Atomic number
== =P E
P N
Atomic
mass

6. Isotone Isobars Isotope
Different
Different
Same
Different
Same
Different
Same
Different
Different
Atomic
number
Atomic
Mass
Neutron

7. 56
27C
56
24Cr
56
25Mn
56
26Fe 2 He3
1 H2
Isotope IsotoneIsobar

8. Isotope
Isotopes are atoms of same
element having same atomic
number but different mass
number.
Classification
Stable isotope- No
disintegration ,no radioactivity.
Unstable isotope-Radioactivity,
disintegration into alpha, beta,
gamma radiation.

9. Disintegration of unstable
isotope

10. History and unit of
radioactivity
Henri Becquerel-phenomenon of radio activity(1896).
Madame curie – coined word radio activity.
G. de Hevesy-isotope tracer technique(used lead isotope as a
tracer of lead uptake by plant).
Unit of radio activity
1 rd-1x106 disintegration per second.
1 curie=3.7 x10 rd
1 Becquerel=1 d.p.s

11. Some basic terms
Radioactivity-it is a phenomenon in which nuclei under
goes disintegration with emission of α or β particles.
Half life-the time required for a given amount of a radio
element to decay to one half of its initial value.

12. Radioactive tracers
When small amount of radio isotope is used to trace or
follow a biological or a chemical process ,it is called radio
active tracer.
Carrier free
Carrier
Tagged compound

13. Monitoring instruments
Geiger Muller
counter
Liquid scintillation
counter
Mass
spectrophotometer
Autoradiography
Gamma counter

14. Geiger Muller counter
coated with Ag or graphite “cathode”
Tungsten (W) wire “anode”
Ar0  Ar+ + e-
insulator
Ar+ Ar+ Ar+
e- e- e-
beta

15. Scintillation
counter
Discovered by Kallman and
Reynold (1950).
Best method to count β
particles.
Solid scintillation counter.
Liquid scintillation counter.

16. Mass spectrophotometer
An analytical technique in
which atom and molecule from
sample are ionized separated
according to their mass and
charge ratio (m/z) and then
recorded.
Also called isotope ratio mass
spectrophotometer.
The isotope has to be converted
to gas(N2 ,SO2, CO2, H2) by
means of suitable preparation
system.
This gas is fed into mass
spectrophotometer where ratio of
the isotopes of interest are
determined..

17. Gamma counter
Gamma rays are not charged
particles and are not deflected in
electric and magnetic field.
Gamma counter has 2 detector
element ,a sodium iodide crystal and
a photomultiplier.
Soil and liquid sample can be
counted.
Sample is introduced in counter
and is brought alongside sodium
iodide crystal and photomultiplier
and gamma rays emitted from
sample are counted.

18. Autoradiography
Discovered by Becquerel
(1896).
Used to trace movement
of radio active material in
biological system.

19. Element Isotope stability Half life Uses
Oxygen 18O Stable ----- Hydrology
study,
photosynthesis
Hydrogen 3H , 2H Radioactive
,Stable
12.43 year Water
movement,
water cycling
carbon 13C , 14C Stable
,Radioactive
5370 year Soil organic
matter studies,
soil salinization,
photosynthesis
Cesium 137Cs Radioactive 30 years Soil erosion
study
Cobalt 60Co Radioactive 5.3 year Soil aggregation
study
Chlorine 36Cl Radioactive 301000 years Solute
movement
study
chromium 51Cr Radioactive 27.8 days Sewage study
Calcium 45Ca Radioactive 165 days Soil Ca , plant
Ca movement

20. Element Isotopes stability Half life Uses
Nitrogen 15N Stable - Fertilizer N uses
efficiency,
nitrogen fixation,
nitrogen balance,
N transformation
in soil
Phosphorus 32P ,33P Radioactive 14.3days,25
days
Fertilizer P use
efficiency ,root
pattern of crop,
evaluation of rock
phosphate,
Diffusion in soil
,Root
autoradiography
Sulphur 34S , 35S Stable
,Radioactive
81.7 days Environmental
pollution , sulphur
cycling
IAEA bulletin 1999

21. Use of isotopes in soil and
plant system
In field of soil chemistry and
Soil physics
In field of soil quality
degradation related problem
Plant and nutrition In field of fertilizer uses
Isotope
uses

22. Ground water tracers
Age of water; tritium an active water tracer.
Carbon14 is used to determine age of older ground
water.
Direction and flow of natural ground water- 3H and
131I.
Depth of availability of water- 3H.
Water movement study- 2H.
Bhism kumar 2005

23. Various recharge estimation
techniques (summarized after
Scanlon et al., 2002)
Technique Tracer
Technique based on surface water Isotopic tracer 18O and 2H
Technique based on unsaturated zone
Applied tracers (3H, Bromide, dye)
Historical tracers (3H, 36Cl)
Environmental tracers (Chloride
method )
Techniques based on saturated zone
Historical tracers (3H, 3H/ 3He)
Environmental tracers (Cl, 14C)
Isotopic tracers (18O and 2H)

24. Sources of nitrate ground
water
Isotopic signature of different nitrate sources (Kendall ,2000)
Nitrogen retention and transport in soil

25. Carbon Isotopes in Investigations
Related to SOC and Soil Quality
in Agroecosystems
Issues References
Impacts of land-use changes (C3 and C4
plants) on SOC sequestration in
agricultural soils in northern Italy
Del Galdo et al. 2003
Impacts of conventional or zero tillage on
changes in soil nitrogen and carbon stocks
in southern Brazil
Sisti et al. 2004
Relative contribution of vegetation types
(C3 trees and C4 crops) to soil carbon
reserves in West Africa savannah
Traore et al. 2004; Bayala et al. 2006
SOM pools and 13C signatures in particle
size fractions of a long-term agricultural
field experiment receiving organic
amendments
Gerzabek et al. 2001

26. (Bayala et al., 2006)

27. Presence of humic molecules
in soil

28. Use of isotopes in organic
residue study
N recovery by organic sources is< than 20%.
To optimize the potential N benefit of organic input. it is
necessary to be able to predict the amount of N supplied to
the crop from organic input.
Use of 15N in organic fertilizer studies has advance
understanding of N release from organic material.

29. Available phosphorus-A
value concept
A value concept was given by Fried and Dean (1952).
When plant is confronted with 2 sources of given
nutrient, the plant will absorb from each of this in
proportion to respective amount available.
The amount of available nutrient in soil to be
determined in term of fertilizer standard is known as A
value
A= B (1-Y)/Y where A is amount of available nutrient
in soil , B is amount of applied fertilizer nutrient ,Y is
proportion of nutrient derived from fertilizer nutrient

30. Stable isotope technique to
study soil Salinization
Soil salinization
Vegetative
degradation
§ 13C Value of
soil carbonate
Increasing
salinity
decreasing
organic
matter
Carbon fractionation
YongQuin CUI 2011

31. Isotopic Techniques in Greenhouse Gas
(GHG) Studies
GHG Isotopic technique Experimental work References
N2O Natural abundance
(15N and 18O isotopic
signatures)
Soil microbial
processes affecting
nitrous oxide (N2O)
emissions and
factors influencing
nitrification and
denitrification in
tropical Amazon
rain forest soils
Perez et al.
2003
CO2 Natural abundance
(13C and 18O)
13C signatures of
respired CO2 to
investigate SOC
dynamics in
grassland under
elevated CO2
Pendall and King
2007

32. GHG Isotopic
technique
Experimental work References
CH4 13C natural
abundance
Enriched products
(13C–CH4 and
14NH4 15NO3,
15NH4 15NO3)
13C signatures from DOC isolates
found in water, peat, and
agricultural drains to examine
relationships with formation of
trihalomethane (THM)
To study the effects of elevated
CO2 concentrations on the
emissions of N2O and CH4
(oxidation/emission), 14NH4
15NO3 and 15NH4 15NO3 enable the
determination of respective
contributions of nitrification and
denitrification to N2O emissions
Bergamaschi et al.
1999
Baggs and Blum
2004

33. Moisture measurement
Probe contains radioactive
material ,that emits rapidly
moving neutrons.
Only slowed neutron are
counted. The more slowed
neutron that return .The greater
the water content of soil.

34. Gamma ray attenuation
technique
Ferraz and Mansall 1999
This technique was discovered by
Von Bavel et al. in 1957.
It performs a dual function of
measuring water content of soil and
bulk density
137 Cs and 241 Am used as a source
of gamma radiation.

35. Use of radioactive nucleotide
in erosion study
c
FRN with precipitation(p)
Erosion site
Deposition site original soil level
Resulting soil level
 137Cs used for long
term process
210Pb, 7Be for medium
and short term analysis
Methodology-
Comparison of FRN
activity at individual
site wit reference site
i.e. where no erosion
nor deposition occur
Felipe Zepata 2003 IAEA

36. Future area of research
Plant silicon signature to determine weathering status of
soil.
Understanding environmental behaviour and cycling of
toxic heavy metal in soil.
E and L value concept can be applied to study labile form
of various elements.
Various heavy metal isotopes used for finding hyper
accumulator plant for remediation of heavy metal in soil.

37. Contd…..
Isotope tracer technique opening the door for nanotechnology
implication .
Isotopes of various micronutrient can be used to understand
chelating chemistry.
Understanding characteristics and ameliorating effect of
Biochar application by IRMS of 13 C and compound specific
isotope of nitrogen.

38. UNLOCK THE
SECRETS OF SOIL
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