A sensitive indicator to Management Practices

1. Permanganate oxidizable carbon(POXC) : A
sensitive indicator to Soil quality parameters
DEPARTMENT OF AGRICULTURAL CHEMISTRY AND SOIL SCIENCE
FACULTY OF AGRICULTURE
BIDHAN CHANDRA KRISHI VISWAVIDYALAYA
Speaker: Dibakar Roy
M.Sc. (Ag.), 3rd Semester
Chairman: Professor Biswapati Mandal
Course No. ACSS-591 SEMINAR-1 Date:21.03.2016

2. • Global storage of soil organic carbon is estimated o be- 1502 pg c in
the first 1 meter of soil (jobbagy and jackson, 2000).
• Labile constituent decomposes within few weeks or months.
• Stable form can persist in soil for years or more than a decade.
• Labile soil organic pool is relatively small fraction of TOC that responds
quickly to changes in soil management (weil and Magdoff,2004).
SOC
Labile Form
Stable Form
Introduction
Form

3. The labile fraction is important in terms of soil quality.. Because
Soil aggregate formation (Tisdel and oades, 1982)
Mineralization of Soil C and N (Gunapala and scow,1998)
Mineralization of S ( Banerjee and Chapman,1976
Mineralization of P (Jenkinson and Ladd, 1981)
Related wih Microbial biomass carbon ( Sparling, 1982)
Related with Particulate organic matter ( Culman et al, 2012)

4. Permanganate oxidizable carbon (POXC) is a simple method
for estimating- Labile organic carbon.
It involves- Oxidizing soil sample with known concentration
of KMnO4 and then measure changes in concentration by
Spectrophometry.
Most frequently the C- fraction determined by- KMnO4 is
termed- Active Carbon ( Weil et al, 2003).
What is permanganate oxidizable carbon?

5. • First, Loginow et al.(1987) used 0.033M, 0.167M, 0.333M potassium
permanganate to fractionate soil organic carbon based on susceptibility to
oxidation .
• Four fractions have been identified., Cꟾ , Cꟾꟾ, Cꟾꟾꟾ & CꟾV .
Loginow et al.(1987)

6.  Blair et al. (1995) estimates degree of lability of Soil carbon by treating soil
sample with 0.333 M potassium permanganate (KMnO4) and to oxidize a
portion of the carbon and determine the total carbon by combustion, two
fractions of C can be measured.
 These fractions represent carbon of different lability,
 Fraction 1- Labile Carbon ( Cl), which is oxidized by- 0.333 M KMnO4 and
 Fraction -2 Non-labile carbon, (C nl) which is not oxidized by 0.333 M
KMnO4 .

7. • Blair et al. (1995) used a reference site to compare changes of soil carbon
under different cropping and management practices and developed new
parameters – Carbon pool index (CPI), Labiity index(LI) , Carbon management
Index (CMI).
• The loss of Labile C is of greater importance than loss of Non labile C. To
account for this lability index is developed..
• Carbon management Index (CMI) can then be calculated as-
•
• Concluded that there was no Ideal value of CMI. This index provides a
sensitive measures of the rate of change in soil C dynamics of systems
relative to a more stable reference soil.

8. Errors in Blair's Method
• Conc. KMnO4 used is sufficiently high enough. This concentration 0.333M
is close to the solubility limit of KMnO4 0.4M.
• When concentration of KMnO4 more than 0.025 M results greater
standard errors in measurement and reduced ability of ANOVA to
distinguish between two management practices.
• High conc. of KMnO4 reacts a large fractions of TOC (14-27%), which is
much more than labile fraction.
• Low sensitivity to C cycling and other soil properties.
Wail et al. (2003)

9. • Wail et al.(2003) modified the method followed by Blair et al.(1995)
• Wail et al.(2003) found that 0.333 M Potassium permanganate react with large
fractions of TOC which is much more than Labile fractions. He used a series of
conc. ranging from 0.01M to 0.1M KMnO4, and found that 0.02M KMnO4
produces consistent and management sensitive results.
Modifications done by Wail et al. (2003)
Parameters Blair et al. (1995) Wail et al. (2003)
Conc. of KMnO4 used 0.333 M 0.02 M
Shaking time 15 Min 2 Min
Methods 15 min shaking followed
by Centrifugation for 5
mins
2 min shaking followed
by standing for 10 mins
settling
Supernatant Clarification Centrifugation at 3000
rpm for 5 min followed
by shaking.
Here 0.1 M CaCl2 used
along with KMnO4 for
Settling.
Wavelength chosen 665 nm 550 nm

10. • Wail et al.(2003) determined the portion of SOC oxidized by 0.02M KMnO4
termed as- Active carbon.
• Determined relation between active carbon with other soil properties
 Substrate –induced carbon,
 Basal respiration,
 Microbial biomass carbon,
 Soluble carbohydrates,
 Total organic carbon
 K2SO4 oxidizable carbon.
• Developed field kit for testing Soil quality in field condition. Validate the test
result with lab data.

11. Comparison between Methods of Blair et al. (1995)
and Wail et al. (2003)
Parameters 0.333 M KMnO4 Carbon
by Blair et al. (1995)
0.02 M KMnO4 Carbon
by Wail et al. (2003)
Substrate induced
respiration
R2 – 0.60 ** R2 -0.74 ***
Basal respiration R2 – 0.46 R2 – 0.56 *
Microbial biomass R2 -0.79*** R2 -0.85***
Soluble carbohydrates R2 -0.68** R2 -0.84***
Total organic carbon (TOC) R2 – 0.77*** R2 – 0.69**
K2SO4 Extractable carbon R2 – 0.51* R2 – 0.51*
Wail et al. (2003)

12. Relationships with Soil properties and POXC

13. Relationship with Soil texture
• POXC (0.033 M KMnO4 ) is less correlated with Clay/OC content.
• POXC (0.033 M KMnO4 ) highly correlated with Silt/OC and (Clay + Silt)/OC
content.
Padre and Ladha (2004)

14. Relationship with TOC and Walkley-Black Carbon (OC)
 Padre and Ladha (2004) found a higher linear correlation
between 0.033M KMnO4 oxidized carbon and Total organic
carbon (TOC) and Walkley- Black carbon than obtained by Wail
et al. (2003) and Blair et al. (1995)
• Linear correlation with TOC
• Linear correlation with OC

15. Relationship with Microbial Biomass Carbon (MBC)
• Culman et al. (2012) analyzed soils
from 53 different sites with 0.02M
KMnO4 and determine correlation
with MBC.
• They obtained varying R2 between
Active Carbon and MBC ranging from-
0.19 to 0.85.
• Padre & Ladha (2004) determined
linear correlation with MBC and
Permanganate oxidizable carbon
(0.033M).
• They concluded non significant
correlation between Active Carbon
and MBC, R2 – 0.20
Culman et al. (2004) Padre &Ladha (2005)

16. Relationship with Particulate organic Carbon (POC)
• Permanganate oxidizable
carbon was more closely
related with Smaller-sized
(53-250µm) POC than larger-
sized (250-2000µm) POC .
• More closely related to
heavier (>1.7 g/cc) POC
fractions than lighter POC
fractions.
• R2 between POXC and POC of
different size , 1000-2000µm ,
250-1000µm, 53-250µm are
0.04, 0.31 and 0.63
respectively.
Culman et al. (2012)

17. Culman et al.(2012)

18. Relationship with Nitrogen And Humic Acid
• Tatzber et al.(2015) analyze the POXC from three long term experiments in
Austria.
• Significant positive correlation obtained with - TOC, Total Nitrogen, Humic acid
content and Remaining C14 labelled material.

19. Relationship HA, FA , HA + FA content, and Polysaccharide
content and Labile carbon of organic materials
Blair et al, ( 1995)

20. Relationship with Soluble Carbohydrate and Lignin content of organic material
• Permanganate oxidizable Carbon
(POXC) was significantly
correlated with Water soluble
Carbon(WSC).
• POXC of the organic materials
significantly correlated with
Lignin content, but not with TOC
content and lignin/N content.
Padre and Ladha (2004)

21. Permanganate oxidizable carbon of some organic material
Organic
materials
Total C
( g/kg)
Total
N
(g/kg)
C/N Lignin
(g/kg)
Lignin/N
(g/g)
POXC
(1 hour)
g/kg
POXC/T
OC
(1 hour)
%
POXC
(6 hour)
g/kg
POXC/T
OC
(6 hour)
%
FYM 325 19.3 19.6 110 5.2 45.4±
1.0
15.4±1.8 76.2±1.7 25.7±0.9
Rice Straw 373 8.0 54.6 93 11.6 35.5±0.6 8.9±0.5 66.2±0.2 16.5±1.2
Wheat Straw 458 4.4 121.
0
140 31.7 47.4±1.8 10.5±1.1 88±1.1 19.5±0.0
Azolla 444 41.5 12.5 185 4.5 64.7±0.9 14.5±0.2 99.4±0.3 22.3±0.2
Dhaincha 452 19.9 26.5 55 2.8 31.1±1.8 6.9±0.4 65.6±0.7 14.5±0.2
Padre and Ladha (2004)

22. Relationship with Crop management and tillage practices

23. Cropping or
Grazing history
(years)
Labile
Carbon
( C L)
mg/g
Non- Labile
Carbon
(CNL)
mg/g
Total Carbon
(TOC)
Carbon pool
index (CPI)
Lability of
Carbon (L)
Lability Index
(LI)
Carbon
management
index (CMI)
Nyngan (Solonized brown Earth, Palexeralf) – Continuous cropping
Uncropped 4.50 13.53 18.03 -- 0.332 -- --
4 yrs cropping 2.21 10.38 12.59 0.70 0.213 0.64 45
Gunnedah (Black Earth, Pellusert)- Continuous cropping
Stock route
Grazing
3.62 16.83 20.45 -- 0.256 -- --
7 yrs cropping 1.55 9.18 10.73 0.51 0.169 0.66 33
Warialda (Red Earth, Paleustalf)- Continuous cropping
Lightly grazed 3.99 12.78 16.77 - 0.312 -- --
18 yrs cropping 1.02 6.49 7.51 0.45 0.157 0.50 23
16 yrs cropping
and 2 yrs
lucerne
1.62 7.50 9.13 0.54 0.215 0.69 38
Labile and Non- Labile C and Carbon Management index for some cropped and
uncropped soils in New south Wales, Australia
Blair et al. (1995)

24. Cropping
history
(years)
Labile
Carbon
( C L)
Non- Labile
Carbon
(CNL)
Total Carbon
(TOC)
Carbon pool
index (CPI)
Lability of
Carbon (L)
Lability Index
(LI)
Carbon
Management
index (CMI)
Marian ( Yellow Podzolic. Haplustalf) – Trash Buring
0 4.08 10.91 14.99 -- 0.374 -- --
90 1.54 7.04 8.55 0.57 0.219 0.59 34
Victoria planes (Black Earth, Pelloxerept)- Trash Mulching
0 3.56 15.22 18.78 0.234 -- --
15 4.00 19.69 23.69 1.26 0.203 0.87 110
Labile and Non- Labile C and Carbon Management index from sugarcane cropped
and adjacent non-cropped areas of Mackey, Queensland
Blair et al. (1995)

25. Contents of active carbon(AC), total organic carbon(TOC), AC/TOC
ratios and total nitrogen content (Nt) from different cropping systems
of the C-14 labelled cropping field in Austria
Cropping
System
AC (mg/kg) AC/TOC (%) TOC (g/kg Soil) Total N (g/kg)
Crop Rotation 325±11 1.87±0.09 17.2±1.3 1.38±0.06
Monoculture 297±13 1.78±0.12 16.8±1.3 1.26±0.04
Permanent
Bare Fallow 171±11 1.32±0.08 12.6±0.5 0.92±0.02
Tatzber et al. (2015)

26. Different tillage practices and POXC
 Variation in POXC content was found in top soil layer of different tillage
systems.
 With in 0-10 cm, POXC is greater in Minimum tillage and Reduced tillage
compared to Conventional tillage.
 With in, 10-20 cm, POXC is lower in Reduced tillage, no significant
difference in Conventional tillage and Reduced tillage.
 With in, 20-30 cm, POXC content was higher in Conventional tillage
compared to Minimum Tillage and Reduced tillage.
Tatzber et al. (2015)

27. Tatzber et al. (2015)
POXC is highest in Minimum
tillage system, and Lowest
in Conventional tillage
system
POXC is highest in
conventional tillage
system

28. Conclusion
Permanganate oxidizable carbon is not protected by soil aggregates. High clay
content does not effect POXC value.
Highly correlated with soil properties like MBC, Particulate organic matter,
total organic carbon , total nitrogen, Soluble carbohydrate and lignin content.
Reflects variation in crop management practices. Continuous cultivation
reduces Labile carbon, where as addition of leguminous crop in rotation
increases Labile carbon. Residue management increases Labile carbon.
Crop rotation is beneficial over Mono cropping in terms POXC content.
Minimum tillage practices has higher POXC content than Conventional tillage .