Permangante oxidizable carbon (POXC) in Soil

Permanganate oxidizable carbon(POXC) : A sensitive indicator to Soil quality parameters

DEPARTMENT OF AGRICULTURAL CHEMISTRY AND SOIL SCIENCEFACULTY OF AGRICULTURE

BIDHAN CHANDRA KRISHI VISWAVIDYALAYA

Speaker: Dibakar RoyM.Sc. (Ag.), 3rd Semester

Chairman: Professor Biswapati Mandal

Course No. ACSS-591 SEMINAR-1 Date:21.03.2016

• 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

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)

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?

• 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, C ꟾꟾꟾ & C V ꟾ .

Loginow et al.(1987)

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 .

• 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.

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)

• 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

• 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.

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)

Relationships with Soil properties and POXC

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)

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

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)

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)

Culman et al.(2012)

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.

Relationship HA, FA , HA + FA content, and Polysaccharide content and Labile carbon of organic materials

Blair et al, ( 1995)

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)

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/TOC

(1 hour) %

POXC(6 hour)

g/kg

POXC/TOC

(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)

Relationship with Crop management and tillage practices

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 croppingUncropped 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 croppingStock 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 croppingLightly 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)

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)

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)

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)

Tatzber et al. (2015)

POXC is highest in Minimum tillage system, and Lowest

in Conventional tillage system

POXC is highest in conventional tillage

system

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 .