G L O B A L S Y M P O S I U MO N S O I L

P O L L U T I O N2 - 4 M A Y 2 0 1 8 | F A O - R O M E , I T A L Y

Recuperation of acid saline soil by application of organic amendments

Meththika Vithanage1, J.A.I. Senadheera2 , Viraj Gunarathna2

1Ecosphere Resilience Research Center, Faculty of Applied Sciences, University of Sri Jayewardenepura - Sri Lanka

2Environmental Chemodynamics Project, National Institute of Fundamental Studies - Sri Lanka

INTRODUCTION

Saline soils are formed during the accumulation of salts in the soil (Fig. 1). Saline soils are present all over the world (Fig. 2)

OBJECTIVES

To compare and evaluate the effects of organic amendments (biochar, composts and sewage sludge onto the soils) as individual applications on the reclamation potential of a saline-acidic soil has been thor-oughly studied in the Sri Lankan costal dry zone.

METHODOLOGY

Acid saline soil samples were collect-ed from the East coast of Sri Lanka, Kokkuvil, Batticaloa where samples were collected from first 20 cm. Air dried soil was sieved by 2 mm. Amendments were characterized and used as 16 incubation treat-ments with biochars manufactured at three different temperatures (300, 500, & 700 °C), compost from municipal solid waste and sludge from municipal sewage treatment, application as 1.0, 2.5, 5.0% w/w and control as respectively. Treated soils were subjected to laboratory incubation for 120 days at room temperature (26±1 °C).

MAIN RESULTS

Characteristics of Acid saline soils from Sri Lanka (Table 1)

CONCLUSION

• Based upon the findings of this study, compost might be consid-ered as a most suitable amend-ment for saline soils, since it great-ly reduced the salinity and acidity.

• Moreover, amending of soil by compost is enhancing the nutri-ent availability as well.

• In terms of biochars, best recla-mation is shown by 500 °C pro-duced BC than 300 and 700 °C, because low temperature pyro-lyzed biomass are efficient for inorganic contaminants due to the presence of more O-O- con-taining functional groups.

Fig. 1: Salt accumulation mechanims in the root zone of irrigated land Adopted from https://wle.cgiar.org/content/making-case-reusing-saline-water-and-restoring-salt-affected-agricultural-lands

Fig. 2: Global soil map affected by salinity. Adopted from Zheng (2014)

Restoration of salt affected soils

Physical Chemical Biological

Soil dredgingSoil washing

Application of chemical amendmentsGypsum

BioremediationUsing compost,

manure, and phytoremediation using halophytes

Fig. 3: Location of the sampling site

Electrical Conductivity (EC), pH, NO3-, PO4-3,

Cation Exchange Capacity (CEC), Exchangeable

Sodium Percentage (ESP), Total Organic Carbon

(TOC), Acid phosphatase (Acidpht), Alkaline

phosphatase (Alkpht) and Catalase activities (CA)

Parameter ValuesBulk  density   1.20  g/cm3

Water  holding  capacity 35.00  %Sulfate  (SO4

-­‐2) 567.5  mg/kgElectric  conductivity  (1:5) 8.15  dS/cm3

pH  saturated  (1:5) 3.82  Available  nitrate  (NO3

-­‐) 0.224  mg/kgAvailable  phosphate  (PO4

-­‐3) 5.440  mg/kgCation  exchange  capacity   32.68  cmol/kgSodium  adsorption  ratio   10.66Exchangeable  sodium  percentage  

67.62%

Total  organic  carbon   4.60%

Catalase  activity  6.86  ml  (0.05mol/l  

KMnO4)  /g/h

Phosphatase  activity  (acidic)158.24  µg  (p-­‐nitrophenol)/g/h

Phosphatase  activity  (alkali)60.95  µg  (p-­‐nitrophenol)/g/h

Postulated mechanisms of amendments interactions with inorganic contaminantsLeft: Postulated mechanisms of biochar. Circles on biochar particle show physical adsorption. I – ion exchange between target metal and exchangeable metal in biochar, II – electrostatic attraction of anionic metal, III – precipitation of target metal, and IV – electrostatic attraction of cationic metal. Right: Postulated mechanisms of compost interactions with organic contaminants

Biochar Compost

Sludge

Poster GSOP 2018 41-51.indd 152 19/04/18 19:49