Development of salt-affected lands in Southern Sri Lanka with special reference to Hambantota district

Abstract

A detailed soil survey was conducted throughout the Hambantota district to determine the soil pH and Electrical Conductivity (EC) o f the soils. The data points were taken by using GPS. The soil salinity map was drawn by using GIS and Remote Sensing technique. Results revealed that no strongly saline areas were found where soil EC was more than 16ds/m while 24.8sq.km or 1.2% o f strongly saline areas where soil EC was from 8-16ds/m, 433.5 sq.km or 20.5% o f moderately saline areas where soil EC wasfrom 4-8ds/m, 806 sq.km or 38% o f slightly saline areas where soil EC was from 2-4 ds/m and 855.2sq.km or 40.4% o f non-saline areas where soil EC was from 0-2ds/m were found in the district. A series o f pot experiments were also conducted to screen the salt-tolerant tree species (i.e (Katuandara (Acacia leucoploea), Kottam ba (Terminalia catappa), Ip il-Ip il (Leucenea leucocephala), Castor (Ricinus communis), Ranawara (Acasia auriculata L), Wood Apple (Feronia limonia), Tamarind (Tamarindus indica), Kathurumurunga (Sesbania grandiflora) and Cashew (Anacardium occidentale L)) available in the district. Plant height, Number o f leaves, dry weight o f above ground biomass, root depth and root biomass) were taken once a month up to 4 months o f transplanting in polythene bags. According to the results, the tree species used fo r the experiments could be ranked in order o f tolerance to salinity levels as follows. Katuandara > Tamarind > Wood Apple > Kottamba >Ipil-Ipil > Ranawara > Kathurumurunga > Castor > Cashew. These selected tree species (i.e. Katuandara, Tamarind, Wood Apple, Kottamba and Kathurumurunga were established in the salt affected areas in Hambantota district and growth performances and soil salinity were monitored up to one year. Results revealed that even though site was strongly saline (salinity was 9.5ds/m), several tree species (Katuandara, Kottamba, Kathurumurunga etc.) were able to grow successfully and soil salinity was reduced in top and second 10cm soil layers form 1.6-2ds/m and 1.0-1.2ds/m respectively.