AICRP on Management of Salt-affected Soils and Use of Saline Water in Agriculture, Agricultural Research Station, Gangavati, 583227, Karnataka. hebbar62@rediffmail.com
A large number of groundwater samples (1985 numbers) were characterized for fluoride (F–) content and related with the chemical composition [pH, electrical conductivity, Ca2+, Mg2+, Na+, sodium adsorption ratio (SAR) and residual sodium carbonate (RSC)] of groundwater in the semi-arid tracts of Northern Karnataka. The area receives an annual average rainfall of 500–600 mm and is predominated by both red and black soils. The results indicated that the average fluoride content increased with increasing pH (r=0.26**) while remained independent of soluble salt content. The cations viz. Ca2+ and Mg2+ showed inverse relationship with fluoride. Calcium was more significantly related to fluoride (r= - 0.20**) than Mg2+ (r= - 0.13*). The fluoride content remained largely unaffected by the Na+ content. The fluoride content in groundwater increased with increasing SAR (r=0.27**) and RSC (r=0.29**) probably due to increased solubility. Groundwaters with higher pH, SAR and RSC values (i.e., mostly alkali waters) are likely to have a higher F– content in irrigation water while a higher Ca in groundwater may decrease the F– content.
Fluoride, groundwater, pH, EC, Ca2+, Mg2+, Na+, SAR, RSC
