SPATIAL VARIATION OF FLUORINE IN AN INDO-GANGETIC ALLUVIAL PLAIN OF INDIA

Spatial variability of water-soluble fluorine (F) in Haryana soils was studied geostatistically. Semivariogram based on 470 samples at a nod e of 10 x 10 km grid showed F to be correlated over space for a separa ting distance of 225 km between two observations. Fluorine was estimat ed by point and block kriging methods at unsampled sites (5 x 5 km gri d). The means obtained by these three methods were almost the same, th ough the estimation variances calculated by point and block kriging we re 1.19 and 8.76 times less than those obtained by the classical theor y. However, block kriging variance was 7.34 times less than the point kriging variance, a good gain in efficiency. An isarithmic map of F dr awn from the paint kriged estimates was very spotty and discontinuous, whereas in the map prepared by block kriged estimates the spottiness disappeared to a greater extent, resulting in a better continuity. The estimated number of samples were 125 (classical), 104 (point kriging) at 99 per cent confidence level. However, the number of samples requi red at this precision were only 14 by block kriging, a good gain in pr ecision.