VARIABILITY AND SPATIAL DEPENDENCE OF PHYSICAL AND CHEMICAL PROPERTIES OF SOILS IN FCV TOBACCO FIELDS OF CTRI RESEARCH FARM AT JEELUGUMILLI OF ANDHRA PRADESH

Abstract

Studies on variability and spatial dependence of some physical and chemical soil properties in fluecured tobacco fields conducted at northern light soil farm, CTRI Research Station, Jeelugumilli during 1997-2000 revealed that standard deviation of soil pH was small in relation to the estimated mean. Values of standard deviation of organic C and soil-water retained at different matric suctions were medium while those of EC, Cl, available P and available K were very high in both soil layers. Normal distribution of soil properties over the entire farm was significant at 0.05 level with respect to soil pH in surface layer and available K in subsurface layer. Some soil properties followed normal distribution in some individual blocks. Values of EC did not follow normal distribution in any block. These results indicated high degree of variability of soil properties within blocks in both soil layers. The parameters were grouped according to the relative amounts of variability. In the lowest class was soil pH with a CV of about 10-11%. On the other hand were four parameters viz., EC, Cl, available P and available K, which were more variable, each with a CV greater than 42%. Variations for soilwater retained at different matric suctions and organic C were intermediate. Spectacular differences in CV values were not obtained between blocks for all soil properties studied except for a few differences in CV values of some properties. Very few numbers of samples are needed to estimate soil pH than the other parameters. Only 5 samples are required to estimate mean within 10% of true mean at 0.05 significance level. Soil-water retained at different matric suctions and organic C require about 31 to 52 samples whereas EC, Cl, available P and available K require 66 to 203 samples to estimate mean within 10% of true mean at 0.05 significance level. Autocorrelation function for different soil properties indicated spatial dependence of soil available P and available K up to 4 m and weak autocorrelation for Cl and organic C.