The effect of measurement methods on saturated hydraulic conductivity in eastern loess lands of Golestan province

Saturated hydraulic conductivity (Ks) is one of the most important properties of soil that is essential for soil and water studies. It is a key input parameter to most watershed hydrology and soil erosion simulation models. Therefore this research aimed at comparison of different measurement methods of saturated hydraulic conductivity in different landuse types including forestland, rangeland, Agriculture (with vegetation) and Agriculture (bare & plowed) in the eastern loess lands of the Golestan province.
To measure the saturated hydraulic conductivity both field and laboratory methods were used. Considering the availability of equipments, two field methods including double rings and tension Guelph permeameter disk and one laboratory method of the constant-head conductivity test on undisturbed soil core were employed. Infiltration tests were conducted at 12 locations (in four landuse types with 3 repetitions). Furthermore, in order to determine some of soil physical properties in each location, one disturbed and one undisturbed soil sample were taken. For statistical analysis of results the completely randomize factorial design with two treatment factors was used within SAS 9.0 software.
The results of both comparisons between the influence of the measurement method and the type of landuse on the saturated hydraulic conductivity, showed that the landuse influence on hydraulic conductivity at the confidence level of 95% was not significant but the influence of measurement method with the same confidence level was significant so that a significant difference between the laboratory method and two field methods was observed. Among two measuring categories, the laboratory method due to smaller sample sizes had the highest coefficient of variation while the field method of tension Guelph permeameter disk had the least coefficient of variation due to restriction of flux to micropores and preventation from water flow through cracks and macropores.
According to the results obtained in this research, without considering the landuse effect is generelized to all placed landuses in these regions. While that the measured saturated hydraulic conductivity by laboratory and field methods could not to be apply and generalized instead of each other. So given that the application objective of results and available equipment in every area should select the fitting method for measuring of the saturated hydraulic conductivity in this area.