جستجوی مقالات مرتبط با کلیدواژه « Corey » در نشریات گروه « آب و خاک »

One of the ways to express physical behavior of soil is to describe the soil structure. Since physical soil could not be measured directly, therefore, the special properties defined as indicators, are used to express the soil physical quality. of different indicators, S-index is used to express the physical quality of the soil which is the slope of the soil water retention curve at inflection point. It seems that little research has been done on the effect of landuse on the S-index, then The purpose of this study was to compare the results of S-index of three different soil water retention curve models of the moisture characteristic of the soil (Van Genuchten, Brooks-Corey and Grant-Groenevelt Models) in 5 different land uses in Jiroft city. For this reason, 350 disturbed and 350 undisturbed soil samples of different landuse (citrus, palm, arable, forest and combinatory) were analyzed. Some of the physical and chemical features of the soil, including sand, silt, and clay percentage, the electronic conductivity at saturation, Bulk Density, the percentage of the total porosity and the percentage of the Organic Matter were measured. Also, the amount of the soil moisture in suctions 0, 10, 30, 50, 100, 300, 500, 1000 and 1500 KPa was determined using pressure plates. The results showed in the study region the best physical quality of the soil was seen in palm land use. All landuses, except forest, had high physical quality. High value of S index in citrus, palm, and arable land uses can indicate better soil management at the start of farming. In combinatory land use, due to Simultaneous cropping of alfalfa and palm, alfalfa causes more organic matter to be returned to the soil and as a result, the soil structure improves. Which is displayed at high value of S index. In general, The S index was higher in landuses where the soil had better structure or management operations were improved. because of the distinction between the soils with closely physical quality, Van Genuchten model was better and more appropriate than the other two models in assessing the physical quality. In general, despite the slight differences in citrus, palm and cultivate landuses, palm landuse had a higher mean of S index. So that their values in Van Genuchten, Brooks-Corey and Grant-Groenevelt models were 0.06, 0.06 and 0.04 respectively. The results of this study showed that the Van Genuchten model accuracy was better in estimating and evaluating the soil quality due to the greater differentiation between the soils with close physical quality. Because the fitting of Soil water characteristic curve had a higher R2 (R2=0.92). However, due to low differences with two other models, in particular the Brooks and Corey model (R2 =0.87), It seems that, in different landuses, a suitable model for assessing soil quality varies. Therefore, it is imperative that this index and other indicators of soil physical quality assessment in different climates are further examined.

The van Genuchten (vG) function is often used to describe the soil water retention curve (SWRC) of unsaturated soils. The objective of this study was to evaluate a method to determine the vG model parameters m and α of 100 soil samples of Guilan province from the fractal dimension of SWRC. Also, we used two models introduced by Lenhard et al and vG for estimating m from pore size distribution index of Brooks and Corey (BC) model. In both of the mentioned methods, the relationship between pore size distribution index of BC and SWRC fractal dimension was used. Also, vG parameters using Rosetta software were estimated and then, the amounts of vG parameters from the Rosetta, fractal method and RETC were compared. Results showed that Rosetta software had a better estimation of vG parameters than the Rosetta. The estimated vG model parameters m and α obtained with the above-mentioned different methods, in conjunction with measured saturated water contents, were used to estimate water contents at different matric potentials and compared with determined values by RETC via fitting of vG model on the measured values. The estimated SWRC data via fractal method were compared with those obtained with the Rosetta model. Results showed that fractal method had more accurate performance for prediction of SWRC than the Rosetta. Even though, the Rosetta software could lead to better estimates of the vG model parameters than the fractal approach, it was not capable of predicting SWRC as accurately as the fractal approach. This is due to the fact that estimation of the water content is a result of an interaction between the estimated vG model parameters, α and m.