shahab ansari

In addition to soil water content, soil matric potential is also important for plant growth. Soil water characteristic curve (SWCC) or soil moisture characteristic curve describes soil water content and soil matric potential relationship. Many models have been developed to describe the SWCCs and their fitting to the experimental data. However, their fitting accuracies in different soil textures, have been rarely investigated. In this study, matric potential-moisture data of 16 soil sample of forest station in Finland use to fit SWCC models. Nine well known and frequently applied SWCC models were fitted to the measured data. The most accurate models of total soil samples, each textural group and each textural class were estimated using root mean square error (RMSE), coefficient of determination (R2) and mean error (ME). Result showed that van Genuchten-Mualem, van Genuchten, Gardner and Brutsaert models had most accurate and Brooks and Corey model had least accurate to predict SWCC.

In recent years, researchers have considered new methods such as dry drainage, to control the soil water and salinity of the irrigated area of the fields in the arid and semi-arid regions because traditional drainage methods are expensive and need more water. Investigation of water and salts transport in these systems is essential for studying their function. In this study, effect of dry drainage on the soil water content, salinity, nitrate and chloride ion concentrations in a loamy soil was investigated using a physical model under the barley cultivation. Based on the results, dry drainage led to transport a significant part of the salts entering in the irrigated area to the non-irrigated area that accumulated on its soil surface, in addition to controlling soil moisture in the irrigated area. Based on the results, at the end of the experiment, maximum increase of salinity, nitrate and chloride concentrations on the soil surface of the irrigated area were 145, 384 and 135%, respectively, and for the soil surface of the non- irrigated area were 270, 1070 and 160 %, more than of initial values at the start of the experiment. Therefore, dry drainage system was able to control the soil salinity of the irrigated area by transporting the salutes to the non-irrigated area for proper barley growth

In recent years, decreasing water resources stimulated researchers to consider dry drainage in dry area due to less cost and water requirement. Understanding mechanism and the amount of different salts transportation from the irrigated area to the non-irrigated area is necessary to evaluate the performance of this system and the pre-implementation of purification and recovery projects of the salt collected from the non-planted surface area. In this study, the effect of dry drainage on the transportation of important cations and salinity changes (EC) in a loamy soil were investigated using a physical model under barley cultivation in 2017. The physical model was made of galvanize and had useful length, width and height of 2, 0.5 and 1 meter respectively. On the basis of the results, changes in sodium and calcium concentration profiles were similar and they were different from changes in potassium and magnesium concentration profiles. Sodium, potassium and calcium ions were accumulated in the upper soil layer, but magnesium was accumulated in the lower soil layer of the non-planted area. At the end of experiment, sodium, calcium, potassium, magnesium concentrations and SAR at the soil surface of non-irrigated area were 210, 410, 125, 115 and 126 percent of their initial values respectively. At the end of experiment, the soil surface salinity of the planted and non-planted areas was increased up to 145 and 270% of their initial values, respectively.