Management of irrigation and drainage systems for salt balance: A solute transport study for saline and waterlogged soils.

摘要

A study was conducted to evaluate the effects of sodium chloride (NaCl) and calcium chloride (CaCl{dollar}sb2{dollar}) at different concentrations in the soil profile on saturated hydraulic conductivity, salt movement, and transport of nitrate-nitrogen (NO{dollar}sb3{dollar}-N) and atrazine to the groundwater. Also, the effects of various water table depths were evaluated on salt movement and the fate of NO{dollar}sb3{dollar}-N under simultaneous irrigation and drainage practices.; Two sets of experiments were conducted in the laboratory under simulated saline and waterlogged conditions. Three sets of soil columns (45, 75, and 115-cm long) were fabricated using PVC pipes of 20.0 cm diameter for this study. Large columns (115-cm long) were filled with a sandy loam soil brought from the bank of Squaw Creek river near Ames, Iowa. For one experiment, these long columns were filled with soil in seven layers of different bulk densities. For other four experiments, the soil was filled in the columns uniformly by mixing the entire soil profile to give a single bulk density for the entire column.; For the short columns, two types of soils were used (sandy loam soil from Squaw Creek and nicollet loam soil from Iowa State University Farm at Ankeny, Iowa) to pack the columns. These soils were packed in the columns at uniform densities of 1.40 and 1.25 g/cm{dollar}sp3{dollar} for sandy loam and nicollet loam soils, respectively.; The salt equilibria were obtained by mixing weighed amounts of salts in weighed amounts of soil, and by subsequent saturating the soil in the columns with desired salt concentrations. Four levels of salt concentrations (3200, 6400, 19,200, and 38,400 ppm) were used for different experiments.; The results of this study showed that hydraulic conductivity of the soil decreased with the increase in salt concentrations. But reverse effect of salt concentrations was observed when salt concentrations were increased six-fold. The NO{dollar}sb3{dollar}-N and atrazine leaching increased with increase in salt concentrations. The overall results of this study indicate that the simultaneous irrigation and drainage practices could be managed for soil reclamation by applying about 25 percent more water for irrigations. Also, nitrogen fertilizers can be managed better if proper irrigation and drainage systems can be designed for the benefits of the farmers by using some of the results of this study.