Amelioration of an arid-land sodic soil with aluminum polynuclear species and humic acid.

摘要

The conventional methods used for sodic soil reclamation are often difficult and time consuming. This research was conducted to examine the effects of aluminum polynuclear species, humic acid, gypsum and aluminum polynuclear species plus humic acid treatments on the hydraulic conductivity (sc K), exchangeable sodium percentage, and cation exchange capacity (CEC) of a sodic soil. Aluminum was added at OH/Al molar ratios of 2.0 and 2.5 to Pachappa soil (fine-loamy, mixed, thermic Mollic Haploxeralf) and at 2.5 to Arlington soil (mixed, thermic, Haplic Durixeralf). Irrigation water with 0.01 M Cl{dollar}sp-{dollar} and SAR 20 and tap water with SAR = 1.33 were used to leach the Pachappa and Arlington soils, respectively.; The adsorption of aluminum was linear and irreversible at pH 5.0 and 7.0. The sc K and infiltration rate increased significantly (p {dollar}<{dollar} 0.05) with the amount of aluminum added. There was no significant difference between the two OH/Al molar ratios tested. The aluminum treatment did not significantly (p {dollar}<{dollar} 0.05) change the CEC and pH of the soils. Nonexchangeable aluminum was found to have a dominant role in stabilizing soil aggregates. The treatment effects on sc K of Arlington soil were in the following order: aluminum OH/Al = 2.5 {dollar}approx{dollar} humic acid pH 3.5 {dollar}>{dollar} humic acid pH 3.5 plus aluminum OH/Al = 2.5 {dollar}>{dollar} gypsum {dollar}>{dollar} humic acid pH 3.5 raised to pH 7.0 {dollar}approx{dollar} humic acid plus aluminum OH/Al = 2.5 {dollar}>{dollar} control {dollar}>{dollar} humic acid. The reduction in the ESP is ranked in the following order: humic acid pH 3.5 plus aluminum OH/Al = 2.5 {dollar}>{dollar} gypsum {dollar}>{dollar} humic acid pH 3.5 {dollar}>{dollar} aluminum OH/Al = 2.5. The other treatments did not appreciably lower the ESP. Humic acid pH 3.5 treatment was not considered further, as pH 3.5 is too low for agricultural production. Also the adsorption of humic acid was reversible in the pH range of arid-land soils. Based on the quantity of water and the time required to achieve an ESP of {dollar}<{dollar}20, the effectiveness of treatments may be ranked as humic acid pH 3.5 plus aluminum OH/Al = 2.5 {dollar}<{dollar} aluminum OH/Al = 2.5 {dollar}<{dollar} gypsum.