Effects of Polyacrylamide, Pumice and Municipal Compost on Some Physical and Chemical Characteristics of a Saline-Sodic Clay Soil

Salinity and sodicity are of major problems of arid and semi-arid regions soils and account for lowering soil quality. In order to improve the physical and chemical qualities of these soils, a composite sample of a saline-sodic clay soil (EC_e= 11.5 dS/m , SAR= 13.23) from Bilverdi agricultural research center of Islamic Azad University of Tabriz branch was collected. The experiment carried out in a greenhouse, was factorial with complete randomized design with 3 replications. The experimental factores (treatments) were a)polyacrylamide (PAM) (0, 0.25 and 0.5 g/kg soil), b) pumice (0, 50 and 100 ton/ha) and c) municipal waste compost (0, 30 and 60 ton/ha). After complete mixing of these amendments with pre-wieghed amount of soils in plastic pots, the pots were kept in the greenhouse under 18-25 ^◦c. The soil moisture varied in the range of 0.5 FC to FC. Ten wetting and drying cycles were imposed to the pots using tap water with EC=0.387 dS/m and SAR= 1.014. After incubating of the pots for 100 days under the described conditions pH, saturated electrical conductivity (EC_e), sodium adsorbtion rate (SAR) and organic carbon (OC) were determinded in the disturbed samples taken from the pots. Saturated hydraulic conductivity (K_s) and slope of soil moisture curve at the inflection point (S_i) were also determinded in undisturbed samples taken from the surface layers of the pots. Analysis of variance and mean comparisons between the treatments showed that pumice and compost reduced pHsignificantlyby 0.37 unit in comparision to the control. Pumice and PAM also reduced EC_e from 34.9  to 43.97 percent relative to the control. while compost raised EC_e by 186.69 percent relative to the control. The result clearly showed a positive effect of pumice and compost on reducing SAR by 58.97 percent and positive effect of PAM and compost on increasing OC by 26.67 percent in comparision to the control significantly. Due to strong adhesive effect of PAM for the soil particles, and thus its aggregation effect, this amendment  led to more larger pores and as a result significantly raised K_s up to 3 cm/hr (638.3%) and S_i to 0.074 unit (160.87%) as compared with the control. Generally, it seems that using PAM at the beginning of saline-sodic soils reclamation may considerably facilitate the practice because it greatly improves hydraulic conductivity. Taking the benefits of pumice or compost will be the next step