اثرات تجمعي و باقي مانده لجن فاضلاب بر پايداري خاكدانه ها نفوذپذيري و جرم مخصوص ظاهري خاك

The Effect of Cumulative and Residual Sewage Sludge on Aggregate Stability, Bulk Density, and Infiltration Rate

Sewage sludge is rich in organic matter that can improve soil fertility as well as soil physical properties. The objective of this study was to determine residual and cumulative sludge application on soil physical properties. Four rates (0, 25, 50, and 100 t ha-1) of sewage sludge were applied to a clay loam soil (fine Loamy, Mixed, Thermic, Halargid). To determine cumulative and residual effect on soil physical properties, in the second year, each plot (15x3) m) was divided into two sub-plots (3x3 and 3x9 m) and sewage sludge was added to the larger portion at the same rates as before. Bulk density, infiltration rate, aggregate stability, and organic matter content were measured 100 and 210 days after the sludge applications. Application of sewage sludge in the second year significantly increased infiltration, hydraulic conductivity and decreased bulk density. Residual sludge had similar effects, but as the time passed and organic matter decomposed, the soil physical properties approached the values in the control plots. The results indicate that the effect and duration of sludge application depended on the sludge rate and time of sludge application.