Factors controlling the aggregate stability and bulk density in two different degraded soils amended with biosolids

Intensive agricultural practices generally lead to considerable reduction of organic carbon in soils. Moreover, the use of saline water affects physical parameters such as aggregate stability, and thus, bulk density. Organic amendments have been proposed as an effective method to improve physical properties of soils. In this paper, the effect of successive biosolids (sewage sludge) amendments on aggregate stability percentage and bulk density on two degraded soils (one salinized) have been evaluated during several samplings. Different relationships between these parameters (aggregate stability and bulk density) with organic carbon, carbohydrates and exchangeable sodium percentage have been observed in these soils. The application of biosolids increased significantly the organic carbon, carbohydrates and aggregate stability percentage, resulting in a decrease of the bulk density of both soils. In the non-salinized soil, the increase in aggregate stability was related to the increase in organic carbon and carbohydrates. But in the salinized soil, the increase in aggregate stability was related to the increase in carbohydrates and specially to the decrease in exchangeable sodium percentage. In both soils, the decreases in bulk density by the organic amendments were related to the increase in aggregate stability. Application of biosolids could be a successful practice to improve soil structure in degraded soils.