Soil dynamics following long-term application of poultry manure and sewage sludge on grassland

Organic manures can complement or even replace mineral fertilization of a pasture within a sustainable production system. In this article, an evaluation is made of the changes occurring in some properties related to soil quality after 7 years of applying two types of organic manures, poultry manure (PM) and sewage-sludge pellets (SP), compared those produced by normal mineral fertilization and a control. Both organic manures were effective for improving the quality of the soil surface horizon; however, PM appeared more effective in accumulating organic matter and improved more soil properties than did SP. The PM in particular improved soil aggregation, microbial development, and carbon (C) and nitrogen (N) storage in the form of organic matter. On the other hand, SP lowered soil pH and increased β-glucosidase activity. The soil water-storage capacity and conservation also increased with the application of both organic manures.