Increasing urbanization and industrialization have resulted in a dramatic increase in the volume of wastewater generated worldwide. Consequently, sludge production is steadily increasing and its transformation into biosolids can create alternative sources of nutrients and alleviate environmental problems. Biosolids are defined as an organic product, derived from a wastewater treatment process, which can be beneficially used as a soil fertilizer or conditioner. Biosolids are valuable sources of organic matter, N, P, and some micronutrients that improve soil characteristics and have beneficial effects on plant growth and biomass production. Feeding organic matter, primarily containing N and P, back into the natural cycle forms the basis of using sewage sludge and other organic wastes on soils. However, the benefits from biosolids application have to be weighed against potential deleterious effects such as an increased rate of nitrate leaching, contamination of soils and crops with human pathogens and metals, causing nutritional disorders in crops, an increase in soil salinity, contamination of groundwater with pesticides, hormones, and pharmaceuticals, and decreased stability of native soil organic matter.

This special issue intends to gather the most recent scientific information on the subject around the world. The special issue must provide a reasonable assessment of what is new, what is current, what needs to be known, or what should be done on the interdisciplinary topic of soil application of biosolids. Authors are invited to submit manuscripts for consideration to be published in this special issue, covering the following topics (but the editors also welcome papers on other related topics):

• Agronomic application: rates, methods, and economics
• Mineralization of organically bound elements
• Soil availability of nutrients
• Plant nutrient uptake and nutrition
• Biosolids N and P management
• Fate of pollutants and interactions with native soil components
• Heavy metals, including robustness of current application guidelines
• Changes in soil organic matter fractions
• Hazardous organic components, including human pathogenicity
• Effect on soil organisms
• Effect on soil physical conditions
• Potential for carbon sequestration

Before submission authors should carefully read over the journal's Author Guidelines, which are located at http://www.hindawi.com/journals/aess/guidelines/. Prospective authors should submit an electronic copy of their complete manuscript through the journal Manuscript Tracking System at http://mts.hindawi.com/ according to the following timetable: