Effect of biosolids on the organic matter content and phosphorus chemical fractionation of heated volcanic Chilean soils

Abstract

Biosolids produced in wastewater treatment plants with high organic matter (OM) content can be used to reclaim organic components in heated soils. The impact of biosolids amendment on soil pH, electric conductivity (EC), exchangeable cations, OM content, and phosphorus (P) chemical fractionation in 3 heated volcanic soils in southern Chile was investigated in a 4-month incubation study. In amended heated soils, pH, EC, OM content, and exchangeable cations were greater than in control soils. The control OM content was increased by biosolids, and the incubation time effect to reclaim the organic component was important in Andisols and Inceptisols. The pH decreased with incubation time, reflecting the buffer capacity of volcanic soils, and EC increased. In the heated incubated soils, inorganic P was in general higher than organic P. Phosphorus distribution showed little difference with incubation time, showing that after a short time (4 months) biosolids P was not significantly redistributed to organic P; however, more available P forms (Olsen P) were determined. It can be concluded that biosolids are a valid option for reclaiming the OM content lost in soils affected by forest fires. However, an important amount of inorganic P, strongly fixed in volcanic soils, with a relative contribution of available forms for plants, could potentially contribute to soil and water pollution.