Multiple applications of paper mill sludge in an agricultural system: Soileffects

Little information exists regarding the effects of field-scale application of paper mill sludge on soil properties. A 5-yr field study determined the long-term effects of land application of paper mill sludge on an agricultur al soil. The goal of this study was to determine the responses of soil chem ical and physical properties to multiple applications of sludge. Five rates of sludge application were tested, ranging from 0 to 225 Mg ha(-1) in mult iple applications under three management protocols: applied once, applied i n alternate gears, or applied annually. Results indicate strong relationshi ps between added sludge C and several soil physical properties. Increases o r maintenance of soil C were observed when sludge was applied annually or b iennially, but little residual effect of the single application was seen af ter 5 yr. Significant increases were observed in soil aggregation and moist ure holding properties at higher rates of sludge application and when cumul ative C additions reached 225 Mg ha(-1) in other sludge application rates. It was concluded that long-term paper mill sludge application can be manage d to effect positive changes in soil physical properties that are correlate d to soil quality.