An assessment of cropland application of alum sludge

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Virginia Tech

Previous research has shown that crop land application of alum sludge can be a valuable method of residuals disposal and has been demonstrated to cause no adverse effects on soil properties and crop yields. Studies have shown that with good soil management practices essential plant macronutrient levels can be maintained to support good crop growth.

This study investigated the application of water treatment residuals in both field studies and greenhouse pot studies in order to determine the effects on soils properties and crop yields. Alum sludge collected from the Blacksburg-Christiansburg-VPI Water Authority and Radford Water Treatment Plant was land applied in the Spring of 1992. Two separate crop rotations, corn followed by wheat, were grown and harvested during the two-year field study. A greenhouse pot study using lettuce and radish plants was initiated in the Spring of 1993.

Soil and plant tissue samples were collected and analyzed for the field and greenhouse studies. Harvest yields were also carefully monitored and recorded. The results of the laboratory analysis provided information on nutrient concentrations in soil and uptake by plants, and also soil and plant tissue elemental accumulations. Alum and PACI sludge at loading rates of up to 2.5% had no negative impacts on wheat yield. The growth study using lettuce and radish plants concluded that residual additions at low levels improved crop yield and that residual aging prior to land application was essential for good yield.