Drinking water treatment residuals as an amendment to alkaline soils: Effects on the growth of corn and phosphorus extractability

Drinking water treatment residuals (alum) are waste products of water purification that have potential for environmental remediation as a soil amendment and a potential plant growth medium. In this study, the influence of added Drinking water treatment residuals on the extractability and availability of phosphorus to plants; determination of the agronomic rate of alum to different agricultural soils and evaluation of the alum as ameliorating material for soil conditions and plant growth were investigated. In all studied soils, increasing drinking water treatment residuals rate up to 30 g/kg significantly increased dry matter yield. Application of 10, 20 and 30 g/kg alum significantly increased plant P concentrations in the plant materials (shoots and roots) taken from clay, sandy and calcareous soils. Further increase in alum application rate has resulted in negative significant impact on plants P concentration, especially in clay and calcareous soils, but in sandy soils the increase in phosphorusconcentration extended to 40 g/kg alum rate. Application of alum at rates up to 30 g/kg significantly increased available phosphorus concentrations of the three studied soils. However, application of alum at a rate of 40 g/kg to clay and calcareous soils significantly decreased available phosphorus concentrations. Combined analyses of all soils and alum rates studied clearly indicated significant relationship between available phosphorus concentration and phosphorus uptake (r = 0.87, P < 0.001). Based on our experiment results, the rate of 30 g/kg is considered the best application rate of alum because of its positive effects on plant dry matter. Our study clearly demonstrates that alum has potential as a soil amendment to increase plant growth; however, more research is needed to determine beneficial and / or detrimental aspects of this practice under field conditions.