Water treatment residuals for ameliorating sandy soils: Implications in environmental, soil and plant growth parameters

Water treatment residuals (WTR) application may improve the quality of sandy soils; however, nutrient deficiency to plants and potentially toxic elements (PTEs) may be limiting. In contrast, adjusting the WTR pH, soil pH and WTR application rate might prevent adverse effects. This study aimed to evaluate the environmental safety and agronomic effectiveness of limed WTR for application in sandy soils. The tested treatments were increasing rates (0, 15, 30 and 60 Mg ha−1 of dry mass) of ground, dried and limed WTR in sandy soil under field conditions. Soil samples with disturbed and undisturbed structure were collected to determine selected soil physical, hydraulic and chemical parameters related to fertility, as well as the soil concentration of PTEs. Nutrients and PTEs content in plant tissue and the agronomic performance of maize and ryegrass were also evaluated. WTR were beneficial as they increased the content of fine and reactive particles (clay and silt). In general, WTR rates did not spoil soil chemical parameters related to soil fertility; did not increase aluminium saturation; and did not change soil PTE contents which were below the limits indicated by environmental legislations. The tested WTR rates did not cause negative effects on the agronomic variables of maize and ryegrass plants. Thus, waste application rates up to 30 Mg ha−1 are recommended. Liming WTR and soil makes this material safe and suitable for application in sandy and acidic agricultural soils.