Use of Two Industrial Wastes as Soil Amendments: Effect on Dissolved Reactive Phosphorus in Runoff

Abstract

To control the dissolved reactive phosphorus (DRP) concentration in a soil solution, a number of soil amendments were tested. In the current study, Blast Furnace Slag (BFS) and Water Treatment Residues (WTR) were tested on bare soil under two rainfall intensities and two soil roughness levels. The soil was fertilized with P (KH₂PO₄) at a rate of 400 kg ha⁻¹ while BFS and WTR were applied at a rate of 5 g per 100 g of soil. Two soil roughness levels were exposed to artificial rainfall intensities of 30 and 65 mm h⁻¹. Three rainfall events were performed on each treatment. The runoff water generated over an area of 0.5 m² with a slope of 8% was collected at different time intervals and analyzed for DRP, Al, Fe, and K concentrations. The results showed that, regardless of rainfall intensity and soil roughness, the concentration of DRP in the runoff water increased with increasing runoff time from the unamended plots. However, in the BFS- and WTR-amended soils, the DRP concentration decreased with runoff time. Dissolved reactive P and DRP loads were the lowest from the WTR-amended plots, followed by the control and the BFS treatment plots. Water treatment residues reduced the mean DRP concentration by 27.3% and the DRP load by 32% compared to unamended plots. The two rainfall intensities significantly affected the DRP concentration and load. Under the low rainfall intensity, the DRP concentration and load were higher compared to the high rainfall intensity. The overall DRP concentration was not affected by changes in soil roughness. However, the DRP loads were higher from the plots with low soil roughness levels, especially during the first and second runs. Both the BFS and WTR were also effective in reducing the DRP concentrations in the drain water collected during the runoff events. The concentrations of Al, Fe, and K in the runoff water were not affected by the soil amendments. However, the electrical conductivity and pH readings were higher from the BFS-amended plots.

Keywords:

• Dissolved reactive phosphorus
• simulated rainfall intensity
• soil roughness
• blast furnace slag
• water treatment residues

Acknowledgements

The authors would like to thank the Japan Society for the Promotion of Science (JSPS) for providing the grant to conduct this study. Thanks are also due to the Kyo-ritsu Company, Hiroshima, Japan, for providing the WTR and Professor K. Hattori, Faculty of Agriculture, Tottori University, for providing the BFS.

Notes

^†EC = Electrical conductivity; TC = Total carbon; TN = Total nitrogen; Oxl = Oxalate extracted.

*Significant at the 0.05 probability level.

  **Significant at the 0.01 probability level.

  ***Significant at the 0.001 probability level.

  ^†SE = Standard error.

  ^‡LSR = Low soil roughness; HSR = High soil roughness.

  ^§WTR = Water treatment residues; BFS = Blast furnace slag.

^†LSR = Low soil roughness; HSR = High soil roughness; WTR = Water treatment residues; BFS = Blast furnace slag.