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This article in JEQ

  1. Vol. 28 No. 5, p. 1644-1650
    Received: Aug 14, 1998

    * Corresponding author(s): ippolito@lamar.colostate.edu
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Co-Application Effects of Water Treatment Residuals and Biosolids on Two Range Grasses

  1. J. A. Ippolito *,
  2. K. A. Barbarick and
  3. E. F. Redente
  1. Dep. of Soil and Crop Sciences, Colorado State Univ., Fort Collins, CO, 80523,
    Dep. of Rangeland Ecosystem Science, Colorado State Univ., Fort Collins, CO, 80523.



Alum [Al2(SO4)314H2O] is commonly used in the municipal water treatment process to destabilize colloids for subsequent flocculation and water clarification. Water treatment residuals (WTR) can be classified as a waste material from these treatment plants. Concerns over land application of WTR are due to its postulated reduction of plant available P and potential plant Al toxicity with increasing WTR rates. Co-application of WTR with biosolids may benefit municipalities with biosolids inherently high in P concentrations and in terms of a cost savings by landfill avoidance. In a greenhouse study, we investigated the efficacy of co-application of WTR and biosolids to the native shortgrass prairie species blue grama (Bouteloua gracilis H.B.K. Lag) and western wheatgrass [Pascopyrum smithii (Rydb.) A. Love]. Our objectives were to quantify co-application effects on plant P and Al concentrations and uptake, biomass production, and WTR P adsorbing capacity. With blue grama, we observed a positive linear relationship between increasing WTR rate and yield and a negative linear relationship with increasing WTR rate and shoot P and Al concentration (P < 0.10). With western wheatgrass, increasing WTR rate produced a negative quadratic effect on shoot Al concentration (P < 0.10). Some investigators have observed P deficiency symptoms associated with WTR application; however, we did not. Our adsorption study indicated that co-mixing of the City of Fort Collins, CO, WTR and biosolids at ratios of 8:1 will adsorb all soluble biosolids P. Beyond this ratio the WTR could adsorb all biosolids available P and possibly some soil-borne P.

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