Uptake coefficients for biosolids-amended dryland winter wheat

Area of Science:

• Environmental Science
• Agronomy
• Soil Science

Background:

• Biosolids regulations use uptake coefficients (UCs) for risk assessment of elemental additions.
• UCs are assumed to be constants in current risk assessment models.
• The study investigates the variability of UCs with repeated biosolids application.

Purpose of the Study:

• To test the hypothesis that UCs for Cu, Fe, Mo, Ni, P, and Zn decrease with multiple biosolids applications.
• To evaluate the suitability of UCs as constants in risk assessments involving repeated biosolids amendments.
• To propose an alternative method for estimating element concentrations in wheat grain.

Main Methods:

• Applied biosolids to dryland winter wheat at two Colorado sites over 20 years (1993-2013).
• Collected data on grain elemental concentrations and biosolids application rates.
• Analyzed trends in UCs and cumulative element removal versus addition.

Main Results:

• Grain concentrations of six elements showed no trend with increasing biosolids applications.
• UCs for these elements followed exponential decay models, not constants.
• The slope between cumulative elemental removal and addition in grain provided a consistent value.

Conclusions:

• UCs are not constant under multiple biosolids applications, challenging current risk assessment models.
• A cumulative approach, analyzing element removal versus addition, offers a more stable estimation for risk assessment.
• This revised strategy may improve the accuracy of predicting wheat grain element concentrations from biosolids amendments.