There is no such thing as a natural soil free of metals. Agronomic rates Applying biosolids at the proper application rate that satisfies crop yield goals reduces the risk of excessive non-essential elements. Agronomic rates are tied to the nitrogen needs of the crop. As with nitrogen fertilizer, the farmer sets a yield goal. The goal determines the nitrogen rate.
Formulas convert the biosolids analysis into the quantity of available N per dry ton.
The factors change for different biosolids. For example, assume you wish to grow 4 tons of grass hay per acre. If the biosolids have 3 percent N per dry ton, then they have 60 pounds N per ton. The biosolids supplier can provide laboratory analysis of the material produced by the treatment plant. Apply this application rate to other elements in the material.