APPLYING BIOSOLIDS: ISSUES FOR VIRGINIA AGRICULTURE

Finally, Page pointed out that most biosolids contain more than enough P to meet crop needs when applied
at rates calculated to meet crop N needs. Thus, P should be the controlling nutrient, not N, on sites with
already high or excessive soil P levels as indicated by soil tests. Under these conditions, the soil essentially
becomes saturated with P and any surplus can be transported off-site by surface runoff or leached into
the water table. Research currently being conducted compares the mobility of P in biosolids with P in
manures and commercial fertilizers. Early results indicate that P in biosolids is less mobile than P in
manures or fertilizers (Evanylo, 2000).

SUMMARY

Sludge is an end product of modern wastewater treatment. Increases in the number of people served by
sewer systems will inevitably increase the amount of sewage that must be disposed of in some way. The
added treatment needed to produce biosolids so that farmers may make use of it makes a lot of sense.
Using biosolids reduces farm production costs and can have beneficial soil effects. Recycling biosolids
on agricultural lands also reduces the cost of disposal to the public. Biosolids applied on farms typically
costs public authorities $18 to $25 per ton of semi-dry material while disposal at landfill sites typically
costs between $39 and $115 per ton of semi-dry material (telephone interviews).

However, no matter how logical the use of biosolids is for agricultural land, it will not work if applicators
do not pay attention to the detail of the regulations. Neither will it work if farmers do not know their soils
and appropriate agronomic practices. Farmers and biosolids applicators must work together for the
results to be beneficial to everyone.

Application laws and procedural requirements for biosolids give Virginia farmers a framework for utilizing
a valuable agronomic resource at little or no cost. Carefully coordinated biosolids applications on farms
where soils, slopes, and cropping sequence conditions are well matched to take advantage of the beneficial
effects, can result in on-farm benefits that far exceed the associated costs. Furthermore, if properly
applied, the potential environmental damage is less from biosolids than from commercial fertilizers.

³ Virtually is used because Class A treatment kills pathogens below levels detectable with current technology.

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