H Synthetic organic compounds

When dealing with municipal sludge, one other constraint to application rates should be addressed. Most sludge has synthetic organic compounds, such as chlorinated hydrocarbon pesticides, which can be slow to decompose and may be of concern from a human or animal health standpoint.

Polychlorinated biphenyls are in many sludges. Federal regulations require soil incorporation of any sludge that has more than 10 ppm of polychlorinated biphenyls wherever animal feed crops are grown. Polychlorinated biphenyls are not taken up by plants, but can adhere to plant surfaces and be ingested by animals and humans when the contaminated plant parts are eaten. Pesticide uptake by crops is minimal, and concentrations in wastes would be much less than that typically and intentionally applied to control pests on most cropland (USEPA 1983).

Table 6-2 Recommended cumulative soil test limits for metals of major concern applied to agricultural cropland1 (USEPA 1983)

Metal ------Soil cation-exchange capacity, meq/100g2 3

lb/ac (kg/ha)

Pb

500 (560)

1,000 (1,120)

2,000 (2,240)

Zn

250 (280)

500 (560)

1,000 (1,120)

Cu

125 (140)

250 (280)

500 (560)

Ni

125 (140)

250 (280)

500 (560)

Cd

4.4 (5)

8.9 (10)

17.8 (20)

1 Table 6-2 values should not be used as definitive guidelines for fruit and vegetable production.

2 Interpolation should be used to obtain values in CEC range 5-15.

3 Soil plow layer must be maintained at pH 6.5 or above at time of each sludge application.

1 Table 6-2 values should not be used as definitive guidelines for fruit and vegetable production.

2 Interpolation should be used to obtain values in CEC range 5-15.

3 Soil plow layer must be maintained at pH 6.5 or above at time of each sludge application.

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