No abstract

Four field sites which have been irrigated with various levels of secondary treated sewage effluent for 9 to 11 years have been examined for phosphorus content in soil water extracted with suction lysimeters. The cornfield site on Hublersburg clay loam irrigated with effluent had an average P concentration of 0.329, 0.070, and 0.046 mg/liter in soil water at 15, 60, and 120 cm respectively compared to 0.043, 0.046, and 0.037 mg/liter, respectively, under an adjacent fertilized, but unirrigated control. Year round application of effluent including 2 years of effluent plus sludge to reed canarygrass (Phalaris arundinacea L.) on Hublersburg clay loam resulted in average soil water concentrations of 0.170, 0.100, and 0.052 mg P/liter at 15, 60, and 120 cm, respectively. In an abandoned field on Hublersburg clay loam where no P was removed by crops, P concentrations were 0.140, 0.103, and 0.076 mg P/liter for the treated plot and 0.038, 0.047, and 0.042 mg P/liter for the control at 15, 60, and 120 cm, respectively. Only the 15‐cm depth had significantly higher P concentrations in the treated plot. A hardwood forest located on a Morrison sandy loam soil was irrigated year round. Phosphorus concentrations in soil water were 0.349, 0.080, and 0.087 mg/liter for the treated vs. 0.059, 0.039, and 0.039 for the control at 15, 60, and 120 cm, respectively. Leaching losses were calculated from concentration of P in soil water at 120 cm and from leaching volume which was rainfall plus irrigation minus potential evapotranspiration. Over all years of treatment no site had leaching losses of > 3% of the total applied.

Plots in a mixed hardwood forest received two separate applications of anaerobically digested sewage sludge (0.102–3.094% solids) in fall 1974 and spring 1975. Total solids loading in the low and high treatments were 12.71 and 26.96 metric tons/ha, respectively. Copper, Zn, and Cd loadings in the high treatment were 24.50, 28.49, and 0.253 kg/ha, respectively. Calculated amounts of percolate Cu, Zn, and Cd moving out of the 120‐cm depth in the high treatment were 0.3, 3.2, and 6.6% of the total applied levels, respectively, indicating the order of relative mobility in soil as Cd > Zn > Cu. Relative levels of 0.1/V HCl extractable vs. total soil Cu, Zn, and Cd sampled before and after sludge applications indicated that Cu applied in the sewage sludge was more extractable than the native soil Cu, Zn was only slightly more extractable, and Cd was less extractable. Of the other heavy metals (Cr, Pb, Co, and Ni) analyzed in 0.1/V HCl soil extracts, only Cr and Ni increased in the 0‐ to 7.5‐cm depth following sludge applications.

Synopsis Eight soils in sand‐soil‐peat mixtures reacted differently to compaction as reflected in percolation rates and aeration porosity. Generally, if the mixtures contained 50% or less total sand, compaction at high moisture contents resulted in inadequate percolation rates. Mixtures containing 70% total sand maintained adequate percolation rates under compaction but the average available moisture content of such mixtures was only 1.2 inches per foot of depth.

Time‐dependent batch equilibrium studies for Cu, Zn, and Cd were conducted to determine the sorbing properties for these metals on the upper 30 cm of a forest soil. Major cations were added to equilibrating solutions in an attempt to match to cationic matrix of a sewage sludge. Essentially all of the Cu was adsorbed by the soil in the first 0.3 hour of equilibration. Copper adsorption data fit the Freundlich isotherm better than the Langmuir isotherm. Adsorption of Zn and Cd was more time dependent than Cu, especially for the 0–7.5 cm depth of soil, and was described with some success by the empirical kinetic equation, ∂S/∂t = aCbSc, where S is µg metal absorbed per g soil, C is concentration of metal in final equilibrating solution, t is time, and a, b, and c are constants. Batch data taken at 3 hours of equilibration for Zn and Cd also fit the Freundlich isotherm better than the Langmuir isotherm. For Cu, Zn, and Cd adsorption, Freundlich constants (K) were higher for the 0–7.5 cm depth than for the 7.5–15 cm depth, indicating the binding effects of the higher level of organic matter in the surface 7.5 cm of forest soil.