Soluble As levels were determined in flooded soils and found to be related to the total As content and the reduced environment obtained. The flooded soils equilibrated at 25C contained a soluble As concentration which ranged from 0.06 to 0.18 ppm when treated with 0.568 mg of As/100 g soil, applied to the soil as NaAsO2. No appreciable As was found in the samples equilibrated at 25C which had not been treated with As. The equilibration of samples at 38C resulted in much higher concentrations of soluble As. The concentration of soluble As ranged from 0.15 ppm for a sample with no added As to 0.79 ppm for a sample which received 1.135 mg of As/100 g of soil. A reduced environment resulted in a greater soluble As concentration. Samples equilibrated at 38C were more reduced than those equilibrated at 25C. The increase in soluble As at lower reduction potentials was attributed to the reduction of Fe and not the reduction of As itself. Arsine was not detected in any of the soil samples.

Arsenic toxicity levels for ‘Lankert’ cotton (Gossypium hirsutum L.) and ‘Patterson’ soybeans (Glycine max L. merr.) were determined in a green house experiment using an Amarillo fine sandy loam and a Houston Black clay. The treatments ranged from 28 to 280 kg As/ha in the Amarillo soil and from 56 to 560 kg As/ha in the Houston Black soil. The vegetative cotton yields were significantly decreased below the checks at the 56 and 280 kg/ha rates of applied As in the Amarillo and Houston Black soils, respectively. Soybeans were found to be more sensitive to As than cotton. Vegetative soybean yields were significantly decreased at the applied rates of 28 kg As/ha in the Amarillo soil and 168 kg As/ha in the Houston Black soil. Yield limiting As concentrations in plant tissue were 4.4 ppm and greater in cotton, and 1 ppm and greater in soybeans. Water soluble As levels of 8 ppm in the Amarillo soil and 28 ppm in the Houston Black soil were required for a significant decrease in the vegetative growth of cotton. The water soluble As levels detrimental to soybeans were 3 and 12 ppm in the Amarillo and Houston Black soils, respectively.

Field experiments were conducted to determine the residue levels of propanil (3′,4′‐dichloropropionanilide), DCA (3,4‐dichloroaniline), and TCAB (3,3′,4,4′‐tetrachloroazobenzene) in the flood water and Beaumont clay soil under normal rice (Oryza sativa L.) cultivation. Propanil applied as a foliar spray at 3.4 and 6.8 kg/ha 24 hours before flooding was dissipated from the flood water within 24 hours following the flood. The amount of propanil dissipated corresponded to the DCA concentration in the flood water at 24 hours, indicative of biological degradation of propanil to DCA. TCAB was never detected in other than trace quantities. Neither propanil nor its metabolites were detected in soil samples collected at 2.5–5.0 cm and 17.5–20.0 cm below the surface 24 hours following the application of the flood water.

A continuous flow soil respirometer was used to evaluate the effect of nutrient addition, application rate, and application frequency on biodegradation of 2 complex oily sludges in soil. The most rapid biodegradation of the refinery sludge occurred when nitrogen was added to reduce the carbon to nitrogen (C∶N) ratio to 9∶1. The petrochemical sludge was degraded most rapidly when nitrogen, phosphorus, and potassium were added at a rate of 124∶1, C∶NPK; CO2evolution from both wastes increased with increasing application rates, but the fraction of applied sludge which degraded decreased with increasing application rates. Small frequent applications resulted in a slight increase in respiration rate per unit applied over a single equivalent application, indicating that repeated applications of smaller amounts of sludge result in a more rapid rate of decomposition. The population of total soil bacteria was greatest when 1% of either sludge was added to the soil, whereas 5 and 10% sludge additions resulted in slightly lower microbial populations.

The land disposal of municipal liquid digested sludge by surface application to a growing forage crop may cause foliage to become coated with sludge. The ingestion of foliage contaminated with sludge could be detrimental to the health of grazing animals, since municipal sludges often contain potentially toxic amounts of various heavy metals. The influence of simulated rainfall, leaf morphology, and sludge solids concentration on the retention of sludge heavy metals by the foliage of grasses was evaluated.Liquid digested sludges, containing 2 and 4% solids, were applied to greenhouse flats of common bermudagrass (Cynodon dactylon L.) and Bell rhodesgrass (Chloris gayana Kunth.), equivalent to depths of 2.50 and 1.25 cm, respectively. Sludge‐treated grasses were subjected to simulated rainfall equivalent to 2.5 cm/hour either immediately following sludge treatments or after 24 hours of drying. Additional flats receiving the sludge treatments were sampled at regular intervals over a 2‐week period to determine the foliar retention of sludge in the absence of rainfall.The foliage of both grasses was visibly contaminated with sludge following application. The foliar concentrations of Cd, Cu, Pb, and Zn were measured for each sludge treatment. There appeared to be no preferential retention of any particular heavy metal. Bell rhodesgrass retained more sludge than common bermudagrass because of its larger leaf blades and overlapping sheathes. The sludge containing 4% solids was retained by the foliage to a greater extent than sludge containing 2% solids.Sludge that was not allowed to dry on the leaves was removed by 1.25 cm of simulated rainfall, regardless of the grass species or sludge solids concentration. Sludge that was allowed to dry on the leaves, however, was not removed by 2.50 cm of simualted rainfall.