Municipal sewage sludges, or biosolids, can be applied to croplands to supply and recycle nutrients and organic C. Trace elements in sludges, however, may be of environmental concern. This study examines the long‐term consequences to crops and soil when loading phytotoxic levels of one or more trace elements to cropland. Municipal sewage sludges containing trace elements, including high concentrations of Cd, Cr, Cu, Pb, Ni, and Zn, were applied to cropland from 1977 to 1986 at three rates plus an untreated control. Plant and soil samples were collected between 1985 and 1990. These results report on yield and metal uptake of corn (Zea mays L.), sorghum‐sudangrass (Sorghum bicolor L. Moench × S. sudanese P. Stapf.), and soybean (Glycine max L.). Yields of all crops were reduced on one or more sludge treatments because of phytotoxic concentrations of soil trace elements, probably Zn and Ni. Phytotoxicity has continued since the last sludge application. Chemical fractionation of surface soils was performed using a sequential extraction technique and trace elements were measured in each of eight fractions. Cadmium, Ni, and Zn occupied soil fractions that were potentially available for plant uptake. Copper and Cr loadings increased the environmental availability of these two elements to a smaller extent. Loadings of Pb to the levels seen in this study did not appear to significantly increase its environmental availability. The Toxicity Characteristic Leaching Procedure (TCLP) and guidelines used to characterize hazardous wastes were inappropriate to use when testing soils for potential phytotoxic concentrations of trace elements or uptake of these elements into the food chain.
Retention of As against extraction by NH4OAc and Bray P‐1 reagents from Wisconsin soils equilibrated with As (0, 80, and 320 µg As/g added as Na2HAsO4) increased as the sesquioxide content increased. Similarly, the amount of As sorbed from solution increased as the free Fe2O3 content of the soils increased. Removal of amorphous Fe and Al components by treatment with oxalate eliminated or appreciably reduced the As sorption capacity of the soil. Amorphous Fe and Al components preferentially sorbed added As, as evidenced by the quantitative removal of added As from equilibrated soils by a single oxalate extraction and the essentially complete recovery of added As by NH4F and NaOH reagents during chemical fractionation. Because As released during extraction with NH4F is sorbed by soil components during the same extraction, NH4F‐As is underestimated unless a correction for resorption is made.
Excessive soluble P in runoff is a common cause of eutrophication in fresh waters. Evidence indicates that drinking water treatment residuals (WTRs) can reduce soluble P concentrations in P-impacted soils in the short term (days to weeks). The long-term (years) stability of WTR-immobilized P has been inferred, but validating field data are scarce. This research was undertaken at two Michigan field sites with a history of heavy manure applications to study the longevity of alum-based WTR (Al-WTR) effects on P solubility over time (7.5 yr). At both sites, amendment with Al-WTR reduced water-soluble P (WSP) concentration by >or=60% as compared to the control plots, and the Al-WTR-immobilized P (WTR-P) remained stable 7.5 yr after Al-WTR application. Rainfall simulation techniques were utilized to investigate P losses in runoff and leachate from surface soils of the field sites at 7.5 yr after Al-WTR application. At both sites, amendment with Al-WTR reduced dissolved P and bioavailable P (BAP) by >50% as compared to the control plots, showing that WTR-immobilized P remained nonlabile even 7.5 yr after Al-WTR amendment. Thus, WTR-immobilized P would not be expected to dissolve into runoff and leachate to contaminate surface waters or groundwater. Even if WTR-P is lost via erosion to surface waters, the bioavailability of the immobilized P should be minimal and should have negligible effects on water quality. However, if the WTR particles are destroyed by extreme conditions, P loss to water could pose a eutrophication risk.
Agreement Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the USDA or the Mississippi Agricultural and Forestry Experiment Station and does not imply its approval to the exclusion of other products that may also be suitable.
In a field study, sodium arsenite, which is used widely in Wisconsin as a defoliant for potatoes, was applied to a Plainfield sand at rates ranging from 45 to 720 kg As/ha. The plots were planted to potatoes in 1967; peas, snap beans, and sweet corn in 1968; and to peas in 1969. Yields of potatoes were greater than check at the 45 and 90 kg As/ha rates, but decreased to 79 and 24% of check yield at the high As rates. Snap bean and sweet corn yields also decreased with increasing As, and no growth was obtained on the high As plots. The As content of above‐ground portions of potatoes varied widely, and bore no relationship to As treatment. Evidence of As contamination by windblown As‐treated soil was obtained. Arsenic was below detectable limits in edible portions of peas and sweet corn, but up to 0.5 ppm of As accumulated in potato tubers and up to 84 ppm in potato peelings. Detectable levels of As occurred in snap beans, with up to 1 ppm As accumulating in snap bean seeds and pods from the 180 kg As/ha plots. Yield decreases were related highly to total, 1 N NH4OAc extractable and Bray P‐l extractable As. The data suggest that, with the Plainfield sand, marked yield reductions of peas, snap beans, and sweet corn occur at about 10, 1, and 5 ppm of total,N NH4OAc, or Bray P‐l extractable As, respectively. The finding that yield reductions and As contamination of vegetable crops will occur indicates that use of As as a potato vine defoliant on sandy soils should be discouraged.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.