Metal residues in soils previously treated with sewage- sludge and their effects on growth and nitrogen fixation by blue-green algae.

A - Papers appearing in refereed journals

Brookes, P. C., McGrath, S. P. and Heijnen, C. 1986. Metal residues in soils previously treated with sewage- sludge and their effects on growth and nitrogen fixation by blue-green algae. Soil Biology and Biochemistry. 18 (4), pp. 345-353.

AuthorsBrookes, P. C., McGrath, S. P. and Heijnen, C.
Abstract

Nitrogen-fixation was measured in illuminated laboratory incubations of soils containing different concentrations of Zn, Cu, Ni and Cd. The soils were taken from field experiments that had received either farmyard manure (low-metal soils) between 1942–67 or metal-contaminated sewage-sludge (high-metal soils) between 1942–61 so that the last metal inputs from sewage-sludge were more than 20 years ago.

Colonies of blue-green algae (cyanobacteria) and other microorganisms developed rapidly on the surface of low-metal soil and after a 14 day lag there was a rapid increase in rate of C2H2-reduction, indicative of N2-fixation. C2H2-reduction reached a maximum rate after about 28 days then slowly declined. In contrast, colonisation of the surface of high-metal soil was very much poorer. C2H2-reduction only commenced after 50 days, reaching only about a third of the rate in the low-metal soil by 118 days, when the experiment ended.

In another experiment the low-metal soil fixed about 10 times as much 15N-labelled N2 as the high-metal soil. The ratio C2H2 reduced-to-N2 fixed was 5.

Measurements of total C2H2-reduction were made during a 60 day incubation on soils sampled on a transect from the middle of a low-metal farmyard manure (FYM) plot to the middle of a high-metal sludge plot. There was a negative correlation (r = −0.78) between total C2H2-reduction and increasing distance along the transect, corresponding to increasing soil concentrations of Zn, Cu, Ni and Cd with increasing distance. Total C2H2-reduction was decreased by 50% at about 50 μg EDTA-extractable Zn, 20 μg Cu, 2.5 μg Ni and 3 μg total Cd g−1 soil. Because the amounts of metals in the soils were closely correlated with each other there was a similar relationship with Zinc Equivalent. At half the current permitted U.K. metal loading based on Zinc Equivalent, C2H2-reduction was also decreased by about 50%.

Year of Publication1986
JournalSoil Biology and Biochemistry
Journal citation18 (4), pp. 345-353
Digital Object Identifier (DOI)doi:10.1016/0038-0717(86)90037-4
Open accessPublished as non-open access
Output statusPublished
Publication dates
Online10 Dec 2002
Publication process dates
Accepted06 Mar 1986
PublisherElsevier
Copyright licensePublisher copyright
ISSN0038-0717

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