Trace metal extractability in soils and uptake by bromegrass 20 years after sewage sludge application

Abstract

. 2002. Trace metal extractability in soils and uptake by bromegrass 20 years after sewage sludge application. Can. J. Soil Sci. 82: 323-333. The long-term potential for sewage sludge amendments to alter forage trace metal concentrations was determined on bromegrass, which received no sludge application for 20 yr following annual application during 1973-1980 on a no-till randomized-plot experimental site. In addition, soils were analyzed for trace metals, both total and extractable (using hot 0.01 M CaCl 2 ), by axial-view inductively coupled plasma spectrometry.For Cu, Ni, Zn and Cd, extractability from the soil (by CaCl 2) as well as plant tissue concentrations were relatively low considering the high loadings of these particular metals, a fact attributable to the near-neutral pH and high organic matter content of these calcareous soils. However, total and extractable soil Mo remained elevated in the sewage-sludge-amended plots above the levels measured in the fertilized control plots some 20 yr after the last sewage sludge application. Mo bioaccumulated in the bromegrass more than the other trace metals investigated at this site. The Cu:Mo ratio in the forage, a measure of potential to induce Cu deficiency in grazing ruminants, was substantially depressed by most of the sewage sludge treatments. Comparison of the 2000 and 1980 bromegrass analyses suggests an increase in the long-term plant availability of Mo in soils amended with highFe and high-Al sludges. Conversely, there was a long-term decrease in Mo availability on the high-Ca sludge treatment, consistent with evidence that much of the Mo has been lost from the topsoil since sludge application. For Cu, Ni and Zn, plant availability appears to have decreased between 1980 and 2000, attributable in part to a calculated loss of substantial fractions of these metals from the topsoil.Bromegrass concentrations of Cu, Ni, Zn, Cd and Mo were strongly correlated to CaCl 2 -extractable and total metals in the soils, indicating the utility of 0.01 M CaCl 2 in predicting plant availability. The chemical differences in the three sludge types applied at the site (high-Ca, high-Al, high-Fe) had little long-term impact on the extractability and phytoavailability of most trace metals remaining in the topsoil. Pour cela, ils ont examiné du brome cultivé sur des terres qui n'avaient pas été amendées avec des boues usées pendant 20 ans après en avoir reçu chaque année de 1973 à 1980. Les essais ont eu lieu sur un site expérimental constitué de parcelles randomisées dont le sol n'avait pas été travaillé. Les auteurs ont aussi déterminé la concentration totale et extractible (au CaCl 2 à 0,01 M chaud) d'oligo-éléments dans le sol à partir des incidences axiales obtenues par spectrométrie à plasma inductif. La quantité de Cu, de Ni, de Zn et de Cd extraite du sol (au CaCl 2 ) et la concentration de ces oligo-éléments dans les tissus végétaux sont relativement faibles malgré la grande quantité de boues usées épandues. On le doit sans doute au pH presque neutre et à la forte con...

Surface-Applied Biosolids Enhance Soil Organic Carbon and Nitrogen Stocks but Have Contrasting Effects on Soil Physical Quality

“…In contrast, Gaskin et al [26] reported that SOC levels were not different between bermudagrass fields receiving repeated surface applications for <6 yr or for >6 yr, though SOC levels in both treatments were higher than unamended fields. Longterm gains in SOC have been reported in other studies which found that increased SOC or SOM levels can persist up to 27 yr after biosolids applications have ceased [24,25,29,[34][35][36].…”

“…Other field studies on repeated surface-applied biosolids also have found increases in SOC [4,12,[24][25][26][27]29] and found that increases are positively correlated with application rate [4,25]. Site-specific increases in SOC have been reported for application rates as low as 2 to 7 Mg ha −1 yr −1 [24,30].…”

Balance and forms of zinc in soil and its uptake by plants

“…Důležitým výsledkem je potvrzení v literatuře prezentovaného předpokladu, že vysoký celkový obsah zinku v půdě nemusí automaticky znamenat vysoké obsahy v pěstovaných rostlinách (McBride et Evans, 2002;Schaecke et al, 2002). Jedinou výjimkou byly poměrně vysoké koncentrace ve špenátu.…”

“…Ukazuje to na vysokou srovnatelnost výsledků dosahovaných s použitím těchto vyluhovadel. Zcela v souladu s literárními prameny (Chander et Brookes, 1993;Guang Wen et al, 2002;McBride et Evans, 2002) je potvrzen efekt použitých kalů (půda Chrlice) na zvýšení podílů méně stabilních (potenciálně mobilizovatelných) frakcí zinku v půdě. Ačkoli celkový obsah není extrémně vysoký, téměř čtvrti-na je vyluhovatelná roztokem DTPA.…”

“…U půdy z Kutné hory je to pouze něco přes 5 %. Vzhledem k tomu, že vstup do rostlin sice byl poněkud zvýšený, avšak nikoli mimořádný, lze souhlasit i s dalším poznatkem z literatury (Schaecke et al, 2002;Guang Wen et al, 2002;McBride et Evans, 2002), že aplikace vysokých dávek zinku do kvalitních půd vede k částečné imobilizaci zinku do méně přijatelných forem. Půdy s vyš-ším pH tak lépe chrání produkci před kontaminací.…”