Mobility and uptake of zinc, cadmium, nickel, and lead in sludge-amended soils planted to dryland maize and irrigated maize-oat rotation

Sludge application to agricultural lands is often limited mainly because of concerns about metal accumulation in soils and uptake by crops. The objective of the study was to test the following hypotheses: (i) in the short to medium term (5-10 yr), the application of good-quality sludge according to crop N requirements will not lead to significant accumulation of water-soluble metal fractions in soil, (ii) mobility and uptake of metals is higher under irrigated than dryland systems, and (iii) metal concentrations in plant tissue could reach phytotoxic levels before the soil reaches environmental threshold levels. Field plots were arranged in a randomized complete block design comprising four replications of three treatments (0, 8, and 16 Mg ha yr anaerobically digested municipal sludge) planted to dryland maize and irrigated maize-oat rotation. Soil and plant samples were collected after 7 yr of treatment application for selected metal analyses. A large fraction of the Zn, Ni, and Pb in the soil profile was ethylenediaminetetraacetic acid extractable (46-79%). Saturated paste-extractable fractions of Cd and Pb were <1 mg kg. Plant uptake of Cd, Pb, and Ni under irrigation was double that for dryland systems. Concentrations of the metals considered in plant tissue of both cropping systems remained well below phytotoxic levels, except for Zn under dryland maize, which received 16 Mg sludge ha yr. Metal concentrations in the soil remained far below total maximum threshold levels. Therefore, hypotheses 1 and 3 were accepted for the metals considered, and hypothesis 2 was rejected for Zn.

Leaf and seed micronutrient accumulation in soybean cultivars in response to integrated organic and chemical fertilizers application

Plant nutrients can be influenced by organic materials of soils. An experiment was conducted to evaluate the effect of organic amendments on elements uptake by soybean cultivars in a silty loam soil in Mazandaran province, Iran. The experiment was carried out in split plot based on randomized complete block design with three replications in 2006. Main plots were included 8 fertilizer treatments consisted of 20 and 40 Mg ha(-1) Municipal Solid Waste Compost (MSW), Vermicompost (VC) and Sewage Sludge (SS) which enriched with 50% chemical fertilizers needed by soil, only chemical fertilizer treatment and control. Sub plots consisted of three genotypes of soybean (032, 033 and JK). Grain yield was determined and soybean leaves and seeds were digested and analyzed for Mn, Cu, Zn and Fe. Results showed that yield and elements content in soybean leaves and seeds (Mn, Cu, Zn and Fe) were influenced by all treatments. The 40 Mg ha(-1) of sewage sludge enriched with chemical fertilizers produced maximum grain yield. Different soybean cultivars had also significant differences in terms of leaf and seed micronutrients accumulation. Maximum grain yield was observed in JK and 033. Mean comparisons showed that interaction effects of fertilizer and cultivar had significant differences on Mn, Cu and Fe content in soybean leaves, so that the maximum Cu content was observed in 032 cultivars with 40 Mg ha(-1) enriched sewage sludge and municipal waste compost. Also the highest amount of Fe was obtained for JK cultivar when the 40 Mg ha(-1) of municipal compost was used. Among different mentioned traits, Fe and Cu content in leaf and seed and Zn content in leaf had a positive and significant correlation with grain yield.

Evaluation of sewage sludge, septic waste and sludge compost applications to corn and forage: Ca, Mg, S, Fe, Mn, Cu, Zn and B content of crops and soils

This is the second of two papers presenting the data from an experiment on the application of aerobically-digested sewage sludge (AES), anaerobic lagoon septic wastes (ANS), sewage sludge compost and fertilizer to soils for grass forage and feed corn production at two different sites in Nova Scotia. Crop yields, plant tissue and Mehlich-1 extractable soil nutrients were evaluated; 15 elements were analyzed in the plant tissue and 9 elements in the soil extracts. This paper describes the Ca, Mg, S, Fe, Mn, Cu, Zn and B content of the crops and the Mehlich-1 extractable content of the soils. The response to the amendments was not consistent at the two sites with the two different crops. We found that the septic sludge (ANS) produced the highest forage Fe, Cu and Zn levels and was equal to compost in elevating corn stover and forage S and the forage B content. The compost produced the highest forage Ca and corn Zn, the AES produced the highest corn Mn, and fertilizer produced the highest forage Mn. None of the amendments produced excessive levels of the above nutrients; rather, the amendments improved the feed quality of the forage and corn stover. Lastly, it was noted that the Mehlich-1 extract only had a significantly positive correlation with forage Cu content.

Biological and ecophysiological reactions of white wall rocket (Diplotaxis erucoides L.) grown on sewage sludge compost

We studied the effects of sewage sludge compost on white wall rocket (Diplotaxis erucoides L.) compared with mineral fertilization and control (without any fertilizer) in a greenhouse experiment. The plants grown on the compost-amended soil showed a different growth dynamic: a significant delay in flowering and a bigger root system. Both the compost and the fertilization treatments increased biomass and seed yield. Heavy metal (Cu, Cd, Zn, Ni) distribution within the plant was in the following order: roots > leaves > stems, except for zinc which was homogeneously distributed. The balance of mineral nutrition was not affected by treatments. Zinc was the trace element which was most taken up. Unlike many species of Brassicaceae, white wall rocket is not a hyperaccumulator. Although sewage sludge compost improved plant growth, delay in flowering shows that it is necessary to take precautions when spreading sewage sludge in natural areas.

Contrasting effects of sewage sludge and commercial fertilizer on egg to adult development of two herbivorous insect species

Municipal sewage sludge containing heavy metals had a toxic effect on the development of the cabbage looper, Trichoplusia ni (Lepidoptera: Noctuidae), one of two herbivorous insects commonly found in an Ohio old-field which had been subjected to long-term sewage sludge application. Soils were removed in 1992 from an old-field following 11 years of heavy nutrient enrichment (1978 to 1988) with applications of either sewage sludge (Milorganite(®)) containing heavy metal contaminants or urea-phosphate fertilizer. Egg to adult development rate and survival of the blackfaced leafhopper, Graminella nigrifrons (Homoptera: Cicadellidae), and the cabbage looper was determined on maize (leafhopper) and broccoli (looper) seedlings grown in soils from sludge-treated, fertilizer-treated, or untreated control plots of the old-field. Fertilizer and sludgetreated soils had higher levels of N. P and organic matter, and a lower pH than the untreated control soils, while sludge-treated soils contained significantly higher concentrations of Cd, Cu, Pb, and Zn. Maize appeared to be unaffected by the three soil treatments, and survival and rate of egg to adult development of the leafhopper was not affected. Broccoli seedlings grown in both the high nutrient fertilizer and sludge soils were greener and larger than broccoli grown in control soils. However, the cabbage looper had significant larval and pupal mortality (25 to 40%) and prolonged egg to adult development on sludge-grown broccoli compared to control and fertilizer treatments. As assimilation into the food chain of heavy metals and other organic pollutants, such as PCBs, is in part a function of the interaction of soil chemistry and type of plant, the application of municipal sludges to old-fields needs to be carefully monitored, as contaminants may have significant developmental and behavioural effects on some secondary links in the old-field food chain.