Horizon A gives the anthropological load, Horizon B the pedological load and Horizon C the geological background load. KUNTZE: The metal concentrations in Horizon B usually vary, decreasing with depth, so if analyses are made at small increments of depth, say 5 cm, this will give an indication of the pedological processes and the geological background. In FRG we use both limits but mostly the Recommended value. Have you any comment? This is one way of coping with the problem. Centre de Recherches de Bordeaux B. P content of plants was always decreased by sewage sludge application.
Concentrations of most heavy metals decreased with ageing of plants. Cd, Zn and, at minor extent, Cu appear as the most available metal originating from sewage sludge. Sewage sludge application reduced Fe and Mn availability. The findings of the study indicated also that Cd and Ni uptakes were likely dependent of each other.
The field experiments were located in an experimental farm of I. Treatments Treatments consisted of mineral fertilized check plots A and sludge amended plots B and C treatments.
Mineral fertilizers were added to adjust the total N-P-K-Ca and Mg content of soil at the same level il all plots. Experimental design Each plot was replicated five times in a randomized complete block design. The areas treated with sludge and fertilizer were 3, 0 m by 6, 0 m. The Cd and Ni content of this sludge was excessively high because a battery factory rejected his wastes in the treatment plant. The same element were measured in the grain.
Levels of significance were determined using the Bonferroni test. However in , as shown in Fig. Sewage sludge application induced a strong decrease in P uptake even in the case of the smaller rate Table 4. Concentration of most heavy metals decreased with ageing plants Table 5. This decrease in heavy metal concentration is likely due to a dilution effect, as well as the poorly metal enriched subsoil colonization by roots.
Table 6 Heavy metal availability in aerial parts of maize plants 1 Metal concentr. This would suggest either an antagonistic effect excersed by other metal or an immobilization of Mn and Fe resulting from organic matter enrichment or a pH increase. Tables 7 and 8. In the year following the high rate sewage sludge application, a rapid decrease of Zn content was observed but Zn tended to increase in the course of time.
Thus, at opposite of Zn, Mn availability tended to decrease or was not changed in the course of time Fig. Plots fertilized with Louis Fargue sewage sludge The most striking feature concerns Cd and Ni availability. As evidenced in Fig. This feature was specially displayed in : indeed a strong increase in Ni uptake was observed this year, whereas in the same time Cd uptake was reduced despite of the very high rate of metal addition through sludge application.
The low soil temperature prevailing in the first stage of maize growth in likely explains Cd and Ni behaviour. Possibly Cd uptake was depressed by low temperature level in rooting zone whereas Ni uptake was less affected bringing a strong decrease in maize yield. Only cold environment of roots prevailing during spring induced a strong depressive effect on maize yield, resulting probably from an increase in Ni toxicity. This findings of this study strongly indicates that more research is needed for estimating physiological process involved in: — heavy metal uptake and translocation in plants grown in nutrient medium containing several metals; 19 — temperature effect on the first stage of heavy metals uptake by plants.
Until adequate knowledge become available, use of chemical extractants to predict metal uptake would be made with caution.
Sol, 3, — Effect of heavy application of sewage sludge with high content of Cd and Ni on a continuous maize crop. First Europ Symp. Effect of heavy application of sewage sludge with very high content of Cd and Ni on lettuce and maize crops. Second Europ. Factors influencing heavy metal availability in field experiments with sewage sludges. Elsevier appl. In the treatment where t of sludge was applied per ha, approximatley 30 t of lime would have been added to the soil.
How did this affect the soil pH and organic content? How do these compare with the sludge normally utilised on land in France? JUSTE: The sludge was from the vicinity of a battery manufacturing factory, and this would not normally be applied to land. Should this be taken into account with soil pH change? JUSTE: In this experiment soil moisture content was maintained constant on all plots by irrigation, so the sludge had no effect on the overall moisture content of the soil.
Can you explain this? Soil temperature affects nutrient availability and plant growth. Most heavy metals form insoluble phosphates which may worsen phosphorus deficiency. In the cold north area of FRG, liquid phosphate is applied to maize crops to counteract the deficiency.
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I do not think there was a phosphorus deficiency. The problem was not formation of insoluble phosphates, but physiological effects due to metal toxicity reducing phosphorus uptake. There are differences in cultivar response. Increasing amount of sludge increased the Zn content in plants markedly and regular. In a field experiment, 28 different crops were grown in 0, 10 incorporated and 40 cm decomposed sludge.
The heavy metal content varied greatly from crop to crop. Different parts of the plant contained different amounts of the various elements. In a pot experiment increasing temperatures resulted in higher content of Mn, Fe, Zn and Cd, while the content of Ni, Cu and Mo were little influenced. Extra applications of metals to soil through sludge is more doubtful if the strain from other sources e. There can be large variations between districts as regards this strain. Although there are differences in the farming managements, the types of crops grown and the heavy metal strain in different countries, there is probably little basis for such great differences in the guidelines for sludge utilization.
Even if the problem in Norway may be different from the problems in other countries, the above mentioned investigations may serve as a basis for a more general discussion of the problem.
The magnitude of the experimental data may, however, restrict reference in short and simple term. Sludge for agricultural purpose For agricultural purpose 16 field experiments with increasing applications of sludge were carried out. Most of the trials lasted for 2 growing seasons and results from 28 harvests are refered here. Lime treated sludge is excluded. The main crop was cereal but grass and fodder rape have also been used in some of the experiments.
Analyses for heavy metals were carried out on yield from plots without sludge but with N-fertilizer and plots with sludge but without N. These were compared. The content of heavy metal in sludge used in the trials can be characterized as low but representative.
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The relative figures for each sludge amount was calculated based on just the same experiments with control treatments. Table 1. Numbers of experiment harvests in brackets. Sludge, tons DM per hectare Cd Pb Zn Ni Cu Mn Fe 0 15 20 45 60 65 3 97 2 4 89 4 92 4 3 2 91 6 93 3 11 11 11 5 3 93 14 99 2 18 99 16 18 12 8 7 1 8 8 8 4 1 10 12 11 12 7 96 2 Sludge application has, only to a little degree changed the Cd-content of the plants while the content of Pb was practically unchanged.
The Zn amounts in the plants have been greatly increased by increased sludge applications but the levels were scarcely phytotoxic. This was observed in 2 experiments in the first year. This can partly be attributed to the decline in pH upon sludge application, but this pH effect lasted for only one year.
Mn and Cu levels in the plants were continuously raised by increasing sludge doses. Crop response to sludge application was somewhat greater for meadow grasses and rape than for cereal grains. Trials with different crops grown on 0, 10 and 40 cm decomposed sludge Green areas commonly require higher applications of sludge compost than agricultural land. Our trials indicate that a 4—10 cm layer is adequate. As our experiments on the use of sludge on agricultural land indicated that the metal content in yields, except for Zn, is changed within a certain margin of error, it was considered necessary to lay out our present trials using high rates viz: 0, 10 and 40 cm layers of decomposed sludge.
The 10 cm layer was incorporated into the top 20 cm of the soil.
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Altogether 28 crops were grown for each treatment. Some of the crops were grown for 3 years, some for 2 and some for only 1 year. During the first summer a drop in the pH in pure sludge to 5.
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Even though a rise in the pH was later recorded in sludge and sludge-treated soils, this never reached the pH level of the top soil without sludge. Cd, Fig. The Cd-content in different plants and different parts of the plants differed greatly.