Mikrobiologisch-ökotoxikologische Bodenuntersuchungen von zwei zur Unkrautbekämpfung mit hohen Dosierungen eingesetzten Fettsäure-Herbiziden

Goal and Scope

Products based on fatty acids (including acetic acid) are known in plant protection since more than 100 years to control several harmful organisms. In the following decades, however, they lost their importance due to the rapid development of ‘modern’ chemical pesticides. In the meantime some trials were run to control weeds with relatively high doses. The knowledge on its ecotoxic effects on soil microorganisms as a part of the soil fertility, however, is still incomplete.

Methods

Under laboratory conditions two agricultural soils were treated with different dosages of two products based on acetic acid and pelargonic acid (=nonanoic acid) as well as with a biocidal reference compound (e.g. dinitrophenol herbicide). The applied dosages were related to the concentrations in soil reached after simulated penetration of practical field amounts into upper soil layers. In some cases green manuring was simulated by adding lucerne meal to the soil. During the incubation for several weeks biomass-related microbial activities (dehydrogenase activity, substrate-induced shortterm respiration) as well as the mineralization of carbon and nitrogen (including nitrification) were measured.

Results and Conclusion

As compared to ‘normal’ pesticides (e.g. the reference compound) the effects of both test substances on soil microorganisms showed different behaviour. Nearly none of the effects typical for strongly biocidal compounds, namely a dose-related inhibition of microbial biomass combined with a stimulated mineralization (especially of nitrogen), occurred with the fatty acid products. Depending on the marked input of organic carbon by the higher dosages of fatty acid products and their rapid decomposition, especially of acetic acid, an increase of biomass-related parameters and of carbon mineralization combined with a reduction of the available nitrate content (e.g biological nitrogen immobilization) occurred for several weeks. By combining the results of the soil with that of lucerne meal-amended soil ‘real effects’ can be distinguished from those depending on the decomposition of the introduced carbon. In comparison with the strongly biocidal reference compound the two fatty acid products not only caused little microbiological-ecotoxicological impacts on the soil, but often stimulated important microbiological parameters for some time.

Recommendation and Perspective

As result of the trials we recommend an extended microbiological-ecotoxicological test spectrum especially for those plant protection products (pesticides) which should be applied at high dosages or if they contain higher amounts of well decomposable organic substances. This is necessary to distinguish dose-related enhanced biocidal activities induced by biocidal effects (including the subsequent mineralization of the killed microorganisms) from ‘real’ stimulations directly produced by the substrate.     

Automatic construction of concept hierarchies: The case of foliage-dwelling spiders

In this paper, we present the hierarchical variable dependencies that were obtained from raw data with the use of two machine learning techniques on an ecological data set. The data set contains features of field margins and the corresponding number of spider species inhabiting them. This data set was used before by domain experts to construct a fuzzy qualitative model with hierarchical variable dependencies, which we use for comparison with our results. One of the machine learning methods constructs a hierarchical structure similar to the one in the experts’ model, while revealing some additional interesting relations of environmental features with respect to the number of spider species. The other method constructs a different hierarchy from the one proposed by the experts, which, according to our classification performance experiments, might be even more appropriate.     

When does nitrate become a risk for humans?

Is nitrate harmful to humans? Are the current limits for nitrate concentration in drinking water justified by science? There is substantial disagreement among scientists over the interpretation of evidence on the issue. There are two main health issues: the linkage between nitrate and (i) infant methaemoglobinaemia, also known as blue baby syndrome, and (ii) cancers of the digestive tract. The evidence for nitrate as a cause of these serious diseases remains controversial. On one hand there is evidence that shows there is no clear association between nitrate in drinking water and the two main health issues with which it has been linked, and there is even evidence emerging of a possible benefit of nitrate in cardiovascular health. There is also evidence of nitrate intake giving protection against infections such as gastroenteritis. Some scientists suggest that there is sufficient evidence for increasing the permitted concentration of nitrate in drinking water without increasing risks to human health. However, subgroups within a population may be more susceptible than others to the adverse health effects of nitrate. Moreover, individuals with increased rates of endogenous formation of carcinogenic N-nitroso compounds are likely to be susceptible to the development of cancers in the digestive system. Given the lack of consensus, there is an urgent need for a comprehensive, independent study to determine whether the current nitrate limit for drinking water is scientifically justified or whether it could safely be raised.     

Impact of using paper mill sludge for surface-mine reclamation on runoff water quality and plant growth

Paper mills generate large amounts of solid waste consisting of fibrous cellulose, clay, and lime. Paper mill sludge (PMS) can improve reclamation of surface-coal mines where low pH and organic-carbon levels in the spoil cover material can inhibit revegetation. When applied at high rates, however, PMS may adversely impact the quality of surface runoff. Therefore, we applied PMS at 0, 224, and 672 dry Mg ha(-)(1) to 22.1 x 4.6-m plots at a recently mined site and monitored runoff for a total of 13 mo. The zero-rate plots served as controls and received standard reclamation consisting of mulching with hay and fertilization at planting. Compared to the control plots, PMS reduced runoff fourfold to sixfold and decreased erosion from 47 Mg ha(-1) to <1 Mg ha(-1). Most of the reduction occurred in the 2.5 mo before the plots were planted. Flow-weighted average dissolved oxygen concentrations in runoff from plots at the 224 and 672 Mg ha(-1) rates, however, were much lower (相似文献   

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