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In the Netherlands soil biological measurements are undertaken in a nationwide monitoring programme. The measurements are combined in the Biological Indicator of Soil Quality (BISQ). About 300 locations were selected in a random stratified design comprising stringent combinations of land use and soil type. All locations were sampled in a six-year cycle. In this contribution we describe the monitoring network and the BISQ and present average values for biomass, abundances and taxonomic diversity of various soil dwelling organisms derived from 10 years of measurements. We further highlight some results and discuss the possibilities in soil and land management policy frameworks for improving sustainable land management. [ABSTRACT FROM AUTHOR]

There is considerable concern in Europe that soil organic matter (SOM) contents are declining, which would threaten both agriculture and the environment. We performed a trend analysis of SOM contents in sandy soils, using historic data from routine agricultural soil analyses. Data were selected from grass, grass-maize rotation and maize fields in four adjacent provinces that had been sampled four to five times during the period 1984–2004. Absolute (at least 1%) and relative changes (SOMt=20/SOMt=0) were calculated and regressed against initial SOM contents. Mean SOM content showed a north-south gradient per cropping system. We found no single uniform trend in SOM contents for any of the three systems. Over the 20-year period, SOM declined in c. 25% of all grasslands, amounting to 185 000 of the 635 000 hectares of land under grass and forage crops in the four provinces, and increased in a total of 267 000 hectares. Carbon accumulation in grassland sandy soils was calculated at 39 g C m−2 year−1 (top 5 cm). For the grasslands, initial SOM contents were linearly and negatively related to absolute changes in SOM; the relation with the relative change was best explained by using log-transformed values of SOM. We conclude that in grassland soils in the Netherlands, conservation of SOM requires identification of high-risk fields rather than high-risk areas. For continuous maize on sandy soils, the entire area may be denoted as high-risk, because all fields could reach the critical limit of 3.4% SOM in the near future. [ABSTRACT FROM AUTHOR]

Summary 1 We examined the effects of plant-feeding nematodes on competition between Holcus lanatus and Anthoxanthum odoratum . In the Drentse A nature reserve, the Netherlands, a relatively productive grassland, represented by H. lanatus , has gradually been replaced by a less-productive community, represented by A. odoratum , after the application of fertiliser was stopped. Stressed plants are generally considered to be more sensitive to herbivory. 2 We hypothesized that plant-feeding nematodes would exacerbate the competitive disadvantage of H. lanatus resulting from nutrient limitation. We compared performance in an adjusted De Wit replacement series with monocultures, grown in soil that was either treated or untreated with nematicides at both low and high nutrient supply. 3 The biomass production of both plant species was negatively affected by intra- and interspecific competition. Although H. lanatus was a stronger competitor than A. odoratum in mixed cultures, it was more sensitive to plant-feeding nematodes and nutrient limitation. Nematodes and nutrient stress therefore reduced the competitive suppression of A. odoratum by H. lanatus . Low nutrient availability did not enhance the effect of plant-feeding nematodes on plant growth and competition, indicating additive rather than synergistic effects on plant performance. 4 We conclude that plant-feeding nematodes may contribute to species replacements in grasslands after fertilization has been stopped, albeit to a lesser extent than reduced nutrient availability. Plant species-specific differences in tolerance to plant-feeding nematodes in general, rather than host specificity of nematodes, are responsible for any effects. [ABSTRACT FROM AUTHOR]

On request of the Dutch government a committee of the Health Council of the Netherlands has reviewed the role that results of field research in its broadest sense (i.e., including multi-species toxicity tests in the laboratory, research on model ecosystems et cetera) can play in ecotoxicological risk assessment for the authorisation of pesticides. The Committee believes that field research can provide valuable additional data about the exposure of non-target organisms and the resultant effects at population, community and ecosystem level. However, it frequently is unclear how these data might be used in reaching a decision about authorisation. To solve this problem, it is necessary to specify what is understood by "unacceptable damage". Both more clearly formulated protection goals of the government and a better understanding of the ecological significance of effects are needed to clarify this. Furthermore, the Committee points out that the statistical power of field trials must be sufficient to allow for the detection of changes that might be regarded as ecologically relevant. Finally, it recommends keeping a finger on the pulse in relation to authorised pesticides by monitoring their presence in environmental compartments and by investigating their role in suddenly occurring mortality among conspicuous animal species, such as birds, fish and honeybees. This kind of research forms a safety net for substances that have been wrongly authorised.