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The food specificity of nematodes, their high number of species and high abundance in every habitat where decomposition takes place, indicate that the structure of the nematode assemblage has a high information content. Since nematodes respond quickly to changes in soil management and since the nematode fauna can be efficiently analysed, the structure of the nematode assemblage offers an interesting instrument to assess changes in soil conditions. We studied the effect of five organic amendments on the short-term nematode population dynamics and compared them to minerally fertilised and unfertilised plots. The experiment was started in 2005, and samples were taken in spring and autumn 2006 and spring 2007. In spring 2006, no clear differences among treatments in the diversity of free-living nematodes were observed, probably since the organic amendments were applied only twice, of which the last application was carried out 7 months before the sampling. At the second and third sampling, the enrichment index in the organically amended plots was higher than in the unamended plots, owing to the organic matter application. However, in plots amended with farmyard manure and cattle slurry the number of bacterivores increased significantly, while in the compost plots the fungivorous nematodes tended to be higher. This resulted in a low channel index for the manure and slurry plots, indicating a predominant bacterial decomposition pathway, and a higher channel index in the compost plots, suggesting a greater proportion of fungal decomposition. These assumptions on the decomposition of the applied organic matter were strongly supported by the composition of the soil microbial community, determined through PLFA analysis: in the compost plots the bacteria to fungi ratio was lower than in the manure and slurry plots. At all sampling occasions there was a remarkably lower abundance of plant-parasitic nematodes in plots amended with slurry and manure, indicating a negative impact of both amendments on plant-parasitic nematodes. We can conclude from this study that the fertiliser regimes affected the nematode assemblage, but that more samplings in the future are certainly necessary to assess adequately the impact of the different organic amendments.

Summary We conducted a replicated field plot experiment to investigate the influence of five exogenous organic materials (farmyard manure, cattle slurry and three types of compost), as well as mineral fertilization and two unfertilized control treatments (with and without a crop) on the number, biomass and species composition of earthworms (Lumbricidae) in an arable soil. A crucial feature of the experimental design was that the same mass of exogenous organic C was applied in each of the five organic treatments (1500–4000 kg C ha −1 ), making it possible to interpret observed effects in terms of the quality of the organic amendments. Earthworms were sampled twice per year using a combination of mustard extraction and handsorting. Two and a half years after the first of four organic matter applications, the farmyard manure and cattle slurry treatments had the largest earthworm abundance of about 800–900 individuals m −2 with 120–140 g biomass m −2 . The unamended controls had the smallest earthworm number (about 150 individuals m −2 ), while the three compost treatments had intermediate values (400–500 individuals m −2 ). Since the mass of exogenous organic C applied was the same in the five organic treatments and since final soil organic C contents under these treatments were statistically similar ( p >0.05), we hypothesize that the observed large differences in earthworm abundance between the farmyard manure and cattle slurry treatments on the one hand and the three compost treatments on the other hand were caused by differences in the chemical properties, and hence nutritional value for earthworms, of the applied amendments. We propose that manure and slurry provided earthworms with larger amounts of available C sources for direct consumption (including polysaccharides and proteinaceous materials) than the composted organic materials which were more humified and stabilized as a result of extended microbial aerobic degradation.

We examined the short-term effect of five organic amendments and compared them to plots fertilized with inorganic fertilizer and unfertilized plots on aggregate stability and hydraulic conductivity, and on the OC and ON distribution in physically separated SOM fractions. After less than 1 year, the addition of organic amendments significantly increased (P < 0.01) the aggregate stability and hydraulic conductivity. The stability index ranged between 0.97 and 1.76 and the hydraulic conductivity between 1.23 and 2.80 · 10 )3 m ⁄ s for the plots receiving organic amendments, compared with 0.34– 0.43, and 0.42–0.64 · 10 )3 m ⁄ s, respectively, for the unamended plots. There were significant differences between the organic amendments (P < 0.01), although these results were not unequivocal for both soil physical parameters. The total OC and ON content were significantly increased (P < 0.05) by only two applications of organic fertilizers: between 1.10 and 1.51% OC for the amended plots versus 0.98–1.08% for the unamended and between 0.092 and 0.131% ON versus 0.092–0.098% respectively. The amount of OC and ON in the free particulate organic matter fraction was also significantly increased (P < 0.05), but there were no significant differences (P < 0.05) in the OC and ON content in the POM occluded in micro-aggregates and in the silt + clay-sized organic matter fraction. The results showed that even in less than 1 year pronounced effects on soil physical properties and on the distribution of OC and ON in the SOM fractions occurred.

In the scope of the increasing concern for soil conservation, reduced tillage (RT) agriculture is growing more important in today’s agriculture in Western Europe. However, crop rotations often include beets and potatoes, crops that are generally assumed to be less suitable under RT agriculture because they result in a high disturbance of the soil at the formation of the ridges and at harvest. Therefore, the short- and long-term effect of RT agriculture on bulk density (BD), water retention curve (WRC), aggregate stability and field-saturated hydraulic conductivity of silt loam soils with crop rotations including root crops was evaluated. Ten fields at seven locations representing the important RT types, applied for a different number of years, and eight fields under conventional tillage (CT) agriculture with similar soil type and crop rotation were selected. At each location, BD of the 5–10 cm layer was mostly lower in the RT fields (1.42 � 0.05 Mg m � 3 [average with

Compost and other organic amendments have been proven to improve the soil physical quality. In Flanders, vegetable, fruit and garden (VFG) wastes are collected selectively and composted. We studied the effects of the combined application of three different doses of VFG compost and cattle slurry and one treatment with only mineral N applied, during 9 years on a range of soil physical properties: aggregate stability, saturated hydraulic conductivity, bulk density, total pore volume and soil moisture retention. The organic amendments had a significantly beneficial impact (p

On a field experiment, started in spring 2005, we examined the influence of different types or qualities of exogenous organic matter (farmyard manure, cattle slurry and three different types of compost, compared with mineral fertilization, and two unfertilized treatments, cropped and uncropped) on the earthworm density and biomass. Earthworms were sampled with mustard powder and subsequent handsorting at the start of the experiment and one year (i.e. two organic matter applications) later. The organic matter applications had a significant effect on the earthworm populations. Earthworm abundance was highest on all organically amended plots, while the lowest number and biomass was found on plots without fertilization. On the latter earthworm number and biomass were equal to or lower than the initial situation. The highest earthworm biomass was recorded on plots amended with farmyard manure. There were indications too that the presence of a crop and the crop performance have an effect on the earthworm populations.

In Flanders, vegetable, fruit and garden (VFG) wastes are collected selectively and composted. We studied the effects of the combined application of three different doses of VFG compost and cattle slurry during 7 years on maize dry matter yields and three soil faunal groups: nematodes, micro-arthropods (springtails and mites) and earthworms. Combined application of VFG compost and slurry resulted in the highest yields. Initially, there was a clear yield depression on plots amended with compost in contrast to an upward trend in the last application years, proving a significant residual N effect from cumulative compost applications. The plant parasitic nematodes Pratylenchus sp. and the Tylenchidae were less abundant on plots receiving organic amendments, while the population of the bacteriophagous Rhabditidae was higher on these plots. Adding organic amendments resulted in increased numbers of micro-arthropods, springtails as well as mites. Earthworms were significantly more abundant when organic amendments were applied. The VFG compost had a larger overall positive effect on the three soil faunal groups than cattle slurry.