tected, but only in a few plots in the field.
Species composition
No difference was found between Mix and No-mix treatments within strips. Although the plots differed in species composition, nematode abundances were not significantly influenced by this. This was possibly due to the fact that the experiment only started in 2014 and differences in soil condition, soil biota, fertility, etc. (if there were any) didn’t have the time to evolve yet. Expected is an increase in differences between Mix and No-mix plots over time. This is because those treatments (Mix as more diverse and No-mix as less diverse) will be implemented on every crop sown in the future on these plots.
Strip 6 had a more diverse Mix treatment than Strip 1 (as indicated in table 1). Effects of this more diverse grass-clover mixture are assumed to be negligible, for the difference between Mix and No-mix was insignificant and the sown species mixture of strip 6 had less time to establish than strip 1.
Total nematodes
The data on total nematode abundance obtained from counting and performing a Q-PCR differed with approximately a factor 10, the question rises whether both data-sets are representing reality. In this study, the data obtained from counting nematodes under the microscope do most likely represent reality better than data obtained from the Q-PCR. This is because less errors could be made in the counting method. The samples were well shaken while 5 mL suspension was taken. Possible explanations for the large difference in nematode numbers between the two quantification methods, are pipetting errors during dilution of samples, or a possible lack of shaking of PCR samples during pipetting. In both scenario’s, less nematodes are possibly transferred into the final Q-PCR tubes than assumed. Although the data cannot represent reality quantitatively, the data within a method can be used as relative values, for the samples are all treated in the same way.
As stated in the results, nematode abundances in the 2 year old grass-clover mixture were shown to be higher than in the one year old mixture. This was significant in both count data and Q-PCR data.
Organic matter content
The field is relatively heterogeneous considering organic matter (OM) content. Expected was to find a relation between OM and fungivorous nematode abundances [15]. However, no correlation exists between Aphelenchoididae or total nematode abundance and organic matter content, according to the results. Possible explanations could be the influence of factors such as Mix/No-mix treatment, water availability or compaction of the soil.
Conclusions
The most important finding is the increase of total nematode abundance in the two year old grass-clover crop. More time since tilling had the effect of increasing nematode numbers. The hypothesis that nematodes are more abundant in perennial crops, rather than annual crops is supported. However, more support is needed from other research on different nematode genera to confirm this hypothesis.
The diversity in species composition had no effect on nematode abundance, so other annual and perennial agricultural systems have to further examine the use of diverse crop mixtures for nematode communities.
Finally, the conclusion can be made that we indeed can manage soil life. This study shows, however, that links in (agro) ecological systems are not easy to predict and changes in crop diversity or soil conditions are not always linearly correlated with soil life. From former research, is clear that by changing aboveground diversity, e.g. by diversifying the cropping system, you could change belowground soil biota [4]. Mechanisms behind these
