Collembola and mites in plots fertilised with different types of green manure

The spring and summer abundance of soil living mites and Collembola was inv estigated in organically grown field plots which had been covered with eith er the nitrogen catch crops winter rye, hairy vetch, fodder radish and a co ntrol (stubble). The catch crops were incorporated in the soil shortly befo re sowing of spring barley with undersown clover grass. Microarthropods wer e extracted from 10 cm deep soil samples and were taken in May, June and Au gust. The densities of both microarthropods were extremely high with up to 120,00 0 Collembola m(-2) and 90,000 mites m(-2). The highest densities of Collemb ola were found in the plots with fodder radish as a catch crop, and the mos t abundant species were Tullbergia sp., Isotoma notabilis and Folsomia fime taria. The mite fauna consisted mainly of Mesostigmatic and Prostigmatic mi tes and was more abundant in the catch crop plots than in the control plots in early June. The input of organic matter from the catch crops is supposed to be part of the reason for the high microarthropod densities, but the barley with under sown clover grass may also play a role.