EFFECTS OF CROP ROTATIONS OF CEREALS WITH VETCH AND FALLOW ON SOIL NEMATOFAUNA IN CENTRAL SPAIN

The influence of the use of vetch or fallow in rotation with cereals o n the dynamics of nematode populations was studied in a field experime nt conducted on a luvisol in Central Spain. All the nematodes present in the trial were monitored by seasonal samplings for three consecutiv e years, starting one year after the first rotation cycle was complete d. Vetch in rotation with cereals controlled sail populations of some virus transmitters (Xiphinema pachtaicum and Trichodorus sp.) and the cyst nematode Heterodera avenae. Fallow also controlled X. pachtaicum and H. avenae, as well as Pratylenchus thornei, Ditylenchus dipsaci, T ylenchorhynchus maximus and Tylenchus sp. Other Dorylaimidae and Rhabd itidae species seemed to be influenced by vetch and fallow only indire ctly. Neither rotation influenced Longidorus profundorum populations. The maturity index based on the nematode fauna was used as a measure o f the disturbance in this ecosystem.