Long-Term Dynamics of Nematode Communities in Arable Soil Under Four Cropping Systems

(1) The effects of the nematode fauna of four cropping systems were studied for 5 years in an experimental field in central Sweden. Plots were cropped as follows: barley with (B 120) and without (BO) nitrogen fertilization; grass (GL); and lucerne (LL). (2) The perennial crops had, on average, higher nematode densities (GL 8 7 and LL 9 8 x 106 m-2) than the annual crops (BO 5 6 and B120 6 8 x 106 m-2). Root production appeared to influence total nematode density. (3) The highest diversity of nematodes was found in GL, which differed in many respects from the other cropping systems. However, cropping practices were apparently of little importance in determining which species and genera were present in any particular plot. (4) Plant feeding species were most abundant in LL, while fungal feeders and omnivore/ predators were most abundant in GL. Bacterial feeders were more abundant than fungal feeders in B120 and LL. (5) In the perennial systems, the numbers of some taxa fluctuated strongly, while, in the annual systems, they remained stable throughout the experiment.