Long-term dynamics of nematode communities in arable soil under four cropping systems.
The nematode fauna of 4 cropping systems were studied for 5 years in central Sweden. Plots were cropped as follows: barley with (B120) and without (BO) nitrogen fertilization, grass (GL) and lucerne (LL). The perennial crops had on average higher nematode densities (GL 8.7 and LL 9.8×106 m-2) than the annual crops (BO 5.6 and B120 6.8×106m-2). The highest diversity of nematodes was found in GL, which differed in many respects from the other cropping systems. However cropping practices were of little importance in determining which species and genera were present in any particular plot. Plant feeding species were most abundant in LL (41%) and least abundant in BO (17%). More fungal feeders were found in BO (35%) and GL (31%) than in the other 2 cropping systems (16 - 18%). The bacterial feeders were dominant in B120 (45%) and least dominant in GL (33%). The proportion of omnivore/predators did not vary much between treatments (6-8%). In the perennial systems the numbers of some taxa fluctuated strongly, while in the annual systems they remained stable.