The population density of six nematode genera was evaluated in an organic crop rotation of oats, Avena sativa, and rye, Secale cereale (winter); bush beans, Phaseolus vulgaris, (spring); soybean, Glycine max (summer); and broccoli, Brassica oleracea (fall) as a function of prior years in bahiagrass (Paspalum notatum) and tillage. Neither conventional nor conservation tillage significantly impacted nematode populations. Root-knot (Meloidogyne spp.), reniform (Rotylenchulus spp.), spiral (Heliocotylenchus spp.), stubby-root (Tricodorus and Paratrichodorous spp.), ring (Mesocriconema spp.), and dagger (Xiphinema spp.) nematodes were quantified from 2011 to 2013 in plots that had been previously in bahiagrass for 2 or 25 yr or where bahiagrass had not been grown. In 2011, root-knot nematode population density was low after the winter oats and rye cover crop regardless of whether the plots were in 0-, 2-, or 25-yr bahiagrass rotation. After the bush bean and soybean rotation, there was an increase in root-knot abundance in the 0-yr bahiagrass regime, compared to 2 or 25 yr in bahiagrass. Root-knot population density was low in the second and third year of the crop rotations. Reniform and spiral nematodes were often impacted by prior years in bahiagrass. The abundance of reniform nematodes was highest for the bush bean crop in the 0-yr bahiagrass treatment from 2011 to 2012. For soybeans, the abundance of reniform nematodes was much higher for 0-yr bahiagrass only during the first year of the study. Root-knot nematodes on broccoli remained at very low levels, and reniform nematodes were low except for 2011 in the 0-yr bahiagrass treatment. The influence of weed species on the population density of nematode genera was evaluated in the field. The populations of spiral nematodes were highest of the nematode genera in soil samples collected from the vicinity of the root systems of bahiagrass, bermudagrass (Cynodon dactylon), goosegrass (Eleusine indica), bush bean, purple nutsedge (Cyperus rotundus), smooth pigweed (Amaranthus hybridus), soybean, and tropical spiderwort (Commelina benghalensis). The population densities of other nematode genera in soil samples surrounding weeds were low.
