The bionomics of soil nematodes in Manitoba soils

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Kimpinski, Joe Thomas
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Fifty-one genera of nematodes were found in three types of soil in southern Manitoba. Butlerius spp., Leptonchus spp., and Pseudhalenchus spp. were newly recorded in Canada. Helicotylenchus spp., Tylenchorhynchus spp., Tylenchus spp., Mesorhabditis spp., Panagrolaimus spp., and Eudorylaimus spp., were the most numerous. Clay soils harbored greater numbers of nematodes than sand. Plot A (17.2% sand, 42.8% silt, 40.0% clay) harbored 43 genera, plot B (94.4% sand, 2.7% silt, 2.9% clay) harbored 37 genera, and plot C (21.7% sand, 42.6% silt, 35.7% clay) had 36 genera. Differences in numbers of nematodes between the three plots were correlated with differences of nitrogen (N), potassium (K) and soluble salts in the soil solution, and not to soil type. In pot experiments, nematode populations in clay and sand under grass were exposed to different levels of N, phosphorus (P) and K. The number of nematodes was greater in clay than in sand, but the difference may have been due to greater plant growth in clay. The number of nematodes decreased as N content in clay increased, whereas nematode numbers increased with the addition of N to the sand. Numbers of dorylaimids were similar in clay and sand. They decreased in number as N treatments were increased from 0 ppm to 600 ppm. Dorylaimids were most numerous at 0 ppm N with 40/400 ppm P/K ratio levels, and 200 ppm N with 20/200 ppm P/K ratio levels. Tylenchids were more numerous in clay than in sand, and decreased as N treatments were increased in clay. In sand, tylenchids increased in number with higher N treatments. Numbers of non-stylet bearing (NSB) nematodes were similar in clay and sand, but probably would have been more numerous in sand if vegetation had been the same in both soils. Increased N levels produced no change in NSB populations in clay, but were correlated with larger populations in sand. Nematode biomass was greater in clay than in sand, but the difference may have been due to the different vegetative content of the two soils. Biomass was greatest in sand at 200 ppm of N, and in clay at 0 ppm of N. Biomass decreased steadily with increased N treatments.