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Title: Brassicaceous and rye cover crops altered free-living soil nematode community composition

item WEIL, RAY
item Zasada, Inga

Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2010
Publication Date: 5/1/2010
Citation: Stocking, L.A., Weil, R., Zasada, I.A., Momen, B., Sardanelli, S. 2010. Brassicaceous and rye cover crops altered free-living soil nematode community composition. Applied Soil Ecology. 45:1-12.

Interpretive Summary: Cover crops are plants grown at a time when the primary crop of interest is not grown. Cover crops have many positive attributes; they provide ground cover thereby reducing erosion, produce nitrogen thereby decreasing the need for nitrogen fertilizers, and may control pests such as microscopic worms called nematodes. Brassica cover crops (radish and rapeseed) are gaining popularity as a cover crop in the Mid-Atlantic coastal plain due to the multiple benefits provided to farmers. One problem with using cover crops is that their effects on non-pest organisms are poorly known. Therefore, scientists monitored pest and beneficial nematode communities after growing the brassica cover crops. We found that not only did soil nematode communities respond differently to brassica cover crops, but they also responded differently depending on when the cover crop was killed. The results are significant because they provide insights on how to manage cover crops to achieve pest suppression but minimize non-target effects. Consequently, the results will be used by scientists developing more effective and sustainable strategies involving brassica cover crops to control nematodes.

Technical Abstract: Nematode community analysis was utilized to evaluate the biofumigant or allelopathic effects of brassicaceous and rye winter cover crops on non-target nematodes in three experiments in Maryland. Nematode response parameters were genus, family, trophic group population density, and percentage distribution of trophic groups in the entire nematode community divided into colonizer-persister ranks. Cover crops had unique impacts on nematode communities, but these impacts appeared to be associated more with quality of organic matter inputs rather than biofumigation or allelopathy. Across all dates and seasons, and four to nine months after winter-kill, dormant bacterivore (dauer larvae) nematode populations in the forage radish (C/N shoots ~ 10) plots ranged from 3.5 to 15.7 times higher (P < 0.10) than in the control plots. Plant-associate (Tylenchidae) nematodes were 4-6.5 times higher (P<0.10) in rapeseed or rye (C/N shoots ~ 25) plots compared to the control in June of two experiments. Correlations of nematode community groups with cover crop and soil parameters suggested that dauer larvae abundance was associated with soil moisture in radish plots, and tissue quality and quantity at the time of cover crop termination was associated with nematode community response. Overall, results suggest that radishes stimulated a bacterial decomposition pathway, while rapeseed and rye stimulated a proportionally greater fungal-based food web.