The self-regulatory potential of agro-ecosystems: Using nematodes as indicators for legume disease suppressive soils
Final Report Abstract
Nematodes are widely used indicators of soil fertility thereby serving the current need to identify agricultural management options to develop regenerative land-use systems. However, attempts to predict soil disease suppressiveness with the help of nematodes failed so far. Reasons were a.o. that short-term experiments do not consider soil building processes, a lack of nematode bioindicators, and the lack of links to crop yield and disease parameters. We made use of two organic long-term experiments (LTEs) of the University of Kassel in order to identify nematodes associated with disease suppressive soil and to determine appropriate cover crops that foster these species. Treatments applied in the LTEs were noninversion tillage combined with rye-vetch mulch application to potatoes versus plough tillage (25 cm, without mulch) as well as mineral (rock phosphate, potassium sulfate) versus compost fertilization. Soils were analyzed for nutrients and the nematode community (WP1). The soils’ potential to suppress the root-lesion nematode Pratylenchus penetrans (WP2), three pea root rot pathogens (WP3), and the potential of cover crops (Vicia sativa, Raphanus sativus, Avena strigosa) to foster indicators of soil suppressiveness in selected soils of the LTEs (WP4) was studied in greenhouse experiments. Soil fertility, determined by increased field pea yields as well as increased macronutrient and organic carbon levels, was greater in non-inversion tillage soils compared to ploughing. Furthermore, in non-inversion tillage systems, root rot disease severities in field pea (-10%) were lower while the number of Pratylenchus per gram of root varied from (-6% (LTE 1) - +24% (LTE 2)) compared to ploughed soils. Independent of these effects, the nematode metabolic footprint, which describes the carbon that is channeled through the total nematode community, negatively correlated with the disease severity due to soil borne fungi (r=-0.78, p<0.001) and the number of Pratylenchus per gram root (r=-0.62, p=0.001). In the last experiment, cover cropping of Vicia sativa resulted in the highest metabolic footprint (1053 µg C/ 100 ml soil) while it was significantly lower after growing Raphanus sativus (577 µg C/ 100 ml soil). In conclusion, the nematode metabolic footprint appeared as a useful indicator of suppressiveness towards soil borne pathogens of pea. Growing Vicia sativa as cover crop showed much potential for improvement of soil suppressiveness. Field studies are further needed in order to confirm the usefulness of metabolic footprints as indicator of disease suppressiveness in complex cropping sequences as well as for other soil borne diseases.
Publications
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Bacterivorous Nematodes Correlate with Soil Fertility and Improved Crop Production in an Organic Minimum Tillage System. Sustainability, 12(17), 6730.
Schmidt, Jan H.; Hallmann, Johannes & Finckh, Maria R.
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Developing Organic Minimum Tillage Farming Systems for Central and Northern European Conditions. No-till Farming Systems for Sustainable Agriculture, 173-192. Springer International Publishing.
Junge, Stephan M.; Storch, Johannes; Finckh, Maria R. & Schmidt, Jan H.
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Nematode-based indices correlate with soil fertility in two organic long-term field experiments. Presented at the ESN’s Virtual Nematology Conference 2021 from May 26 th to May 28th.
Schmidt, J.H., Finckh, M.R., Theisgen, L.V., Kanfra, X., Heuer, H. & Hallmann, J.
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Pflanzengesundheit richtig managen. Ökologie & Landbau 199, 41–43.
Finckh, M.R., Baresel, J.P., Junge, S.M., Šišić, A., Weedon, O.D. & Schmidt, J.H.
