Effects of irrigation and fertilization practice on soil nematode communities in arable land

Abstract

Nematodes, with functional groups at all trophic levels, play a key role in soil food webs. Their community structure allows to assign food web conditions and soil health, e.g. to address management impact on arable land. A field experiment was set up near Potsdam (Brandenburg, north-east Germany) to investigate the effects of different fertilization and irrigation regimes on the nematode fauna and the micro-food web in a sandy soil. At an arable site cropped with potatoes the following treatments were established in a randomized plot design: surface, drip and no irrigation, combined with/without fertilization. Additionally, fertigated plots (simultaneous application of fertilizer in dissolved drip irrigation water) with/without crops were investigated. Soil samples were collected during one vegetation period in June, July and August. The nematode community structure was determined and a faunal analysis performed resulting in: Maturity Index (MI), Plant Parasite Index (PPI), Channel Index (CI), Enrichment Index (EI), Structure Index (SI) and metabolic footprints (F). In addition, phospholipid fatty acids were determined to identify microbial community structure and biomass. In August, surface irrigation resulted in a higher MI (i.e. lower disturbance) at unfertilized compared to fertilized plots. Furthermore, the fertigated plots showed a higher MI with crops than without. The PPI increased over time, while the CI indicated higher fungal decomposition at dryer conditions in August. The EI points to moderately enriched nutrient conditions, which was underlined by a high metabolic footprint of bacterial feeders. The structure and enrichment footprint showed that the stability of the micro-food web increased with time, indicating a positive influence of crop growth. In sum, effects of irrigation practice on the nematode community were apparent, while no response to the different fertilizer treatments was detected.