Integrating foodweb dynamics with nutrient and energy flows in soil amended municipal sorted waste

Summary

Few experimental studies have directly linked flux measurements and foodweb dynamics due to differences in traditions between agronomically and ecologically oriented laboratories. We decided to explore this gap in a study with amendments of fertilisers made from municipal sorted household waste (MSW).
Two types of fertilizers, degassed waste (DE) and compost (CO), were amended to pots planted with wheat and with and without soil mesofauna (microarthropods and enchytraeids). A treatment without amendments (NO) and fauna was used as a control. About three times as much CO than DE was added to the pots. There were four equidistant sampling occasions over a period of nearly four months (113 days) measuring mesofauna, plant biomass and ergosterol (fungal biomass). At day 57 and 113 plant N were measured as well as soil N at day 113. A parallel study was conducted with fertilizer amendments without plants measuring respiration and mineral N content.
In spite of having similar mineralization rates the respiration at day 29 was about twice as high in DE than CO. After day 29 the respiration rates was similar. The addition of fertilizers did in spite of an N-limited soil not increase plant growth although N content was significantly higher in DE than NO at day 113. Ergosterol was significantly higher in CO than DE at day 85 and 113. Mesofauna presence did not affect plant growth or N-content. Enchytraeid abundance was about three times more abundant in DE than CO at day 113 indicating that DE contained more labile compounds that the enchytraeids could feed on. Collembolan abundance was similar in the two fertilizer treatments. The collembolan community was in numbers dominated by Proisotoma minuta. The direct contribution of the soil mesofauna at day 113 was simulated to be 2.6%, 1.4%, and 1.5% of the total N mineralization for DE, CO and NO, respectively.