Properties of anaerobically digested and composted municipal solid waste assessed by integrating soil mesofauna manipulations and nutrient modelling

Summary

This study links the fields of nutrient mineralization and foodweb dynamics by investigating two types of fertilizers, anaerobically digested (ADMSW) and composted (CMSW) municipal waste. The fertilizers were amended to pots planted with barley and inclusion or exclusion of soil mesofauna (microarthropods and enchytraeids). There were four equidistant sampling occasions over a period of 113 days measuring mesofauna, plant N and biomass, soil N and ergosterol (fungal biomass). Soil respiratory quotients, soil mineral N, and contribution of ammonium N by the mesofauna were subsequently modelled
from parallel studies. Although plant N content at 113 days was significantly higher in ADMSW compared to
no fertilizer amendments the addition of fertilizers did not substantially increase plant growth. This was most likely due to N-limitation in the early stages of plant growth. According to the modelled data immobilized both fertilizers initially mineral N, and there was no net mineral N gain by the fertilizer amendments. Enchytraeid abundance was about three times higher in ADMSW than CMSW at 113 days indicating that ADMSW contained more labile compounds, bacteria and microfauna. Collembolan abundance was overall similar in
the two fertilizer treatments. The mesofauna presence did not affect plant growth or N-content in spite of that the total amounts of excreted ammonium by the mesofauna were modelled to be 12 % and 18 % compared to total plant N for ADMSW and CMSW, respectively. These values were based on a range of novel ammonium excretion rates for both microarthropods and enchytraeids.