Stijn van den Bergh

Process technologies, such as composting, anaerobic digestion, or lactic acid fermentation, greatly influence the resulting organic amendments (OAs) characteristics even when the same raw material is used. However, it is still unclear how these process technologies indirectly modify the effect of OAs on soil microbial activity and soil aggregation. To determine the effect of OA produced using pre-treatment technologies on the soil microbial activity and soil aggregation, we ran a soil column experiment in which we applied compost, digestate and lactic acid fermentation product made of the same model bio-waste. The results indicated that OAs produced under anaerobic conditions (fermented product and digestate) increased microbial activity, biomass, and soil micro- and macro-aggregation compared to compost and control treatments. Soil microbial activity strongly correlated to C, Ca, Mg, extracellular polymeric substances (EPS), fungal biomass, and macroaggregate formation (, ). Simultaneously, soil macroaggregate formation strongly correlated to water-extractable C, EPS, cation exchange capacity, K, Mg, Na, and bacterial biomass (, ). This study demonstrated that the effect of an organic substrate on soil properties can be modified towards desired effects using different pre-treatment technologies, suggesting the possibility of “engineer” OAs.