Biosolids blended with edaphic supports mimic structural and biochemical features of natural soils and foster plant biomass growth

Abstract

Biosolids can be blended with edaphic components to formulate customized soil mixes (Technosols), where specific nutrient levels, moisture content, and other factors are tailored to support plant growth. The aim of this work was to evaluate constructed Technosols regarding specific physical, rheological, and biochemical characteristics, as well as for their ability to meet the growth requirements of rye grass. Soil horizons A and C, and quarry waste, were examined both individually as controls and in binary combinations with biosolids, maintaining a ratio of 70:30 in a replicated pot experiment. After 35 days, half of the pots were seeded with ryegrass (Lolium perenne ssp). After 3,5 months, the following physical, chemical, and rheological properties were measured: bulk density; plastic limit; liquid limit; saturated hydraulic conductivity; aggregate stability, organic matter and total Kjeldahl nitrogen. Enzyme activities were determined using fluorogenic substrates, whereas total bacterial and fungal composition was assessed through qPCR and amplicon sequencing using respectively 16S rRNA gene and ITS gene primers. Biosolids-based Technosols exhibited soil-like behavior across various examined variables, such as aggregate stability, microbial community composition and the yield of harvested plant biomass. Changes in the physical and chemical characteristics of mixtures containing biosolids were accompanied by corresponding changes in enzyme activities, as well as by shifts in absolute bacterial and fungal abundance. Biosolid-based Technosols possess the capability to establish sustainable and effective aggregation conditions, maintaining satisfactory water retention levels, and fostering favorable microbiological and biochemical conditions to fulfill essential soil functions, including biomass production.