Presentation SOILCOM in Ramiran 2023
Compost application to land has beneficial impacts on soil characteristics, e.g. for nutrient status, pH, increasing soil carbon content, and soil life (Diacono and Montemurro, 2010; D'Hose et al., 2016). However, compost characteristics, and the effects when incorporated into soil, can differ widely due to the large variety of feedstocks and composting practice (Raviv, 2005). Information on compost characteristics is crucial in the promotion of compost use by farmers who, sometimes, are reluctant due to bad experiences with ill-defined, contaminated, or impure compost. During the North Sea Region Interreg project Soilcom (2019-2023) 62 composts from varying origin were collected and analysed for physical, chemical and biological parameters (Amery et al., 2020) in order to show averages, ranges and relationships in compost characteristics and links with feedstocks and composting practices.
Methodology
Thirty-eight composts from commercial producers and 29 farm composts were collected during 2019-2022 from Flanders (Belgium), The Netherlands, Germany, Denmark and Scotland. Chemical (moisture, pH, electrical conductivity (EC), NO3- and NH4+ in water extract, organic matter (OM), volume weight, cell wall components, total (TC), inorganic (IC) and organic carbon (TOC), Total Nitrogen (TN), total macro elements and heavy metals, cation exchange capacity (CEC), germinating weeds and impurities) and biological parameters (phospholipid fatty acid (PLFA) determination to distinguish bacterial and fungal groups) were measured at ILVO Unit Plant Laboratory Crop and Husbandry (Belgium), physical parameters (particle size distribution, bulk density, hydraulic conductivity and water holding capacity) were assessed by the James Hutton Institute.
Results and discussion
A preliminary data analysis on a refined selection of the data set revealed 5- to 10-fold variation in most of the compost characteristics highlighting significant variability based on origin, feedstock, and composting practice. Farm composts had in general higher OM, TN, CEC, and total biomass compared to composts from commercial producers. Compost CEC and total biomass were partly explained by the OM content of the compost. It should be noted that all composts had heavy metal contents and impurities below legal thresholds. A final and more detailed analysis on all composts, including results of physical analysis, including bacterial and fungal groups, will be completed and presented at the RAMIRAN conference.