Physico-chemical and multielemental traits of anaerobic digestate from Mediterranean agro-industrial wastes and assessment as fertiliser for citrus nurseries

Previous researches have demonstrated the bioenergetic potential of agri-food Mediterranean wastes showing that anaerobic co-digestion is a valuable solution for Mediterranean areas. This implies a great interest for anaerobic digestates use in agriculture to replace fertilizers. The present study aimed at: i) producing knowledge on continuous anaerobic co-digestion of feedstock mixture composed by different Mediterranean agri-food wastes in terms of multielemental characterization and ii) assessing the agronomic value of industrial anaerobic digestate (AD) based on the potential as fertiliser in nursery condition for the citrus seedlings. Results have demonstrated that agro-industrial biomasses have great potentiality to be converted by anaerobic digestion in biofertilizer to be used in citrus nurseries as sustainable alternative to mineral fertilisers. Multielemental traits of the tested AD were valuable in terms of nutritional supply for the growth and development of the plant. AD was useful to replace the mineral fertilizers in terms of total N content (10.81 ± 0.32 %TS) and organic matter (43.32 ± 0.80 %TS). The seedlings nutritive status showed that no need for supplemental of nutrients was requested. Volkamer lemon highly benefited from the administration of liquid digestate, increasing the total chlorophyll level (2.97 ± 0.31 mg g⁻¹ FW) presumably due to the higher ammonium content of the AD (59 ± 0.08 %TKN). Besides providing useful tools for citrus nurseries for conceiving new sustainable fertilization strategies, this study is a starting point for further in-depth works on physiological status and traits of citrus plants fertilized by using agro-industrial anaerobic digestate.