Agricultural use of digestate for horticultural crop production and improvement of soil properties

The usefulness of a digestate from an anaerobic codigestion process as a fertiliser product was evaluated in a field experiment using two horticultural crops (watermelon and cauliflower), during two successive growing seasons. The effects of the digestate were compared with those of a traditional organic amendment (cattle manure) and a conventional mineral fertiliser. Digestate addition to soil provided a source of available nutrients (nitrogen and phosphorus) in the short-term and had positive effects on soil biological properties such as microbial biomass and enzyme activities, compared to the non-amended soil. The digestate application to soil led to yields comparable to the mineral fertilisation for the summer watermelon crop. However, for the winter cauliflower crop, only plots treated with the mineral fertiliser had good production. Nitrogen from the digestate is rapidly and highly available for plant growth in the short-term but also can be easily lost, together with a slow rate of microbial processes due to low temperatures, could reduce the fertilising capacity of the digestate. This seemed to be the main limiting factor for the winter cauliflower crop, where digestate or cattle manure, used as basal dressing, were not enough to satisfy the crop demand for nitrogen during its whole growth cycle.

► Digestate was a source of available nitrogen and phosphorous in the short term.
► Digestate exerted positive effects on soil biological properties.
► Digestate led to good yield results for a summer watermelon crop.
► Organic amendments did not satisfy the nitrogen demand of a winter cauliflower crop.