Nutrient release from alternative fertilisers from nutrient-rich wastes under field conditions

Abstract The production of organic wastes is increasing worldwide, while there is a great need for new organic nutrient sources in organic agriculture systems. Therefore, the recycling of these organic wastes as fertilisers could help to improve soil fertility while maintaining or increasing the organic food production. In this study, we investigated the ability of manure, digested manure, manure co-digested with the organic fraction of municipal solid waste, Fertigro®, and ash from straw applied singly or combined for better N:P:K:S ratios to supply available nutrients for spring barley in a one-year field trial. The fertilisation of spring barley with Fertigro® applied individually increased plant biomass, the total content of N, S, and Na and micronutrient levels (Al, Cu, Fe and Zn) in plants, reaching similar values to their respective positive controls. In addition, Fertigro® increased electrical conductivity in soil compared to unfertilised soil but the values were similar to all the other amendments, however, no evidence of salinity stress for plant growth was observed. Manure and digested manures showed similar plant growth, however, anaerobic digestion reduced the apparent N recovery compared to the raw manure. Finally, the combination of digested manure with Fertigro® and ash tended to increase plant growth and nutrient uptake compared to the single application of digested manure, suggesting that the combination of these organic wastes can supply sufficient amounts of N, P, K and S for spring barley to grow without detrimental effects, highlighting their potential value as alternative bio-based fertilisers in organic systems.