Kierrätyslannoitteiden vaikutus ohran (Hordeum vulgare L.) fosforin ottoon ja maamurujen kestävyyteen

The use of fertilizers has made it possible to increase agricultural yields, enabling the world’s growing population to be fed. The use of mined phosphorus has created mostly linear phosphorus flow from mines through farms to lakes and oceans. This has clearly deteriorated aquatic ecosystems globally. USA, China and Morocco control over 85 % of global phosphorus reserves and Europe is very dependent on imported phosphorus. To gain phosphorus balance in Europe, it would be important to recycle phosphorus. Recycled fertilizers come from derived currents of agriculture, food industry, forest industry and communities. Only a few studies have been made regarding the effects different recycled fertilizers have on plant’s phosphorus uptake. The aim of this study was to find out how four different recycled fertilizer treatments (ammonium sulphate, liquid digestate, meat bone meal, vinasse) affect barley’s phosphorus uptake and soil aggregate stability, when compared to mineral fertilizer treatment and non-fertilized control treatment. Study material was collected from HYKERRYS 2 -project’s experiment field in growing season 2019. Phosphorus in dry matter was measured and biomass, phosphorus uptake to biomass, fertilizer use efficiency and phosphorus uptake from soil phosphorus reserves were calculated from barley plant samples collected at growth stage 65 (BBCH). Soil aggregate stability analyses, dry sieving and wet sieving, were made to soil samples collected after harvest. Barley’s phosphorus content in dry matter was highest with non-fertilized treatment but other treatments had no differences between them. In biomass quantity or phosphorus uptake on biomass there were no differences between treatments. Fertilizer use was most efficient with ammonium sulphate and least efficient with digestate. Phosphorus uptake from soil phosphorus reserves was least efficient with digestate and mineral fertilizer. The share of soil water stable aggregates had no differences between treatments, but water turbidity was lowest with ammonium sulphate. The results show that recycled fertilizers are fit to replace mineral fertilizers when considering plant’s phosphorus uptake, because there were no notable differences in barley’s phosphorus content, biomass, phosphorus uptake on biomass or soil aggregate stability between different recycled fertilizers and mineral fertilizer. When viewing the results, it should be considered that the soil in experimental field had high phosphorus content and high soil organic matter content to begin with, which made it more difficult to detect the differences than it probably would have been if the soil phosphorus content had been lower. There was also no information available about the forms of the phosphorus in the recycled fertilizers, which made the interpretation of the results difficult, because different forms of phosphorus are differently available for plants. In order to target the use of recycled fertilizers effectively based on crop and soil quality, more knowledge is needed on both the phosphorus forms in recycled fertilizers and recycled fertilizer’s effects on plant’s phosphorus uptake on soils with lower nutrient and organic matter contents.