Barley can utilise algal fertiliser to maintain yield and selected malt quality indicators compared to mineral fertiliser

Abstract Background and aims Mineral fertilisers are essential for global crop productivity. However, their use is unsustainable due to high energy costs from sourcing and processing, and nitrous oxide emissions after application. An alternative proposition is the use of microalgal biomass as a nutrient source for fertilisation. To date, there is limited data on how the productivity of barley grown with microalgae would compare to barley grown with mineral fertilisers. Furthermore, the impact of the fertiliser source on suitability of grain for malting, one of barley’s main end uses, should be considered. Methods We quantified the phenology, reflectance indices and yield components of barley cv. Laureate grown with either Chlorella vulgaris powder or mineral fertiliser in three glasshouse trials in different soils, to assess the robustness of our findings under soil-to-soil variation. We extended this to carry out a field trial from which we malted the grain collected at the end of the season and quantified malt quality. Results We hypothesised that there would be no statistically significant difference in plant performance when grown with microalgae or mineral fertiliser when nitrogen addition was equal. All glasshouse trials and a field trial showed that plants grown with microalgae and mineral fertiliser do not significantly differ in any yield component, yield itself, or measure of malt quality except total malt nitrogen. Conclusions Supplying the same amount of nitrogen to plants via microalgal biomass instead of mineral fertiliser produced barley with not significantly different yield and selected malt quality indicators as plants grown with mineral fertiliser.