Barley Can Utilise Algal Feriliser to Maintain Yield and Malt Quality Compared to Mineral Fertiliser

Use of fertiliser is essential for global crop productivity; however, their use is unsustainable through high energy costs from sourcing, nitrous oxide emissions during application, and the potential to cause eutrophication if used in excess. An alternative proposition is use of microalgal biomass for fertilisation, which adds carbon to the soil, is as effective as mineral fertiliser when comparing the vegetative grown of wheat and barley, and has the advantage of accumulating nutrients present in wastewater if used as a growth media, with 80-90% removal efficiencies for N and P. This means algae can both be used as a fertiliser and wastewater treatment, which supports the possibility of recycling nutrients within the barley to malt to whisky value chain, as nutrients from pot ale and spent lees could be reclaimed and used on the subsequent barley crop. This study is the first step in realising that circular economy. We sought to quantify the phenology, reflectance indices, yield components (including yield itself) and malt quality of barley cv. Laureate grown with either Chlorella vulgaris powder or mineral fertiliser, with both treatments providing equal amounts of nitrogen at the appropriate level for malting spring barley, 118kg(N)/ha accounting for soil mineral nitrogen. We performed three glasshouse experiments to assess the repeatability of our findings and performed a field trial from which we malted the grain. Both lines of inquiry showed that plants grown with algae and mineral fertiliser do not significantly differ in any yield component, yield or malt quality, with the exception of total malt nitrogen. This study is an important proof of concept for enabling further, larger algal fertiliser trials, such as increasing the number of field sites under different environmental conditions to assess the widespread viability.