Abstract/Summary

Sustainable development goals and net-zero target policies necessitate the progression of livestock production from ryegrass monocultures to grassland diversity. Regenerative agricultural farming techniques could meet nitrogen requirements for grassland systems and enhance their resilience to climate change. Little is known, however, about how plant diversity in farming systems affects the soil and its biota in the short term. This work addresses the knowledge gap by researching the impact of commercially viable diverse forage mixtures on soils and soil biota, all measured within one system. A conventionally fertilised ryegrass monoculture was compared to three unfertilised diverse grasslands differing in plant diversity. Multiple key differences in soil biota were observed as a result of enhancing plant diversity: higher earthworm densities, higher arbuscular mycorrhizal fungi (AMF) root colonisation and higher fungal diversity. A model predicting aboveground biomass production showed that AMF colonisation was the only factor explaining the increase in aboveground biomass at low soil water availability. Additionally, AMF community composition was similar under all diverse mixtures suggesting benefits achieved by AMF presence are equal under a 6 and 17-species grassland. Plant mixtures positively affecting soil microbial community due to their diversity and interspecific competition, especially in environments where future droughts are more likely, will be better at maintaining their productivity as a result of AMF symbiosis increasing the root surface area. Further, the diverse forages investigated in this research reduce the need for external inputs, an outcome with clear and positive implications for farm profitability and environmental impact whilst improving soil health by enhancing abundance and diversity of ecosystem engineers.