Application of Phytogenic Liquid Supplementation in Soil Microbiome Restoration in Queensland Pasture Dieback

Pasture production is vital in cattle farming as it provides animals with food and nutrients. Australia, as a significant global beef producer, has been experiencing pasture dieback, a syndrome of deteriorating grassland that results in the loss of grass and the expansion of weeds. Despite two decades of research and many remediation attempts, there has yet to be a breakthrough in understanding the causes or mechanisms involved. Suggested causes of this phenomenon include soil and plant microbial pathogens, insect infestation, extreme heat stress, radiation, and others. Plants produce a range of phytomolecules with antifungal, antibacterial, antiviral, growth-promoting, and immunostimulant effects to protect themselves from a range of environmental stresses. These products are currently used more in human and veterinary health than in agronomy. In this study, we applied a phytogenic product containing citric acid, carvacrol, and cinnamaldehyde, to investigate its ability to alleviate pasture dieback. The phytogenic liquid-based solution was sprayed twice, one week apart, at 5.4 L per hectare. The soil microbial community was investigated longitudinally to determine long-term effects, and pasture productivity and plant morphometric improvements were explored. The phytogenic liquid significantly improved post-drought recovery of alpha diversity and altered temporal and spatial change in the community. The phytogenic liquid reduced biomarker genera associated with poor and polluted soils and significantly promoted plant and soil beneficial bacteria associated with plant rhizosphere and a range of soil benefits. Phytogenic liquid application produced plant morphology improvements and a consistent enhancement of pasture productivity extending beyond 18 months post-application. Our data show that phytogenic products used in the livestock market as an alternative to antibiotics may also have a beneficial role in agriculture, especially in the light of climate change-related soil maintenance and remediation.