The effects of drought on soil and microbial nutrients and their relationship with plant growth in pasture systems

Abstract

Climate change characterised by increasing drought periods and warming is projected to negatively affect future pasture production, especially in Australia. In the absence of adaptation, these drought and warming events will alter the biogeochemical cycling of carbon (C), nitrogen (N) and phosphorus (P) essential for microbial functioning and plant growth. Soil nutrient limitations imposed by drought could negatively affect the ability of microbes to cycle nutrients, further limiting plant nutrient accessibility with potentially negative consequences for the productivity of pasture systems. Therefore, the understanding of soil and microbial nutrient responses to drought is crucial to developing adaptation/management strategies that could help pasture systems adapt to future climates.

Overall, this study identified some novelty associated with a) soil nutrient and microbial responses to drought across a suite of plant species used for pasture production in Australia, b) soil nutrient response to water stress in degraded systems analogous to an intensively managed system with microbial inoculum, and a system with differing soil type also analogous to the heterogeneous nature of Australian pasture systems. This study also provides insight into microbial and soil nutrient responses to climate change under pasture systems and their linkages with plant growth. Drought decreased nutrient availability and microbial biomass with an effect persisting post-drought for most plant species (chapter 2). There is potential to improve soil nutrient availability in a water-stressed system with arbuscular mycorrhizal fungi, especially in non-degraded systems (chapter 3). In addition, soil nutrients and microbial biomass can also be improved in droughted systems using plant bio-stimulant at lower fertiliser rates in light textured soil, and at higher fertiliser rates in heavier textured soil (chapter 4). The application of this knowledge will help farmers adapt their nutrient management systems to future climates, especially in intensively managed systems spanning different plant species and soil types.

Date of Thesis submission	2022
Original language	English
Awarding Institution	Western Sydney University
Supervisor	Catriona Macdonald (Supervisor) & Yolima Carrillo Espanol (Supervisor)