Sustainable soil management in agriculture under drought stress: Utilising waste-derived organic soil amendments and beneficial impacts on soil bacterial processes

Drought can negatively impact agricultural productivity, not only by reducing water availability for plant growth, but also by disrupting soil microorganisms involved in nutrient cycling and soil functionality. Addressing these impacts necessitates a systems-based approach, which can involve integrating waste-derived organic soil amendments like compost, digestate, frass, biochar, and biosolids. Compost, digestate, frass and biosolids enhance microbial activity and diversity by providing available nutrients and carbon to sustain bacterial growth. Biochar can contribute to soil structure improvement and water retention, aiding bacteria survival during drought. Given the higher susceptibility of bacteria to drought than fungi, this review focuses on soil bacterial community responses, activity, diversity, and nutrient cycling to drought stress and the influence of waste-derived organic soil amendments on bacterial strategies and function. Under drought stress, waste-derived organic soil amendments can directly enhance soil bacterial community resilience, offering a conducive habitat, food source, and essential nutrients. The beneficial compounds in these products also indirectly enhance the ability of bacteria to withstand adverse conditions. The preference for bacterial K-strategists during drought, facilitated by organic inputs, promotes efficient nutrient cycling. Furthermore, post-application diversity indices demonstrate that soil organic amendments stabilise the bacterial community, improving soil health and plant growth during drought stress. Future studies should focus on long-term evaluations of waste-derived organic soil amendments on soil bacterial diversity and function at the field scale, encompassing various ecosystems and soil types under drought stress. Ultimately, organic soil amendments derived from waste management processes offer dual benefits of ensuring soil health and contributing to circular economy goals.