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Land degradation reduces productivity and biodiversity, and requires restoration of both soil condition and vegetation to re‐establish ecosystem services. Organic amendments can improve soil biological and chemical properties, thereby enhancing revegetation success in severely degraded soil. This study investigated the use of compost and biochar to support revegetation and soil restoration. Soil was collected from a severely degraded creek bed in an agricultural farm in south‐western Australia (UWA Farm Ridgefield) and amended with compost (2.5% and 5%) and biochar (5% and 10%), both alone and in all pairwise combinations. Saltbush (Atriplex nummularia) seedlings were grown for 10 weeks in glasshouse conditions. Following harvest, plant growth and soil chemical properties were analysed. DNA was extracted from rhizosphere soil for bacterial diversity profiling with subsequent putative functional genes relating to carbon, nitrogen and phosphorus cycling using an in‐silico approach. Compost improved growth of root and shoot biomass. Both compost and biochar improved the alkaline soil by reducing pH and increasing nitrate, phosphorus and potassium levels. Compost addition also had a significant effect on rhizosphere bacterial community structure, decreasing alpha diversity and altering beta diversity indices. Amendment of soil also changed the relative abundance of putative nutrient cycling genes, with an increase in the potential for denitrification, carbon and phosphorus cycling and a decrease in ammonification potential. Application of this compost‐biochar combination improved plant growth and soil condition by altering both chemical and biological characteristics of the soil, and therefore may provide an effective management strategy for supporting restoration in a degraded landscape. [ABSTRACT FROM AUTHOR]

The influence of biochar (biomass-derived black carbon) on crop growth and nutrient uptake varies based on the rate of biochar applied with fertilisers. We investigated the effect of deep-banded oil mallee biochar at different rates (0, 1.5, 3.0, and 6 t/ha) with 2 types of fertiliser (non-inoculated MultiMAPS® at 30 or 55 kg/ha; inoculated Western Mineral Fertiliser at 100 kg/ha) on wheat growth at a farmer's field in a low rainfall area of Western Australia. Wheat yield increased significantly when biochar was applied with inoculated fertiliser and 30 kg/ha non-inoculated fertiliser. Mycorrhizal colonisation in wheat roots increased significantly with biochar application with inoculated mineral fertiliser. Mycorrhizal hyphae may have improved water supply to reduce drought stress in these treatments by extending crop exploration of water from the wide inter-rows. Grain yield increases were due to better grain survival and grain fill with reduced drought stress. Early stage phosphorus uptake was not improved by mycorrhizal colonisation- phosphorus supply from the soil and applied fertiliser was already adequate. The residual effect of biochar and mineral fertilisers was assessed using a mycorrhizal bioassay for soil collected from the field trial 2 years after application of biochar. Biochar and both fertilisers increased mycorrhizal colonisation in clover bioassay plants. Deep-banded biochar provided suitable conditions for mycorrhizal fungi to colonise plant roots. Additional keywords: biochar, mineral fertilisers, mycorrhizal fungi, soluble fertilisers, wheat., Introduction Oil mallee (Eucalyptus oleosa) is the first native woody perennial species promoted as a commercial crop in the lower rainfall areas of the south-west land division of Western Australia [...]