Influence of Aged Wood Biochar on Mycorrhizal Colonisation, Growth and Leaf Gas Exchange of Wheat and Clover with Different Water Regimes

Water scarcity is one of the most limiting environmental factors for crop productivity globally, where biochar application can play a role. To test this, a glasshouse experiment was conducted with aged biochar application with water regimes on arbuscular mycorrhizal fungi colonisation, plant growth, phosphorus nutrition and leaf gas exchange in wheat and subterranean clover. Six treatment combinations (two biochar levels of 0 and 6 t ha−1; and three water regimes of well-watered, water-stressed and watering intermittently) were arranged in factorial completely randomized block design with three replications. The wheat and subterranean clover were grown and harvested 14, 24, 34 and 44 days after sowing. In this study, aged biochar had no significant effect on plant growth for both wheat and clover, regardless of water regimes. Shoot and root dry weights increased in well-watered conditions compared to water-stressed conditions. Root length and colonised root length increased with biochar addition for wheat, mostly in well-watered treatment. Phosphorus uptake increased in biochar treatment, and the effect was higher in well-watered conditions. Leaf photosynthetic rate (PN), stomatal conductance (gs), intercellular CO2 concentration (Ci) and transpiration rate (E) increased with biochar addition. For clover, the effect was higher in water-stressed than well-watered conditions. These results suggest that biochar may enhance water availability to clover plants in water-stressed conditions. However, the positive effect of biochar on plant growth under water-stressed conditions, varied with plant species, needs to be explored further in a range of crop species and biochar sources in addition to the material used in the current investigation.