Soil amendment with biochar: growth, physiology and fruit yield and quality of young 'Fuji' trees

Declining soil health in perennial fruit tree orchards is a concern due to long term lack of carbon inputs. The objective of this study was to investigate the effects of different soil amendments on the growth, physiology and fruit yield and quality of ‘Fuji’ apple trees on M.26 rootstock in a ‘replant’ soil. Treatments included application of a low-temperature-derived green-waste biochar at 47 t ha^-1, compost application at 10 t ha^-1, biochar plus compost application, and control. Trunk girth of trees in the biochar plus compost treatment was significantly greater than that of the control while the biochar or compost only treatments were intermediate. Leaf pre-dawn and midday water potentials were not significantly different between treatments as measured during the second cropping season. Lack of a significant difference in tree water- and nutrient-relations between treatments was attributed to the site receiving excess nutrients and irrigation such that potential effects of biochar and compost on increased water and nutrient availability were not realized. The increased trunk girth of trees in the biochar plus compost treatment was attributed in part to synergistic effect of biochar plus compost on soil microbial community in the context of this replant situation. Other effects of soil amendment with biochar may become evident on this site in dry seasons.