Effect of rock dust-amended compost on the soil properties, soil microbial activity, and fruit production in an apple orchard from the Jiangsu province of China

This study examined the effect of compost fortified with rock dust on the soil properties, soil microbial activity, and yield and fruit quality in a mature apple orchard from the Jiangsu province of China. The incor-poration of rock dust significantly improved the microelement contents of Ca, Mg, Fe, Mn, Zn, B, and Al, but without increasing phytotoxicity of the compost. The fortified compost had higher metabolic activity and functional diversity of microorganisms as determined by the community-level physiological profiling with Biolog EcoPlates. The two-year incorporation of the rock dust compost into a poor-quality soil led to a significant increase in the yield with the increase of 120% and 187% compared to untreated control in 2013 and 2014, respectively. Application of rock dust compost obviously promoted superoxide dismutase (SOD) activity and concentration of vitamin C in mature apple trees. The beneficial effects coincided with higher microbial activity and shifts in the composition of the soil microbiome. Our results demonstrate that the practice of combining the rock dust-fortified compost with NPK fertilizers provides a cost- effective way of supplying crops with macro-and micronutrients ensuring better vegetative growth and higher yields.