The Changes of Several Endogenous Phytohormones during Microtuber Formation in vitro in Solanum tuberosum L. The Changes of Several Endogenous Phytohormones during Microtuber Formation in vitro in Solanum tuberosum L. Soil fumigation and bio-organic fertilizer application promotes potato growth and affects soil bio-chemical properties in a continuous cropping system A study on the use of fulvic acid to improve growth and resistance in continuous cropping of potato