For biochemical modification of the root-soil interface, the engineered secretion of stable enzymes from trichoblasts (= root hair bearing rhizodermal cells) is proposed. As a reporter activity, we chose to express a synthetic gene encoding a secretory phytase (PHY) directed by a trichoblast-specific promoter in root hair cells of the crop plant potato. Transgenic plants produced and secreted phytase in sufficient amounts to release phosphate from phytate in liquid medium. When grown in an unsterile substrate containing phytate, transgenic plants accumulated 40% more P in leaves than wild-type plants. The improved P nutrition driven by trichoblast-targeted expression and subsequent secretion of PHY illustrates the potential of using trichoblast-targeted expression of suitable enzymes for future applications in plant nutrition, phytoremediation and molecular farming.