Mulching effects on the quality formation of medicinal materials and rhizosphere soil microenvironment in Notopterygium franchetii in the Qinghai-Tibet Plateau

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ABSTRACT Different cultivation methods directly affect the quality of medicinal materials, to gain insights into the effects of different type of mulching on the quality of Notopterygium franchetii root medicinal materials, farmland experiments were conducted in the Qinghai-Tibet Plateau. We subjected two-year-old Notopterygium franchetii seedling to five mulching treatments: no mulching (CK, control), coarse sand mulching (CM), grassy mulching (GM), stalk mulching (SM), and plastic mulching (PM). Following these treatments, we determined the moisture content, pH, NPK contents, and enzymeatic activity of the soil, and morphological indexes and content of the main components of root. Stalk mulching and PM increased the main root biomass by increasing its ground diameter and reduced branched root biomass by reducing the number of branched roots produced. Grassy mulching increased the root biomass by promoting main root elongation. Mulching increased the total content of the six main root components, with the most significant change obtained with GM, but the pattern of change of the different components varied among the mulch treatments. Contents of NPK were significantly higher than in the control with GM, but decreased with PM. Coarse sand mulching and PM significantly reduced the activities of urease and sucrase, and SM significantly increased the activities of urease, catalase and sucrase, but significantly decreased that of phosphatase. Furthermore, GM significantly increased phosphatase and sucrase activities, while CM significantly decreased urease and sucrase activities. Various soil enzymes and its pH promote main root bioaccumulation by increasing the root ground diameter or main root length. Sucrase activity promoted the accumulation of ferulic acid, psoralen, and notopterol content, and inhibited the accumulation of chlorogenic acid and nodakenin. Elevated soil water content promoted the accumulation of ferulic acid, notopterol and nodakenin, and inhibited isoimperatorin accumulation. Hence, NPK, pH, and various enzymes have different effects on the accumulation of major components in the root. The effect of mulching is closely linked to root growth and distribution, as well as to the soil environment. Various soil factors affect the quality of medicinal materials differently and, ultimately, can work together to form an equilibrium state that benefit the accumulation of main root biomass and main components with medicinal interest in Notopterygium franchetii.