Impact of irrigation and fertilization on soil potassium, pH, as well as yield and quality of Panax Notoginseng

【Objective】 Panax Notoginseng is a medicinal herb and primarily grown in Southern China. This paper investigates the impact of irrigation and fertilization on soil potassium and pH, as well as yield and quality of Panax Notoginseng. 【Method】 The experiment was conducted in Dalishu Village, Luxi County, located in the Honghe Hani and Yi Autonomous Prefecture, Yunnan Province. It consisted of four fertilizations by applying the 480 kg/hm2 of fertilizers at different ratios in the seedling, flowering, fruiting and root gain stages: 25%∶25%∶25%∶25%(F1), 25%∶30%∶20%∶25%(F2), 30%∶30%∶15%∶25%(F3), and 40%∶20%∶10%∶30%(F4). Each fertilization had three irrigation treatments: 200 m3/hm2(W1), 300 m3/hm2(W2) and 400 m3/hm2(W3). The control (CK) was F1 combined with 92 m3/hm2 of irrigation. In each treatment, we measured the changes in soil potassium content and pH. The technique for order preference by similarity to ideal solution (TOPSIS) was used to evaluate all treatments. 【Result】 ① When irrigation and fertilization were the same, soil pH decreased with soil depth and tended to stabilize as the crop grew. The soil pH showed little sensitive to fertilization. When irrigation was the same, the average soil pH was lower in the four treatments than in the CK. During the experimental period, pH of the 0-60 cm soil in different treatments varied from 4.80-8.66. W3F1, W2F4 and W2F3 gave the optimal soil pH for the crop to grow. ② Both total and available soil potassium decreased with increasing soil depth. As the crop grew, the total potassium in the 0-60 cm soil layer increased, while the available potassium decreased initially before increasing. With increasing irrigation amount, total soil potassium decreased, while the available potassium increased initially followed by a decline. Fertilization influenced the dynamics of total and available potassium. Irrespective of fertilization and irrigation, potassium uptake by roots in different growing stages was ranked as follows: fruiting period>flowering period>root weight gain period>seedling stage. Of all the treatments, W2F3 was optimal for soil potassium, with total and available potassium being 10.40 g/kg and 56.69 mg/kg, respectively. ③ Regardless of fertilization, with the increase in irrigation amount, the yield and partial factor productivity (PFP) of the crop increased first followed by a decline. The yield, water use efficiency and PFP varied with fertilization. TOPSIS analysis showed that the optimal irrigation was 300 m3/hm2 and the optimal fertilization was applying 144, 144, 72 kg/hm2 and 120 kg/hm2 of fertilizers in the seedling, flowering, fruiting and root weight gain stage, respectively. 【Conclusion】 Based on soil potassium, pH, as well as yield and quality of Panax Notoginseng, the optimal irrigation and fertilization for Panax Notoginseng production in the studied area were irrigating 300 m3/hm2 and applying 144, 144, 72 kg/hm2 and 120 kg/hm2 of fertilizers in the seedling, flowering, fruiting and root weight gain stage, respectively.