Irrigation combined with organic fertilizer could promote the environmental health of soil available nutrients and improve the functional activity of saponins in Panax Notoginseng

Farmers increased the amount of irrigation, excessive application of pesticides and fertilizers to improve the economic income of Panax Notoginseng, resulting in several negative consequences, including the degradation of soil structure, the disruption of nutrient cycling, decreased resource use efficiency, and a decline in the functional activity of saponins. Field experiment was conducted in the experimental base of Panax Notoginseng Research Institute, Luxi County, Honghe Prefecture, Yunnan Province from 2018 to 2021. The split ratio of organic fertilizer application were proportioned according to the reproductive stages of Panax Notoginseng (rooting: seedling: flowering: fruiting), F1 (15:15:15:15), F2 (12:15:18:15), F3 (9:18:18:15), F4 (6:24:12:18 kg·ha⁻¹), the amount of organic fertilizer applied every year is 1440 kg·ha⁻¹, set three irrigation quota levels W1(5 mm), W2 (10 mm) and W3 (15 mm).A water-fertilizer coupling experiment was conducted with four fertilization levels and three irrigation quota levels, resulting in a total of 12 experimental plots. The planting experience of local farmers was irrigation of 20 mm and fertilizer of 120 kg∙ha⁻¹ per time, total irrigation of 480 mm and total fertilizer of 2880 kg∙ha⁻¹ per year as control treatment (CK), the irrigation and fertilization frequency were twice a month. The study investigated the response patterns of soil pH, SW, SOM, TN, AP, and AK to different irrigation levels combined with organic fertilizer ratios during the rooting, seedling, flowering, and fruiting stages of Panax notoginseng over four consecutive years. It also assessed their role in promoting the environmental health of soil nutrient availability. The research aimed to clarify the functional activities of notoginsenosides R₁, Rg₁, Re, Rb₁, Rd, explore their correlations, identify key influencing factors, and propose the optimal irrigation and organic fertilizer combination scheme. The results showed that the soil nutrient environmental quality, physiological growth and saponin functional activity of Panax Notoginseng were significantly correlated with irrigation water combined with organic fertilizer at different growth stages (P < 0.05). The maximum of pH, SW, SOM, TN, AP, AK content appeared in the 2020. These values increased by 21.31, 6.31, 31.83, 21.83, 22.35, 33.06 %, in the 2020 compared to the 2018. The application of organic fertilizer increased the yield by 23.1–30.8 %, increased the leaf area index by 21.4–29.6 %, increased the functional activity by 18.6–24.4 %.With increase of irrigation amount, R₁, Rg₁, Re, Rd increased at root stage, seedling stage and flowering stage, decreased at fruit stage, Rb₁ first decreased and then increased, R₁, Rg₁, Re, Rb₁, Rd increased year by year for four consecutive years SW has a greater effect on partial factor productivity of fertilizer and saponin content. pH, SW, SOM, TN, AP and AK, LAI, PFP, WP, Y of with irrigation and organic fertilizer combinations, R₁, Rg₁, Re, Rb₁, Rd of had significant clustering phenomenon. After a comprehensive evaluation used by VIKOR method, Q_i is the benefit ratio. The W2F3 had the smallest Q_i with a value of 0.04 as well as ranked first. the second was W2F4 with a Q_i of 0.06. The CK had the largest Q_i with a value of 1.00 and was ranked thirteenth. Based on the above results, the optimal irrigation combined with organic fertilizer can be derived as W2F3, as well as its LAI of 1.65, Y of 2663.96 kg∙ha⁻¹, PFP of ¹.07 kg·kg⁻¹, WP of 1^.53 kg·m⁻³. This study provided a theoretical basis for improving soil micro-ecological environment for a healthy and efficient top-quality yield of Panax Notoginsen.