Effect Of Oxygenated Subsurface Drip Irrigation Coupled With Fertilization Amount On The Soil Microenvironment And Growth Of Panax Notoginseng

The yield of Panax notoginseng（Bur K.）F.H.Chen in Yunnan Province accounted for more than 90%of China’s total yield,but traditional growers seek high yields per unit,and extensive water and fertilizer management leads to a waste of water and fertilizer resources and frequent disease,which in turn leads to lower yields and poorer quality.Therefore,this experimental study attempted to propose a scientific and reasonable irrigation and fertilizer management strategy for Panax notoginseng green production.A one-year experimental study was conducted at the Smart Agriculture Teaching and Research Base of Kunming University of Technology to investigate the effects of different fertilizer applications combined with different irrigation conditions on soil moisture and nutrient distribution,soil enzyme activity,soil microbial community structure,physiological growth characteristics,root rot,yield,quality,and water-fertilizer use efficiency of Panax notoginseng.The 5-year-old Panax notoginseng was used as the study subject,three types of irrigation were set up,oxygenated subsurface drip irrigation（OI）,micro-sprinkler irrigation（SI）,and surface drip irrigation（DI）,respectively,and four organic fertilizer application rates,low fertilizer F₁:75 kg·ha^-1,medium fertilizer F₂:100kg·ha^-1,medium-high fertilizer F₃:125 kg·ha^-1,and high fertilizer F₄:150 kg·ha^-1,respectively.A complete combination design was used with a total of 12 treatments and 3 replications per treatment,for a total of 36 experimental plots.The results of this study showed that.（1）Oxygenated subsurface drip irrigation（OI）significantly increased the soil water and nutrient content in the 0-40 cm soil layer in the root zone of Panax notoginseng.Under the OI treatment,with the increasing organic fertilizer application,soil moisture increased then decreased and nutrient content increased,and led to reduced partial fertilizer productivity（PFP）.In addition,with the reproductive period of Panax notoginseng progressed,the magnitude of soil water content in the root zone of Panax notoginseng at different stages mainly showed seedling stage>flowering stage>root growth stage>fruiting stage,while the nutrients content gradually decreased,showed seedling stage>flowering stage>fruiting stage>root growth stage.（2）OIF₃ treatment increased soil catalase,urease,and phosphatase activities,and showed a trend of increased and then decreased with the growth stage of Panax notoginseng progressed,showed flowering stage>fruiting stage>seedling stage>root growth stage.The OIF₃ treatment also significantly increased the number of soil bacteria and actinomycetes colonies,and decreased the number of fungi colonies.With the reproductive period of Panax notoginseng progressed,the number of microbial communities in Panax notoginseng showed flowering stage>fruiting stage>root growth stage>seedling stage.（3）SIF₃ treatment significantly increased the growth of Panax notoginseng plant height,stem thickness,leaf length,leaf width,and leaf area.With the reproductive period of Panax notoginseng progressed,obtained the highest net photosynthetic rate(4.29μmol·m^-2·s^-1),stomatal conductivity(0.046 mmol·m^-2·s^-1),and transpiration rate(1.73 mmol·m^-2·s^-1).The SIF₃treatment also promoted canopy and shoot hydraulic conductivity.The OIF₃ treatment significantly promoted Panax notoginseng root growth,root hydraulic conductivity,and root-shoot ratio.（4）OIF₃ treatment obtained the lowest incidence of root rot（5.72%）,the highest yield(4649.70 kg·ha^-1),irrigation water use efficiency(9.69 kg·m^-3),partial fertilizer productivity(1.55 kg·kg^-1),and total saponin content（12.50%）.Based on the above results,the TOPSIS model was used to comprehensively evaluate the yield,irrigation water use efficiency,partial fertilizer productivity,and total saponin content of Panax notoginseng.We found that the synergistic effect of oxygenated subsurface drip irrigation（OI）combined with fertilizer application of 125 kg·ha^-1（F₃）could reduce the root rot of Panax notoginseng and improve root growth,water-fertilizer productivity,and quality.