Study On The Effect Of Water And Fertilizer Regulation On The Diversity Of Soil Bacteria And Their Enzymatic Activity In Micro-Sprinkler Irrigated Panax Notoginseng

Excessive application of water and fertilizer during Panax pseudoginseng cultivation can easily lead to waste of water and fertilizer,high incidence of Panax pseudoginseng diseases,low yield,and poor quality.To study the interrelationship between different water and fertilizer regulating treatments on the structural diversity of soil bacterial communities,physicochemical properties,and soil enzymes,and to select the best water and fertilizer application method.It is of great practical importance to provide the scientific basis for improving the yield and quality of Panax notoginseng.In this paper,Panax ginseng farmland in Luxi County,Yunnan Province was used for the study,and the experiment was conducted from 2018 to2021 at a typical Panax ginseng planting base in Daliushu Village,Luxi County.The trial was set up with four fertilizer levels(F1,F2,F3,and F4),three irrigation levels(W1,W2,and W3),and one CK treatment,for a total of 13 experimental treatments.The interrelationships between the structural diversity of soil bacterial communities,physicochemical properties,and soil enzymes under different water and fertilizer regulation treatments were analyzed,and a comprehensive ranking was conducted using the quotient TOPSIS analysis,to select the best water and fertilizer application method to achieve the optimal combination of water and fertilizer and provide a scientific basis for improving the soil fertility of Panax notoginseng.The main findings were as follows:(1)Soil enzyme activity at different growth periods tended to increase and then decrease as the growth periods extend of Panax notoginseng increased.From largest to smallest in order of flowering period,fruiting period,seedling period,and rooting period.The soil enzyme activity of different water and fertilizer regulation treatments was the largest in W3F4 treatment.Soil enzyme activity decreased as the soil layer deepened,with the greatest vertical difference of 73.18%between the 0-20cm and40-60cm soil layers in the W1F1 treatment for acid phosphatase at the seedling stage.Variations in temperature,rainfall,and evaporation during the different growth periods of Panax ginseng resulted in greater enzyme activity in Panax ginseng soils during the flowering and fruiting periods(rainy season)than during the root growth and seedling periods(dry season).Changes in litter accumulation,microbial activity,and the amount of irrigation and fertilization resulted in significant differences in the vertical distribution of Panax notoginseng enzyme activity between different soil layers.(2)The main dominant phyla of bacteria in the different water and fertilizer control treatments were Amoebacteria,Acidobacteria,and Actinobacteria,the main dominant class wereγ-Amoebacteria class,α-Amoebacteria class,Actinobacteria class,the main dominant genera were Vicinamibacteraceae＿norank,Subgroup6＿norank,Vicinamibacterales＿norank,and Bacillus.The soil bacterial community at the phylum,class,and genus levels tended to decrease and then increase with a prolonged growth period,with the largest in the fruiting period and the smallest in the seedling period.W1F2,W2F3 and W3F4 treatments helped to increase the abundance of soil bacterial communities at the phylum,class,and genus levels in Panax notoginseng.(3)Total nitrogen,nitrate nitrogen,ammonium nitrogen,total phosphorus,effective phosphorus,total potassium,and organic matter of Panax ginseng soils at different growth periods showed a trend of increasing and then decreasing with the prolonged growth period,from largest to smallest being the flowering period>fruiting period>seedling period>rooting period.Of the 13 water and fertilizer control treatments W3F4,W3F3 and W2F4 treatments had a greater effect on the physicochemical properties.(4)Soil ammonium nitrogen was significantly negatively correlated(P<0.05)with bacterial diversity in different water and fertilizer regimen treatments and was an important factor affecting bacterial diversity.Total soil N,total phosphorus,total potassium,effective phosphorus,and organic matter showed highly significant positive correlations with urease,sucrase,acid phosphatase,and catalase(P<0.01).Total nitrogen,total phosphorus,total potassium,effective phosphorus,effective potassium,and organic matter were the key factors affecting enzyme activity.Soil ammonium nitrogen,nitrate nitrogen,and p H were important factors affecting enzyme activity.(5)Entropy-weighted TOPSIS analysis of soil enzyme activity,bacterial diversity,bacterial community structure,and physicochemical properties showed that the comprehensive ranking result of W2F4 treatment ranked 1st in terms of relative proximity C value,indicating that W2F4 is the optimal water and fertilizer treatment,it is beneficial to improve the soil fertility of Panax notoginseng.In conclusion,the optimal irrigation and fertilization system for Panax pseudoginseng under different water and fertilizer control was the W2F4 treatment,the irrigation level was 0.4 FC,and the fertilization levels were 9.6 kg/667m~2,38.4kg/667m~2,19.2kg/667m~2 and 28.8 kg/667m~2 at the rooting,seedling,flowering,and fruiting periods,respectively.