Optimization of Water and Fertilizer Management of Panax notoginseng Based on Changes in Soil Microbial Biomass Carbon and Nitrogen and Enzyme Activities

Abstract At present, there is a lack of understanding of the dynamic characteristics of the carbon, nitrogen, and enzyme activities of the soil microbial biomass of Panax notoginseng under irrigation and fertilization. We set up a field experiment with 3 irrigation and 4 fertilization levels for a total of 12 treatments plus a control in the micro-sprinkler Panax notoginseng farmland in Luxi County, Yunnan Province, from 2018 to 2020. The results showed that the soil microbial biomass carbon, nitrogen, and enzyme activities increased from the rooting period to the flowering period, and then decreased in the fruiting period.The soil microbial biomass carbon, nitrogen, and enzyme activities of Panax notoginseng reached the maximum values in the flowering period, while the minimum values were reached in the rooting period. There were significant positive correlations between the soil microbial biomass carbon and nitrogen and enzyme activities during different growth periods under different water and fertilizer optimization management. This study revealed the tendency of the carbon, nitrogen, and enzyme activities of the soil microbial biomass of Panax notoginseng with the growth periods. It also analyzed the optimal management of different water and fertilizer regimes and the Ci values of soil microbial biomass carbon, nitrogen, and enzyme activities in different growth periods to determine the best water and fertilizer treatment methods in each growth period through the entropy value method combined with the TOPSIS method. The study found that the Ci values changed with the change in the fertilization level under the same irrigation level. The Ci values decreased and then increased with increasing irrigation water under the same fertilization level. These results showed that, in terms of the effect of different water and fertilizer treatments on the regulation of the soil microbial biomass carbon, nitrogen, and enzyme activities in each growth period, the irrigation volume of 10 mm and fertilizer application of 8.00 kg.667− 1.m− 2 during the rooting period of Panax notoginseng were most effective, while an irrigation volume of 15 mm and fertilizer application of 8.00 kg.667− 1.m− 2 were more suitable for the seedling, flowering, and fruiting periods.