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Panax notoginseng is a highly regarded medicinal plant that has obstacles associated with continuous cropping. Understanding soil microorganisms is crucial, as they play a major role in this regard. However, soil microorganisms are affected by multiple factors; therefore, we need to conduct more in-depth research. This study investigated the combined effects of irrigation and microbial fertilizer treatments (J1F1, J1F2, J2F1, J2F2, J3F1, J3F2, and CK) on the diversity of bacterial and fungal microbial communities in the rhizosphere of Panax notoginseng. The bacterial 16S rRNA genes and fungal internal transcribed spacer (ITS) sequences were sequenced using Illumina HiSeq. The results showed that, without microbial fertilizer (CK), the microbial community abundance and diversity were significantly lower than in the other treatments; moreover, among the microbial fertilizer treatments, the microbial abundance in F1 was higher than that in F2. Under the same microbial fertilizer application, the incidence rate of Panax notoginseng root rot was J2 > J1 > J3, and the yield of Panax notoginseng was J3 > J2 > J1. Under the same irrigation conditions, the incidence rate of Panax notoginseng root rot was F1 > F2, and the yield of Panax notoginseng was F2 > F1. This study provides important guidance for Panax notoginseng plant microbiota and sustainable agriculture. [ABSTRACT FROM AUTHOR]

Plant-derived selenium is an important source of selenium (Se) for humans, which, however, has been restricted by a low content of Se in soil. Traditional Se fertilizers have tended to result in low selenium utilization. Thus, it was necessary to develop a new slow-release material to control Se fertilizer release. In this study, biochar pyrolyzed at 300 °C and 800 °C was cross-linked with polyethyleneimine (PEI) after being treated with HNO3 or NaOH (which were labeled Acid-W300, Acid-W800, Alkali-W300, and Alkali-W800). The results showed that the maximum adsorption capacities of Acid-W300, Alkali-W300, Acid-W800, and Alkali-W800 were 329.16 mg/g, 321.93 mg/g, 315.04 mg/g, and 344.33 mg/g, respectively. Among them, Acid-W800 and Alkali-W800 were mainly imine- and amide-bonded with SO32−, while Acid-W300 and Alkali-W300 were loaded with SO32− by forming the C–Se bonding as well as through imine- and amide-bonding. The release of four biochar-based selenium fertilizers in the red soil and brown soil extracts conformed to the pseudo-second-order kinetic model. The release rate and release amount of four biochar-based selenium fertilizers in the red soil extract were higher than those in the brown soil extract. Alkali-W800-Se had a higher proportion of Se-exchangeable release, accounting for 87.5% of the total loaded selenium, while Acid-W300-Se had the lowest proportion at 62.2%. However, the Se releases of Alkali-W800-Se were more than 42.49% and 37.67% of the total Se-loading capacity during 5 days of continuous red soil extraction and brown soil extraction, respectively. Acid-W300-Se released less than 20% of the total Se-loading capacity. Thus, Acid-W300-Se was the recommended slow-release Se fertilizer in red soil and brown soil. [ABSTRACT FROM AUTHOR]

The fungal community structure and soil fertility in rhizosphere soil have an important effect on the health of Panax notoginseng (P. notoginseng). The attack of pathogenic fungi and the imbalance of soil fertility can easily lead to diseases. The effect of Bacillus subtilis on improving the community structure of soil fungi has been confirmed, and the corresponding biological agent products have been commercialized. A pot experiment carried out in a greenhouse explored the effect of a biological agent and fertilizer on the fungal community in the rhizosphere of P. notoginseng. In the experiment, fertilization and the addition of biological agents were set up with three gradients, respectively, and the full coupling experiment was adopted, and the blank control group (CK) was set up at the same time. Therefore, there were thirteen treatments in the experiment. NH4 decreased between 36.42% and 11.56%, AP increased between 6.03% and 92.46%, AK increased between 2.99% and 25.40%, TN increased between 0.10% and 9.41%, and TP increased by 18.25% to 47.73% The addition of Bacillus subtilis biological agent decreased the Chao1, Shannon, Simpson, and ACE index of fungi in the rhizosphere soil of P. notoginseng. The Chao1 index decreased between 0.39% and 78.22%; the ACE index decreased between 0.43% and 78.24%. The main pathogenic fungi Cylindrocarpon and Fusarium of P. notoginseng were different in the experimental results. Cylindrocarpon decreased under F1C1, F2C1, and F3C2 treatments, while Fusarium increased under F1C1, F2C2, F3C1, and F3C3 treatments and decreased Fusarium content in rhizosphere soil of P. notoginseng in other treatments. RDA analysis (Redundancy analysis) showed that NH4-N was negatively correlated with the main pathogen Cylindrocarpon, Fusarium, and Ilyonectria, while AP and AK were positively correlated with Cylindrocarpon, Fusarium, and Ilyonectria. The results of the GRA-TOPSIS analysis showed that the score of F3C2 was the highest, while F2C3 and F2C1 ranked second and third, respectively. The calculation results of the theoretical model based on GRA-TOPSIS analysis showed that the GRA-TOPSIS score was highest when the theoretical optimal fertilizer application rate and bacteria application rate were 116.31 kg hm−2 and 15.83 kg hm−2, respectively. [ABSTRACT FROM AUTHOR]

For the realization of real-time detection of nitrogen concentration in the process of automatic mixed liquid fertilizer, a detection device was designed, which was mainly composed of a nitrate ion selective electrode, an electrode signal conditioning circuit, a temperature sensor, and a data acquisition and display circuit. There was a one-to-one correspondence between the response potential of a nitrate ion selective electrode and nitrate ion concentration. For this reason, the detection device could obtain the level of nitrate ion concentration by detecting the electrode's response potential, and then the nitrogen concentration of liquid fertilizer had been acquired indirectly. Measuring accuracy for the electrode's potential was a key influence factor of the device's performance. A 1 mV error of the electrode's potential led to a 4% concentration measuring error of monovalent ions. To evaluate the device's measuring accuracy for an electrode's potential, the electrode had been placed in a series of prepared potassium nitrate solutions whose NO3- concentration were 10-6, 5×10-6, 10-5, 5×10-5, 10-4, 5×10-4, 10-3, 5×10-3,10-2, 5×10-2, and 10-1 mol/L respectively, and the response potential of the electrode was measured by the device and a standard millivoltmeter PHS-3CT which was used as the comparative reference respectively, and it was known from the test results that the device's measuring result for the electrode's potential in each NO3- concentration was closed to that of PHS-3CT, and its maximum and minimum relative error were 5.2% and 1.2% respectively. Meanwhile, the response potential of the electrode would produce a temperature drift when the temperature varied, which would result in a measuring error of ion concentration. For reducing the influence of temperature variation, the electrode's temperature variability had been analyzed with 25°C as a reference, by measuring its response potential in a series of prepared solutions with different NO3- concentrations in the range of 10-5-10-1 mol/L and different temperatures within the scope of 5-45°C. The results showed that the response potential of the electrode had a linear change with the temperature difference of the solution to be examined and the maximum variability rate of the potential was 8.8%. Based on the response potential of the electrode measured in a series of prepared solutions with different NO3- concentrations and different temperatures, a temperature parameter model had been established by using the method of the least squares fitting step by step. Verification experiments of the temperature parameter model had been carried out, by using three kinds of prepared potassium nitrate solutions whose NONO3- concentration were 4×10-1, 4×10-2 and 4×10-3 mol·L-1 severally, and it turned out that the average relative measurement error and the maximum relative measurement error of the temperature parameter model were 4.49% and 9.2% separately. Furthermore, there may be some interfering ions (such as Cl-, SO4 2-, H2PO4 - and HPO4 2-) in a mixed liquid fertilizer in addition to NO3-, and the nitrate ion selective electrode had cross sensitivity. It would allow the electrode's response for interfering ions to come into being, which could bring about some impact on the device's measuring results. In order to determine the degree of influence of the interfering ions for the device's measuring results, the fixed interference method had been used to measure the electrode's selectivity coefficient for Cl-, SO4 2-, H2PO4-, and HPO4 2- respectively. The results indicated that the selectivity coefficient for 4 interfering ions were 5.1×10-2, 1.0×10-4, 2.0×10-4, and 5.0×10-5 singly, and that the bigger the selectivity coefficient was, the greater the impact of interfering ions on the electrode; moreover, it was found from experiments that the effects of interfering ions on the electrode weakened gradually with the decrease of the interfering ions concentration, and the measuring error of the device caused by Cl- was 4% when Cl-: NO3- = 1:100, that was to say, a small amount of interfering ions in a liquid fertilizer could not constitute a significant effect for the measured results. From the above, the device developed could meet the application requirements of a nitrogen concentration test in the process of automatically mixed fertilizer in engineering. [ABSTRACT FROM AUTHOR]

Improper irrigation by Panax notoginseng growers can lead to soil consolidation, low fertilizer utilization, and decreased yield quality. In an attempt to provide a scientific and theoretical basis for Panax notoginseng cultivation to improve soil microhabitat and yield quality, field experiment were conducted on three-year-old Panax notoginseng in 2019, 2020, and 2021. The experimental design consisted of two control factors, the amount of irrigation (W) and the amount of fertilizer (F) applied. The irrigation was set to three levels, as W1, W2, and W3, with exact irrigation volumes of 5 mm, 10 mm, and 15 mm. The amount of fertilizer applied was different in all four growth stages. The amount of fertilizer applied according to the four growth stages (rooting stage: seedling stage: flowering stage: fruiting stage), where F1 (360–360–360–360 kg∙hm−2), F2 (288–360–432–360 kg∙hm−2), F3 (216–432–432–360 kg∙hm−2) and F4 (144–576–288–432 kg∙hm−2). The W and F were randomly combined to form a total of 12 treatments. And a control treatment (CK), was added, and CK was neither irrigated nor fertilization. For obtaining the best treatment results, the TOPSIS method was used to comprehensively evaluate the soil microbial biomass carbon and nitrogen, enzyme activity, physiological growth and saponin content of Panax notoginseng in 13 different water and fertilizer treatments. The results indicated that microbial biomass carbon and nitrogen, urease, sucrase, acid phosphatase and catalase activities of Panax notoginseng soil were significantly different (P < 0.05) and varied with the growth stage. The comprehensive evaluation by the TOPSIS method ranked W3F4 first and was the optimal treatment. The W3F4 treatment was more beneficial to the quality of Panax notoginseng than the other 12 treatments. W3F4 had the largest soil microbial biomass carbon and nitrogen content. W3F4 had the highest urease, sucrase, acid phosphatase, and catalase activities, which were 1.95, 1.69, 2.32, and 1.47 times higher than the CK treatment, respectively. W3F4 significantly improved R 1 , Rg 1 , Re, Rb 1 , and Rd saponin content. This study provided a theoretical basis for the water and fertilizer regulation of Panax notoginseng with its green, healthy and efficient quality cultivation. • W3F4 treatment was most beneficial for the increase of ginsenoside content. • Soil microbial biomass C and N were negatively associated with Re, and were positively associated with R 1. • Soil water content, sucrase, acid phosphatase, catalase, and urease were negatively correlated with Rb 1. [ABSTRACT FROM AUTHOR]