The Effects Of Fulvic Acid On The Structure Of Blacb Loessial Soil And Growth Characteristics Of Pakchoi

Fulvic acid is not only a soil amendment,but also regulates plant growth.In this paper,fulvic acid is used in black loessial soil in Changwu County,Shaanxi Province.Through indoor soil column and pot planting experiments,combined with mathematical model,the physical and chemical properties of fulvic acid on soil,water migration,nutrient leaching,growth of pakchoi and photosynthesis.The influence of characteristics is of great significance for improving the utilization rate of water and soil resources in the Loess Plateau and the yield of crops.The main results are as follows:?1?Appropriate amount of fulvic acid can effectively improve soil aggregate structure,enhance soil colloid stability,reduce soil bulk density and compactness.The average geometric diameter of the soil increased,and the unstable aggregate index,fractal dimension,and erodibility factor decreased significantly?P<0.05?.After 20 days of cultivation,the bulk density of the treated soil at 1,4,and 8 g/kg decreased to 1.31,1.28,and 1.27 g/cm³.The absolute values of Zeta potential increased by 9.92%,18.91%,and 29.01%,respectively,with the increase of the content of fulvic acid The conductivity of the soil showed an upward trend;the pH of the soil did not change significantly.?2?Fulvic acid can improve soil water retention and water retention,reduce the fixation of soil particles to nutrients,and enhance the effectiveness of soil nutrients.The cumulative infiltration volume of 100,400,and 800 mg/L fulvic acid solution,and the migration rate of the wetting front decreased.After the infiltration,the soil moisture content of the soil column profile 0-22.5 cm increased.With the increase of fulvic acid content,the adsorption amount of soil particles to phosphorus during the isotherm adsorption process decreased significantly;the leaching concentration and cumulative leaching amount of ammonium nitrogen,nitrate nitrogen,and phosphorus in the leaching process continued to increase;the leaching outflow The volume of the liquid decreases,and the fulvic acid in the shower solution contains a large number of acidic groups such as carboxyl groups and hydroxyl groups,resulting in a decrease in the pH of the shower solution and an increase in electrical conductivity.?3?Fulvic acid can promote the growth of pakchoi.Spraying at low concentration?100,400 mg/L?is beneficial to improve the quality of pakchoi.The plant height,leaf area,above-ground and underground biomass,root-to-root ratio increased with bottom application and spray application.The spraying concentration of 400 mg/L had the best effect on leaf area and chlorophyll promotion.Spraying 800 mg/L had the highest biomass and root-to-root ratio.The Logistic growth curve model can highly simulate the changes in plant height and leaf area.The plant height,leaf area maximum growth amount k,growth rate coefficient b,and fast-growing period growth amount I all increase.Humic acid has a significant effect on the total duration of the fast-growing period,and spraying mainly affects the maximum growth rate of the fast-growing period.Spraying 100 and 400 mg/L can increase the content of soluble sugar,protein,and vitamin C.If the spraying concentration is too high at 800 mg/L,salt stress will occur,and the three quality indicators of pakchoi will all decrease.?4?Fulvic acid can inhibit the transpiration of pakchoi,adjust the stomatal conductance of pakchoi,reduce crop water loss,and improve the water use efficiency of pakchoi.With the increase of the bottom application level,the transpiration rate decreased,the net photosynthetic rate increased,the intercellular CO₂ concentration and stomatal conductance increased first and then decreased;with the increase of the spraying concentration,the intercellular CO₂concentration increased significantly Larger,the transpiration rate decreases,stomatal conductance decrease,increases first and then decreases.?5?Non-right-angle hyperbola,right-angle hyperbola,binomial regression and exponential models can all highly fit the changing process of the light response curve of Chinese cabbage.In the exponential model,the light compensation point and light saturation point of the bottom treatment increase,but decrease after the spray treatment,and the maximum photosynthesis rate and apparent quantum efficiency are opposite.The daily change curve of photosynthesis of Pakchoi has a double-peak shape.The 400and 800 mg/L spraying treatment can significantly reduce the photosynthetic rate and transpiration rate of the leaves during daily changes.100 mg/L spraying treatment had the most significant effect on the photosynthetic rate of the whole day,while the bottom application had a significant effect on the photosynthetic rate of the leaves from 12:00 to 16:00.The photosynthetic rate of spraying treatment at 12:00 was significantly higher than the control group;foliar spraying 400 and 800 mg/L could effectively inhibit the leaf transpiration rate.At12:00,the transpiration rate only reached 66.43%and 50.85%of the control group.Help plants maintain moisture and material accumulation.