Effects Of Differeeffects Of Different Components Of Humic Acid On Soil Water Movement With Physical And Chemical Properties

Humic acid and fulvic acid are important components of humic acid.Due to the huge difference in their molecular structure and composition,they play different roles in soil properties.In this paper,humic acid and fulvic acid are used in the black loess soil in Changwu County,Shaanxi Province.Through one-dimensional vertical infiltration,soil moisture constant,soil cultivation and other experiments,combined with mathematical models to analyze the effect of humic acid on soil moisture movement and water retention Characteristics,basic soil properties,available nutrients,surface electrochemical properties,etc.The physicochemical properties of humic acid and fulvic acid on the soil-water relationship were explored,The main research results are as follows:(1)Humic acid promoted the reduction of bulk density better than fulvic acid,and soil bulk density was significantly negatively correlated with soil humic acid content(P<0.05).The effects of fulvic acid treatment groups on the soil water stability of large aggregates were more significant.The 5%content level of fulvic acid has a better improvement effect on the soil water stability of large aggregates,and significantly reduces the fractal dimension of the soil.As far as different components of humic acid can increase soil moisture constant,the difference between HA and FA treatments is not significant(P>0.05).Moderate soil humic acid content can increase soil moisture infiltration rate.The increase in the level of soil fulvic acid increases the water holding capacity of the soil and slows down the process of soil water movement.The three entropy infiltration models,E-Horton,E-Kostiakov,and E-Philip,have a fitting degree R2 greater than 0.95.The fitting confidence is high,and they can describe the law of soil moisture infiltration process well.The soil moisture characteristic curve shifts to the right with the increase of humic acid content.(2)The different components of humic acid can adjust the pH of the soil with acid,adjust alkali and stabilize the buffer function.The content of soil humic acid has a positive correlation with the content of CEC,and the change of EC is not significant.,Can increase the content of soil OC.The content of fulvic acid presents a continuous downward trend to the pH value,reaching a significant level.(P<0.05).It has a significant positive correlation with CEC and EC,and has no significant effect on soil organic carbon.After urea and superphosphate were applied to the soil for 30 days,humic acid reached the promotion effect when the applied amount was 2%,the ammonium nitrogen content showed a slow increase trend,and the nitrate nitrogen changed between 3%-10%.Obviously increasing trend,fulvic acid can significantly increase the available phosphorus content when the content is 1%,and the soil ammonium nitrogen content is significantly positively correlated with soil fulvic acid.There is a positive correlation between soil available phosphorus content and soil humic acid.When humic acid itself has corresponding metal elements,adding to the soil increases the water-soluble salt content of the soil itself.The effects of different components of soil humic acid on the poor electrochemical properties of the soil surface are consistent,and they can all increase the soil surface potential and specific surface area;weaken the soil surface charge density and surface electric field,and the effect of fulvic acid is more significant.(3)With the passage of the test time,In the range of 2%test content,the soil conductivity showed a fluctuating upward trend,and the change range was not significant.Among the fulvic acid treatment groups,the pH value dropped rapidly at the initial stage,and slowly rose and became flat at the later stage of the culture.The electrical conductivity showed an "N"-shaped change trend.The CEC showed the same change trend during the cultivation process.It was higher than that of the CK group at 90 days,and the soil organic carbon content increased.Within 5%,the short test time did not cause the accumulation of OC.After applying basal fertilizer,the content of ammonium nitrogen increased rapidly within 3 days of pre-cultivation,and then rapidly decreased to nearly flat,indicating that the application of humic acid can increase the content of soil ammonium nitrogen,and the nitrogen increase and ammonium retention of fulvic acid are slow.The release effect is better.The content of nitrate nitrogen continues to increase.The effect of fulvic acid is more significant than that of humic acid(P<0.05).After the end of the culture,it is higher than the initial CK level.On the whole,the water-soluble salt content of the soil does not change regularly over time.After the different components of humic acid are applied to the soil,the electrochemical properties of the soil surface fluctuate within a certain range over time.The incubation time does not have obvious characteristic laws on the surface potential,surface charge density and surface potential of the soil.The specific surface area of the soil first increases and then decreases and tends to be stable.The effect of fulvic acid is more significant.