| This paper analyzes the distribution rules and characteristics of different forms of organic phosphorus and inorganic phosphorus in soils on the north and south banks of the Wangbeng section of the Huaihe River Basin from the perspectives of space and soil depth,and conducts sampling analysis on the farmland ditches connecting the main stream of the Huaihe River to study the ditches.Phosphorus adsorption-release characteristics of sediments and the effect of farmland runoff inputting phosphorus into ditches;indoor simulation experiments are used to study the vertical transport loss of phosphorus in different soils under the conditions of natural state and artificial biochar addition performance.Based on the previous studies,the characteristics of phosphorus speciation activation and release were further studied under different concentrations of low-molecular-weight organic acids.The following conclusions can be drawn from the above research:(1)The maximum total phosphorus(TP)content on the south bank is 705 mg/kg,while the maximum TP content on the north bank is 1385.65 mg/kg,indicating that the soil on the north bank is more fertile and is more conducive to crop growth.The content of labile organic phosphorus(LOP)and moderately resistant organic phosphorus(MROP)in the soil on the north and south banks decreased with soil depth.As the south bank belongs to forest land,there is no plowing and fertilizing behavior.As crops are planted on the north bank,there are irregular plowing and fertilizing activities,which causes the soil on the south bank to infiltrate continuously under rainfall conditions,showing a phenomenon of high TP content in the deep layer.The content of various phosphorus on the north bank generally decreases with the deepening of the soil layer depth.(2)There is a process of adsorption and desorption between the overlying water and sediments in the typical ditches on the north and south banks,and the sediments on the south bank are more likely to adsorb phosphorus in the overlying water than on the north bank.The highest Fe/Al-P content on the south bank trench sediments is 718.52 mg/kg,the average Ca-P content is 722 mg/kg,and the north bank Fe/Al-P content is up to 1119 mg/kg,and the average Ca-P content is 577 mg/kg.On both sides,the larger the particle size of the former,the higher the content;the latter is the opposite.As the particle size decreases,the content of organic phosphorus on the north and south banks is higher.It shows that the amount of bioavailable phosphorus lost in the farmland around the north bank ditches is relatively high.(3)Under natural leaching,the concentration of TP on the south bank has a downward trend,while the concentration of soluble resistant phosphorus(SRP)gradually rises,and the change trends of dissolved total phosphorus(DTP)and SRP in the two places are similar.Under the condition of artificial regulation,the TP concentration on the north bank did not increase significantly compared with the natural state,and the TP concentration on the south bank was slightly higher than the natural state.It shows that the addition of biochar has a good effect on stabilizing soil pH.(4)Malic acid has a higher activation rate of organic phosphorus(OP)on the north bank than on the south bank.The Fe/Al-P in the south bank has a good activation effect at low concentrations,and high concentrations are prone to inhibiting effects.Ca-P has a better activation effect at low and medium concentrations.The Fe/Al-P in the north bank is opposite to the soil in the south bank,and the activation rate can reach 68%under high concentrations of malic acid.The activation of citric acid on the soil on the south bank shows that the low-medium concentration is better than the high-concentration,while the high concentration on the north bank has the advantage of activation.For Fe/Al-P,the soil on the south bank has a good activation effect at a medium concentration,and the north bank has a medium-high concentration.The concentration is better;for Ca-P,the activation rate of the soil on the south bank can reach about 90%under the three concentrations,and the maximum on the north bank can only reach about 65%.Low-molecular-weight organic acids have a good role in promoting the conversion of unavailable phosphorus to biologically available phosphorus in the soil,and can further promote the growth of crops.Figure[85]table[46]reference[110]... |
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