Effect Of Organic Matter On Phosphorus Adsorption-desorption Characteristics Of Black Soil

Organic matter is one of the most important factors affecting Phosphorus(P)adsorption and desorption,and there are great differences in P adsorption and desorption results under the effects of organic matter in soil.The effects of organic matter on P adsorption and desorption characteristics of typical black soil were systematically studied,considering both internal and external organic matter,so as to clarify the mechanism of P supply and storage in soil,to realize the goal of reducing fertilizer application and increasing fertilizer efficiency and the recycling of organic materials.The main obtained results were as follows:(1)By analyzing the correlation between the maximum adsorption amount of five black soils and the soil organic matter contents,it is found that the higher the soil organic matter content,the lower the ability to absorb P.On this basis,the black soil collected from the experimental field of Jilin University was selected as the research object.The organic matter in the soil was removed by different chemical extraction methods,and then the adsorption and desorption experiments were combined to study the effect of soil organic matter on phosphorus adsorption and desorption.The results showed that compared with the control soil,the maximum P adsorption capacity of soil was enhanced after removing some organic matter by different extraction methods,constant of P adsorption bonding energy and maximum buffering capacities was decreased,and the desorption capacity of P was decreased.The maximum buffer capacity of P decreases by about 32%,and the rate of P desorption has dropped by 61%.In view of these,the retention ability of P is still improved.The removal of organic matter weakens the supply capacity of phosphorus,which indirectly indicates that the presence of soil organic matter can improve the supply capacity of phosphorus.(2)Adding exogenous organic materials,manure and biosolids to the black soil of Jilin University Agricultural Experimental Base,adding 3 gradients of 5g/kg,10g/kg and 20g/kg.After 30 days incubation of exogenous organic materials,the soil organic matter content increased with the increasing of the amount of cattle manure and biosolids applied,but the P adsorption capacity of soil decreased with the increasing of organic matter,the maximum P adsorption capacity of soil was decreased by 18%-46%;At the same time,the desorption rate was higher than that without exogenous organic materials applied.Therefore,exogenous organic matter has an inhibitory effect on soil phosphorus adsorption,but promoted desorbing of soil P,and increased the supply capacity of P.(3)After the incubation of organic materials applied in soil for 24 hours,the corn pot experiments were carried out to investigate the effect of exogenous organic materials on phosphorus uptake.The results showed that with the application of exogenous organic materials such as cattle manure and biosolids,the contents of soil organic matter and Olsen-P increased,and the total phosphorus uptake and net phosphorus uptake of the plants increased.At the same time,with the growth of plants,the proportion of Olsen-P in total P in soil is also increased.The P adsorption and desorption experiments of soils before and after corn pot experiment showed that the maximum P adsorption capacity of soil in the control soil increased after potting,however,the maximum P adsorption capacity of soil decreased after the addition of organic matter,and the more the organic matter was added,the greater the decrease of the maximum P adsorption capacity of soil and the increase of the soil phosphorus desorption rate,indicating that the addition of organic matter enhanced the phosphorus supply capacity of the soil,thereby increasing the phosphorus absorption of the plant.In summary,whether it is the application of exogenous organic materials to increase soil organic matter in a short period of time,or the soil with relatively high soil organic matter itself,its adsorption capacity for phosphorus is relatively lower,but the desorption capacity is higher.Therefore,it can be concluded that in the process of plant growth,the desorption capacity of phosphorus can be increased by applying an appropriate amount of organic fertilizer or by the other methods of increasing soil organic matter,thereby the utilization rate of phosphorus in the soil will also increase.