Effects Of Soil Particle Interaction On The Stability Of Lou Soil Aggregates And Phosphorus Loss Under Different Fertilizer Application Modes

Soil erosion and nutrient loss have always been environmental issues that have attracted much attention.Soil and nutrient loss during rainfall is largely affected by the stability of aggregates.Most of the researches have reported the important effect of soil fertilization on improving the stability of aggregates from macro-scale,while the researches in recent years think that the interaction between soil particles at meso-scale may play a decisive role on the stability of aggregates.Based on this,the field fertilization with chemical fertilizer and indoor simulated fertilization with organic materials were selected as the research objects in this study.Through the characterization of surface properties,the interaction forces between soil particles were calculated quantitatively,and the aggregate stability test and rainfall simulation test were conducted to reveal the internal control mechanism of soil fertilization on aggregate stability and phosphorus loss.The main research results are as follows:The characteristics of soil aggregate stability,soil loss and phosphorus loss and the relationship between soil aggregate stability and phosphorus loss and soil grain interaction under long-term positioning and different fertilization treatments were expounded.It was found that phosphorus application(NPK)weakens the electrochemical properties of the soil surface and thus reduces the electrostatic repulsion between soil particles.At the same time,the soil Hamaker constant is increased,resulting in stronger van der Waals attraction between particles.The hydration repulsion is only related to the distance between particles;The net repulsive force(the combined force of electrostatic repulsion,Van der Waals attraction,and hydration repulsion)was expressed as a repulsive force,and the net repulsive force without phosphorus treatment(NK)was stronger.There was an exponential positive growth between the release of soil aggregate micro-particles and the net repulsion between soil particles.The NPK treatment had weaker net repulsion between particles and less release of aggregate particles,thus significantly reducing the loss of soil particles and particulate phosphorus.The loss of dissolved phosphorus is affected by the repulsion between soil particles and phosphorus levels.Phosphorus application will increase the risk of loss of dissolved phosphorus in runoff.The stability of Lou soil aggregates,the loss characteristics of soil particles,particulate phosphorus and dissolved phosphorus and the relationship between them and the interaction of soil particles under the treatment of straw and biochar were revealed.It is found that:(1)Compared with the control(CK,without adding straw or biochar),the treatment with biochar(TBR)/ straw(TSR)increased the specific surface area and surface charge, decreased the electrostatic repulsion force between soil particles,and also increased the Hamaker constant,thus increasing the van der Waals attraction between particles;The net force(repulsion)among soil particles is further weakened,among which TSR treatment has the weakest net repulsion among particles and CK treatment has the strongest net repulsion.There is an exponential positive correlation between aggregate crushing strength and net repulsive force,and the order of aggregate crushing strength and net repulsive force between soil particles is CK>TBR>TSR;TSR and TBR both reduce the net repulsion between soil particles and the release of aggregate particles,thus significantly reducing the loss of soil particles and phosphorus.The loss of soil particles,particulate phosphorus and dissolved phosphorus is CK>TBR>TSR,which is consistent with the net repulsion strength.In summary,the long-term combined application of nitrogen,phosphorus and potassium fertilizers as well as the indoor simulated fertilization with straw/biochar addition contributed to the improvement of soil aggregate stability and the alleviation of soil particulate and particulate phosphorus loss during rainfall through field localized fertilization and indoor simulated fertilization experiments.The action mechanism is that the surface property of the soil is changed by applying chemical fertilizers and adding organic materials for fertilizer so that the electrostatic repulsion is reduced,or the van der Waals attraction is enhanced,and finally the net repulsion between soil grains is weakened,so that the effects of improving the stability of aggregates,reducing the crushing of aggregates and further reducing the loss of soil grains and phosphorus are achieved.The research results will help to understand the phosphorus migration process in soil solid-liquid phases and its correlation with the interaction within soil particles and provide theoretical support for improving the aggregate stability,preventing and controlling soil erosion and phosphorus loss by soil fertilization.