Effects Of Earthworm Droppings On Soil Water And Nitrogen Transport And Its Parameters Major

Nitrogen can accelerate plant cell division,the growth rate,and participate in various physiological processes of plants.However,the unreasonable application of nitrogen fertilizer results in the excessive application of nitrogen to the soil.This approach can lead to nitrogen loss in farmland,which has a significant impact on agricultural production and the ecological environment.Therefore,controlling the loss of nitrogen elements in farmland has become an urgent and necessary task.This article focuses on earthworm casts as the research object and employs a combination of indoor soil column experiments and model fitting methods to investigate the changes in soil infiltration characteristics,as well as water and nitrogen transport,under various conditions.These conditions include different earthworm casts to soil mass ratios(0,1/20,1/15,1/10,1/5),the same earthworm casts application ratio(1/10),different nitrogen fertilizer concentrations(0.5 g/L,1.0 g/L,2.0 g/L),and different earthworm casts application positions(0-10 cm,5-15 cm,10-20 cm,15-25 cm).Furthermore,the article simultaneously analyzes the changes in solute penetration curves and water characteristic curves under different application ratios of earthworm casts.The main research results are as follows:(1)Under waterlogged infiltration conditions,earthworm casts increases the soil’s infiltration capacity and cumulative infiltration due to its good pore structure.The transport distance of the wet front decreases to varying degrees with the increase in the proportion of earthworm casts applied.However,all treatment groups had greater transport distances compared to the control group,with the 1/20 treatment group exhibiting the most significant transport distance of the wet front.The Philip、Kostiakov and Horton models can all effectively simulate the change process of cumulative infiltration in each treatment group.Earthworm casts enhances the soil’s water holding capacity,and the water holding capacity becomes stronger with a higher application ratio.Additionally,earthworm casts increases the content of nitrate and ammonium nitrogen in the soil.As the proportion of earthworm casts applied increases,the content of ammonium nitrogen and nitrate nitrogen also increases.(2)Under different nitrogen fertilizer application rates,the treatment group treated with earthworm casts exhibited an increase in cumulative infiltration amount,infiltration rate,and transport distance of the wetting front.When the proportion of earthworm casts application is 0 or 1/10,the infiltration rate(S)in the Philip and Kostiakov models show a positive correlation with the increase in nitrogen fertilizer application.Under different nitrogen fertilizer application rates,earthworm casts can increase the soil profile moisture content,as well as the content of nitrate nitrogen and ammonium nitrogen.When the nitrogen fertilizer application rates are 2.0 g/L,1.0 g/L,and 0.5 g/L,with a proportion of earthworm casts application at 1/10,the treatment group with earthworm casts shows significant improvements.In comparison to the treatment group without earthworm casts,the average volume moisture content of each soil layer increases by 15.68%,14.92%,and 15.32%,respectively.Additionally,the average nitrate nitrogen content increases by 46.59%,39.82%,and 32.56%,while the average ammonium nitrogen content increases by 57.31%,53.50%,and 56.11%.(3)Among different application positions,the treatment group with earthworm casts applied at 0-10cm showed the most significant effect,resulting in a substantial increase in the transport distance of the soil wetting front.However,as the application position deepened,the infiltration rate significantly decreased compared to the treatment group applied at the surface layer.The wetting front of the C2,C3,and C4 treatment groups decreased by 5.02%,13.39%,and 18.41%,respectively,compared to C1.During the water infiltration process,the application layer of earthworm casts accumulates a considerable amount of water due to its porous structure,which affects water distribution.Applying earthworm casts on the surface layer promotes water infiltration,while applying it on the bottom layer inhibits soil water infiltration.Furthermore,the application layer of earthworm casts significantly increases the soil moisture content.The content of ammonium nitrogen in the surface treatment group treated with earthworm casts was significantly higher than in other treatment groups.However,the treatment group applied at the bottom also increased the content of ammonium nitrogen in the applied layer of earthworm casts accordingly.Moreover,the treatment group applied to the surface also reduced the loss of ammonium nitrogen due to its inhibitory effect on soil evaporation.(4)The application of earthworm casts to the soil enhances its water retention capacity.The higher the application ratio,the greater the soil volume moisture content under the same soil water suction.Under the condition of a water suction of 800 cm,the treatment groups increased by 6.67%,16.67%,23.33%,and 28.89%compared to the CK group,respectively.The Van Genuchten model can effectively simulate the impact of different application ratios of earthworm casts on the water characteristic curve.All parameters are positively correlated and increase with the increase in the earthworm casts application ratio.After comparing the fitting results of the models,it was found that the two-zone model has higher fitting accuracy than the CDE equation.By analyzing the fitted parameters,it was observed that as the proportion of earthworm casts applied increased,the average pore water flow rate decreased in a negative correlation.Compared to CK,the hydrodynamic dispersion coefficient,dispersion degree,and mass exchange coefficient increased by 50.00%,51.11%,and 126.21%,respectively.The soil moisture content increased by 16.48%in the mobile water bodies,which had a significant impact.