| The northeast black earth area as one of the four big black soil area,the soil is fertile and organic matter,nutrient content is high which is conducive to crop growth and development.Therefore,it is one of the important commodity grain base in China.To ensure the food and food safety of our country,northeast black earth area plays a significant role,but water and soil loss in northeast China is serious in recent years,soil bulk density increases,the water conservation capacity decreases.All these results a serious decline in crop production which is a serious threat to the food security in our country,also brings bad influence to our country food exports.Now the soil and water loss area in northeast black earth area has reached a total area of about a quarter of the soil,so the governance of the looming problem of soil and water loss control in northeast black soil area has received wide attention by everyone and is listed as one of the key work.The production materials of biochar is animal manure,straw and other renewable resources,the preparation of it greatly reduces the behavior of pollution to the environment such as the burning of straw,and biochar can effectively improve soil porosity,raise soil conservation performance,achieve the effect of water production.Therefore,in the northeast black earth area applying experiments of biochar can effectively find the governance effect on the northeast black soil by adding biochar and foreshadow for wide use.So this experiment was conducted in the beian hongxing farm in heilongjiang province where is a typical northeast black soil area,adopt the method of field trials for three consecutive years and applied four different levels of biochar in soil.The soil basic properties index,soil water movement and solute transport parameters were measured,the change rule of the indicators under different applying biochar for three consecutive years was analysed,the model of soil water movement and solute transport was set up and the model of simulation on soil water movement and solute transport under experimental conditions was verified.The preliminary conclusions are as follows:(1)The application of biochar can effectively reduce the soil bulk density and increase soil porosity,and there is a negative correlation relationship between the size of biochar soil bulk density and addition of biochar while is a positive correlation between the soil porosity and biochar.In the three consecutive years,the soil bulk density decreased by 7.21%,9.89%and 12.69%respectively,and the porosity was up to 12.90%,18.62%and 21.01%separately.Therefore,the application of biochar can effectively improve the soil conditions and improve the effect of biochar with the increase of the year.(2)The impact of biochar on soil water holding capacity do not present certain regularity,in the first year with the increase of applying content of biochar,field capacity showed a trend of increase,but in the second year and third year,it first increased and then decreased.The wilting coefficient under different amount of biochar showed the regularity of first increase then decrease,and the maximum wilting coefficient was increased with the increase of applying year of biochar.The growth rate of soil saturated water content in the first year was 2.73%to 9.55%,6.93%to 12.93%in the second year,and 7.55~13.04%in the third year.Biochar can effectively improve soil water holding capacity and thus achieve the goal of water-saving and increasing production.(3)The soil water characteristic curves under different biochar conditions were higher than those without biochar,and the soil moisture content was positively correlated with the amount of biochar.Simulation parameters of soil water characteristic curve,?_S??in relation with biochar content were positively correlated,but?r?n were in contrast.The variation of the inlet value with the change of applying biochar content in all the parameters is the largest.And under the condition of applying biochar for successive years,the difference between each process of soil water characteristic curve increased,the change trend of each parameters also increased.Biochar application can effectively improve the soil moisture diffusivity,and based on the fitting of soil moisture diffusivity and soil moisture content,there was a exponential function relationship between them and achieved good fitting precision.Unsaturated soil hydraulic conductivity increased with the increase of applying biochar content and with the increase of biochar application year its increase rate showed a trend of increase,for detailed the first year increased by 13.04%~13.04%,increased by 69.57%~69.57%of the second year,third year increased by 139.13%~139.13%.Hydrodynamic dispersion coefficient of soil with biochar seems existing a positive correlation relationship,and through the fitting result we found that with the increase of applying biochar content,Dsh and moisture movement speed was on the rise,while the soil penetration time was reduced.And when biochar quantity was more than 50 t/hm2,the increasing trend of the rate of hydrodynamic dispersion coefficient of soil slowed down.Biochar application can effectively improve the soil water-holding capacity and water movement and solute transport parameters,and with the increase of biochar application of the year,the rate of increase trend remains unchanged but the rate reduced.(4)Based on the soil water dynamics and the local soil characteristics,the initial and boundary conditions of soil water movement and solute transport were determined,and the model was established according to the preliminary parameters of soil water movement and solute transport which were measured previously.Then through the contrast of the simulation value and the measured values of the moisture content of soil profile and the content of soil solute and after 20min,1 h and 12 h of a rain,determined its error within the scope of the permit which showed that this model was suitable for the experiment of the research on the simulation on oil water movement and solute transport under the condition of applying biochar for consecutive years.(5)The result of the simulation showed that the soil water content increased with the increase of the depth during 0 to 40 cm under the condition of applying different biochar content,while in the 40 cm-80 cm showed a opposite trend,but soil solute content decreased with soil depth during0 to 30 cm and the opposite trend appears when the depth was 30 cm-80 cm.Then,the numerical of soil moisture and solute did not change when the depth of soil reaching 80cm.In addition,the order from big to small of soil water and solute content is both C4,C3,and C2,C1,and CK,and with the increase of biochar application year,the difference in value between the soil moisture and solute content under the treatments of applying different content of biochar were increased,but the growth rate reduced,this is because the biochar soil have a cumulative effect but the effect exists a certain extent.Biochar can effectively maintain soil moisture and solute in soil,which is of great significance to the cultivation of crops. |
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