Study On Soil Water And Nutrient Distribution Patterns Of Drip Irrigation And Fertilization

Drip irrigation is the use of plastic pipes to feed water to the root of a crop through a hole or drip in a hairline about 10 mm in diameter.It is one of the most effective water-saving irrigation methods in the current arid areas with a water utilization rate of up to 95%.Compared with sprinkler irrigation,drip irrigation has a higher effect on water saving and production increase,and can combine with fertilization to increase the fertilizer efficiency more than twice,etc.,which has been widely used in production practice.The soil column infiltration test membrane was carried out.Since the index of conductivity was used to indirectly reflect the soil concentration during the test,it was necessary to explore the influencing factors of conductivity in the process of infiltration.The dynamic changes and electrical conductivity during the infiltration of potassium sulfate solution with different concentrations(0,400,800mg/L)were studied,The following conclusions are drawn:1)the comprehensive evaluation of the influence degree of each factor on the electrical conductivity of a soil layer is the soil salt migration caused by the gravity of water content >temperature > before the soil reaches saturation in the infiltration process,which takes a short time;In the process of infiltration,soil salt migration caused by gravity after the soil reaches saturation > temperature > water content.In the process of drip irrigation,when the water head is constant,the time for the soil to reach saturation from the dry state accounts for a very small proportion in the whole process of drip irrigation,so the influence of water content on soil conductivity can be ignored,that is,the coupling of water content and conductivity need not be considered.2)in the process of infiltration,the conductivity of each soil layer shows a trend of increasing first and then decreasing,and the time of increasing stage is very short,while the time of decreasing stage is relatively stable and long.Under various concentrations,the peak of conductivity is at the radial 30 cm soil layer,but with the extension of infiltration time,the conductivity value of the 40 cm soil layer is the highest when it finally reaches the stable state.At the same time,it can be seen that the conductivity value of the 10 cm soil layer and the20 cm soil layer is close to each other.The conductivity of 30 cm soil is close to that of 40 cm soil.Moreover,the conductivity values of 20 cm and 30 cm differ greatly.Therefore,it can be inferred that during the infiltration of potassium fertilizer solution,the fertilizer mainly enriched between 10cm?20cm and 30cm?40cm.3)When the total salt content of the soil is 0.3%,the moisture content of each layer of the soil will gradually increase with the infiltration,and then remain relatively stable for a long time.When the irrigation stops for a certain time,the moisture content will slowlydecrease due to evaporation and seepage.When comparing 0.5% of total soil salt and 0.8% of total water in drip irrigation,the variation trend of water content was very similar in three different soil conditions with different total salt content.Therefore,it could be inferred that the nutrient content of the soil had little influence on the distribution of water content of the soil mass during the infiltration process.4)a three-dimensional isotropic homogeneous model for the transfer and transformation of soil water and potassium fertilizer is established,which can effectively reflect the transfer process of water potassium under the conditions of drip irrigation under the membrane;Through the test,the simulation and the measured values can be in good agreement,the simulated soil moisture content profile distribution is basically consistent with the measured values,and the relative error between the water content,conductivity and the measured values at each observation point is within 18%.At the end of the simulation results show that the drip irrigation,the soil moisture content decreases with the increase of the distance from head drops,mainly distributed in the quality of soil potassium sulfate concentration after fertigation from drops first 15 cm near 35 cm soil layer and soil layer,and increasing concentration with time is bigger,but the peak around 15 cm soil layer in 48 h,35 cm soil layer peak at about 72 h,then the quality of the various soil potassium in soil body concentration are increased with the increase of distance from dropping head showed a trend of decrease.