| Water and fertilizer are the two main factors that restrict the growth of crops.In the actual field operation,the traditional irrigation and fertilization mode has a low efficiency in the utilization of water and fertilizer resources.The unreasonable application of water and fertilizer resources will not only cause waste of resources,but also is not conducive to environmental protection,and seriously hinder the sustainable development of agriculture.Therefore,it is necessary to improve the existing irrigation mode for China’s agricultural development The way to go.The integrated technology of water and fertilizer can provide a new way for the agricultural development of our country from the extensive type of large water and fertilizer to the intensive production of rational utilization of resources.As a new type of underground moistube irrigation technology,moistube run irrigation can provide an effective carrier for the integration of water and fertilizer.The water and fertilizer integration of micro-irrigation uses the water potential difference between the inside and outside of the membrane of the buried micro run pipe to directly transport the dissolved fertilizer to the root of the crop,and the water and nutrient supplied to the crop can achieve the synchronous coupling effect in time and space.In order to explore the influence of different nitrogen application levels on soil water and nitrogen transport under the condition of moistube run irrigation,and to explore the influence of integrated nitrogen application level of moistube run irrigation on the growth,yield,soil moisture content and water use efficiency of vegetables,and to explore the law of water and fertilizer demand for vegetable planting under the condition of water and fertilizer integration of moistube run irrigation,respectively,carry out indoor soil box nitrogen solution infiltration simulation test Test and outdoor vegetable planting test.The spacing between the micro moistening pipes in the indoor soil box simulation test is 30 cm,and the buried depth of the micro moistening pipes is 20 cm,set four nitrogen application levels: 0 mg/L,500 mg/L,1000mg/L,1500mg/L,to explore the change of cumulative infiltration amount,soil moisture content,distribution of soil nitrogen,shape and size of wetting body,migration distance and speed of wetting front with infiltration time under the same waterhead and same infiltration time under different nitrogen application levels of moistube irrigation.The results show that: under the working head of moistube irrigation,the cumulative infiltration amount of each fertilizer concentration level increases nonlinearly with the infiltration time,and its correlation satisfies the quadratic equation of one variable;under each treatment,the wetting front presents an approximate ellipse with the direction perpendicular to the micro lubrication pipe as the longer axis,and the water square direction of the micro lubrication pipe as the shorter axis;within 36 hours of infiltration,the migration distance of the wetting front changes with time At the end of moistube irrigation,the farther the moisture content of the two-dimensional section is from the center of the moistube irrigation pipe,the lower the moisture content of the soil,the accumulation area of nitrate nitrogen and ammonium nitrogen will be formed.The higher the nitrogen application level,the soil moisture content and nitrate at the same point of the wet section The spatial and temporal distribution characteristics of soil water and nitrogen in vertical one dimension: within three days of continuous irrigation,the change of soil water content outside the wetting front is small,always close to the initial soil water content.5-7 days after the end of irrigation,the soil moisture content of each soil layer is still slowly increased,and the moisture in the wet body is still migrating;within 5-7days after the end of continuous irrigation,the nitrate nitrogen in the wet body is still migrating,and the nitrate nitrogen content in the clear water irrigation within 10 cm from the micro run pipe decreases with the infiltration time,while the nitrate nitrogen content in the fertilization condition increases with the infiltration time.Under the condition of fertilization,the peak value of nitrate nitrogen content moved away from the micro run pipe with infiltration time.The higher the level of nitrogen application,the higher the content of nitrate nitrogen.Within 5-7 days after the end of continuous irrigation,the nearer the center of the micro run pipe,the lower the content of ammonium nitrogen.At the same time,the longer the infiltration time,the lower the content of ammonium nitrogen.As the infiltration time goes on,the position of the peak value of ammonium nitrogen content of each fertilization treatment is constantly changing,which is manifested as infiltration for 2-3 days,its peak value is about5 cm away from the micro run pipe,infiltration for 4-5 days,the peak value of ammonium nitrogen content is about 10 cm away from the micro run pipe,infiltration for 6-7 days,and its peak value migrates to 15 cm away from the micro run pipe.The experiment of vegetable planting can be divided into two parts: the experiment of Capsicum planting in greenhouse and the experiment of oilwheat vegetable planting in open air.(1)Three nitrogen application levels are set in the greenhouse pepper planting experiment: 0 mg/L,500 mg/L,1000 mg/L urea,pressure head is set with 1.5 m,2 m,there are six groups of experimental treatment,two micro moistening pipes are laid,and the buried depth of micro moistening pipes is 20 cm,the spacing is 25 cm.The results showed that the growth of pepper plants in greenhouse under 2 m pressure head was better than that under 1.5 m pressure head,and the growth and development of pepper plants under 500 mg/L fertilization treatment under the same pressure head was the best.(2)Four nitrogen application levels are set in the experiment of open-air oilwheat and vegetable planting: 0 mg/L,350 mg/L,700 mg/L,1050mg/L.the pressure head of each treatment is 1.5 m.Three micro moistening pipes with a buried depth of 15 cm are laid in the soil box with a spacing of 25 cm.The results showed that the growth and development of oilwheat vegetable was the best in the medium fertilizer treatment,and the most suitable nitrogen application level of oilwheat vegetable planted in the open air was about 700mg/L under the micro irrigation.It can be seen from the planting experiments of two different vegetables that the change of soil moisture content under the control of initial conditions such as pressure water head and micro run pipe buried depth is related to the type of test material,planting environment and nitrogen application level,especially the growth cycle of vegetables.Adding the corresponding amount of fertilizer in different stages of crop growth cycle can not only effectively improve the utilization rate of irrigation water,but also significantly increase crop yield. |
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