Effect Of Pressure Head On Soil Nitrogen Transport And Vegetable Nitrogen Use Under Moistube Irrigation And Fertilization

Moistube irrigation and fertilization technology is a technological innovation to realize comprehensive benefits such as water saving,fertilizer saving and high yield in the face of the current situation of water shortage,excessive water consumption in agriculture and fertilizer abuse in China.At present,there are few theoretical researches and production applications on this technology.In order to enrich the research of this technology and lay a foundation for its further popularization and application,this paper focuses on the study of the law of soil water and nitrogen transport under the condition of moistube irrigation and fertilization and explores the irrigation mechanism and application effect of moistube irrigation and fertilization technology.In this experiment,urea analytical pure was selected as fertilizer.Through indoor soil box test and greenhouse pepper planting test,the influence of pressure head on soil water and nitrogen transport and vegetable nitrogen utilization under the mode of moistube irrigation and fertilization were explored under the same fertilization concentration.With the help of indoor soil box test,the soil moisture and nitrogen transport process under the condition of moistube fertilizer solution infiltration was simulated.Six pressure heads,0.75 m,1 m,1.25 m,1.5 m,1.75 m and 2 m,were set in the experiment.The concentration of fertilizer solution was set at1000 mg/L,the buried depth of moistube was 20 cm,and the irrigation period was 108 h.By observing the cumulative infiltration amount,wetting front shape and movement,soil moisture distribution and content under different pressure heads,the law of soil moisture movement,the dynamic change of soil moisture content with time and its response to different pressure heads were explored.In addition,by observing the distribution and content of ammonium nitrogen and nitrate nitrogen in soil under different water heads,the distribution law of soil nitrogen and its dynamic change characteristics were explored.The results showed that under the condition of moistube fertilizer solution infiltration,the cumulative infiltration amount of each treatment showed an increasing trend with the prolonging of infiltration time,and increased with the raising of pressure head.With the infiltration of fertilizer solution,the shape of the soilwetting front was approximately a circle centered on the location of the moistube,moving faster in the vertical and horizontal directions,and the soil wetting area gradually increased with the increase of pressure head.The soil moisture content,ammonium nitrogen and nitrate nitrogen content at the infiltration interface of fertilizer solution were the highest,and gradually decreased with the extension of the distance from the infiltration interface.Soil moisture content and nitrate nitrogen content at the same location increased with the increase of pressure head,while ammonium nitrogen content at the same location increased first and then decreased with the increase of pressure head.Pepper planting experiments were carried out in plastic greenhouses.Two kinds of pressure heads of 1.5 m and 2 m were set in the experiments.The experiments were carried out under the conditions of 0,500 mg/L,1000 mg/L of fertilizer concentration and 20 cm of the buried depth of moistube.A total of 6groups of treatments were carried out.By observing the cumulative infiltration amount,soil moisture content,soil ammonium nitrogen and nitrate nitrogen contents of different treatments and their dynamic changes with the duration of fertilizer application,the influence of pressure head on soil water nitrogen content and its changes were explored.In addition,by measuring the total nitrogen content,fresh weight and dry matter accumulation of roots,stems,leaves and other organs during the growth period of pepper under different treatments,the absorption and utilization of nitrogen by plants and their response to pressure head were explored.Last but not least,by comparing pepper yield,water content and nitrogen use efficiency,the influence of pressure head on the application effect of moistube irrigation and fertilization technology was explored,and a suitable npressure head for pepper growth and high efficiency of water and fertilizer use was sought.The results showed that the cumulative infiltration amount,soil moisture content and ammonium nitrogen content of 2 m pressure head treatment were higher than those of treatment under 1.5 m pressure head at the same fertilizer concentration,and the accumulation of nitrate nitrogen in soil was accelerated,but the content was not significantly different from that of 1.5 m treatment.Nitrogen accumulation in root,stem,leaf and other organs of the plant was in the order of leaf > stem >root,and the dry matter accumulation was in the order of stem > leaf > root,and2 m pressure head treatment was beneficial to increase nitrogen accumulation,fresh weight and matter accumulation of the plant.The yield per plant treated with 2 m water head was relatively high,which was 1.50,1.39 and 1.49 times of which treated with 1.5 m corresponding concentration respectively,and the water and nitrogen utilization were also relatively high.