Effect Of Pressure Head On Soil Water And Nitrogen Migration And Greenhouse Vegetable Growth In Moistube-irrigation And Fertilization

Moistube irrigation and fertilization technology is a new type of irrigation and fertilization technology that combines moistube irrigation technology with water and fertilizer integration technology.With the help of this technology,the effects of water saving,fertilizer saving and yield increasing can be realized in agricultural production.At present,the theoretical research and application of this technology are relatively few.In order to enrich the theoretical framework of the technology and lay the foundation for its popularization,studied the application effect of moistube irrigation and fertilization technology and the distribution and migration of soil water and nitrogen under this irrigation and fertilization mode.Through greenhouse planting test and indoor soil box simulation test,pure urea was used as fertilizer to explore the influence of pressure water head on vegetable growth and soil water and nitrogen migration under the same fertilization concentration.Planting experiment of tomato and pakchoi was carried out in the greenhouse.The effects of pressure head on soil water and nitrogen transport were investigated by measuring the soil water content,ammonium and nitrate nitrogen content in each treatment.The effects of pressure water head on vegetable growth were investigated by measuring plant height,leaf area,fresh weight and other vegetable growth indexes.The irrigation water productivity,the agronomic use efficiency of nitrogen fertilizer and the contribution rate of fertilizer yield increase were calculated and the pressure water head suitable for the growth of different vegetables(tomato and pakchoi)with higher water and fertilizer use efficiency was found.In greenhouse planting test,two moistubes were buried in each box,with an interval of 30 cm and a buried depth of 20 cm.(1)Two groups of pressure water heads,1.5 m and 2.0 m,were set for tomato planting experiment in greenhouse,and the experiment was carried out at 0mg/L,400 mg/L and 800 mg/L of nitrogen application.In greenhouse planting test,two moistubes were laid in each box,with an interval of 30 cm and a buried depth of 20 cm.(1)Two groups of pressure water heads,1.5 m and 2.0 m,were set for tomato planting experiment in greenhouse,and the experiment was carried out at 0 mg/L,400 mg/L and 800mg/L of nitrogen application.It was found that 800 mg/L of fertilization concentration had better growth status and water and fertilizer utilization effect.Under this fertilization concentration,the tomato yield and utilization efficiency of irrigation water were the highest with 2.0 m of pressure water head.Therefore,2.0 m pressure water head and 800 mg/L fertilization concentration are more suitable for tomato growth in greenhouses.(2)The pressure water head was set at 1.0 m and 1.5 m,and nitrogen fertilizer with concentrations of0 mg/L,400 mg/L and 800 mg/L was applied respectively in the planting experiment of pakchoi in greenhouse.The results showed that the change of soil water content was in line with the water requirement of pakchoi.Soil water content and nitrogen content under 1.5 m water head treatment were higher than those under 1.0 m water head treatment.Fertilization concentration of 400 mg/L promoted the growth of pakchoi more obviously.Under the same fertilization concentration,the growth situation of pakchoi under 1.0 m pressure head was better,and the yield was higher,which could achieve the purpose of efficient utilization of water and fertilizer.Therefore,1.0 m water head and 400mg/L fertilization concentration were more suitable for the growth of pakchoi in greenhouse.From the greenhouse planting experiment,it can be seen that vegetables with different growth cycles have different demands on water and fertilizer supply,and the changes of pressure water head,fertilization concentration and other parameters are closely related to the vegetable growth.Soil box experiment was carried out to simulate the distribution and migration of soil water and nitrogen under the condition of moistube irrigation and fertilization.Five pressure water heads of 1.0 m,1.25 m,1.5 m,1.75 m and 2.0 m were set in the experiment.The buried depth of moistube was 20 cm.Analytical pure urea was dissolved in irrigation water,and the concentration of fertilizer solution was set at 400 mg/L.Under the same fertilization concentration and the same infiltration period,the soil water content,measured the content of ammonium and nitrate nitrogen,the shape and migration distance of wetting front,the cumulative infiltration amount and other indexes,explored the distribution and migration of soil water and nitrogen under pressure head.The results showed that the soil water content and cumulative infiltration increased with time,and the higher the pressure head,the faster the growth rate and the greater the value at the end of the test.The profile of soil wetting body is an approximate ellipse with a small upper part and a large lower part centered on the moistube.The migration distance of the wetting front in each direction can be fitted into the form of a power function,Y=a T~b.Under the action of gravity,the migration distance of wet front in vertical downward direction is the largest.With the infiltration of fertilizer,the growth rate of ammonium and nitrate nitrogen content in soil slowed down from the fast rate.With the increase of pressure head,the nitrogen content in the same position increased.The longer the distance from the moistube,the lower the soil nitrogen content,ammonium nitrogen enrichment in-10～10cm soil layer,which ammonium nitrogen content get higher when the pressure head get greater.Nitrate nitrogen in the soil was transported with water,showed the similar distribution rules to water.The higher the pressure head,the more uniform the distribution of nitrate in the soil.