Soil Water And Nitrogen Transport And Greenhouse Vegetables Growth Under Moistube Irrigation And Fertilization

Moistube irrigation technology is an emerging water-saving irrigation technology developed rapidly in recent years.Compared with drip irrigation,the water-saving effect is better.Moistube irrigation is a new type of polymer material with nanoscale voids of the outlet pipe as an emitter,which has been widely concerned by scholars at home and abroad since 2010.The principle of micro-wetting irrigation is the principle of semi-permeable membrane penetration.Through the dynamic action of the water potential difference between the inside and outside of the membrane and the potential of the soil matrix,the water is seeped out from the semi-permeable membrane and the outflow speed is slow.It is a water-saving irrigation technology that can supply water to the root area of crops automatically and in real time.Based on the basic principle and characteristics of moistube irrigation,this paper proposed the integration of water and fertilizer for moistube irrigation,carried out indoor simulation test and vegetable planting test of two facilities,and set two pressure water head treatments h= 100 cm,150cm and three nitrogen(urea)levels 0mg/L,500mg/L and 1000mg/L for a total of 6 treatments.In this paper,the flow out of micro-moist pipe under different pressure heads and at different nitrogen application levels,the movement of wetting front and the distribution of soil water,as well as the distribution of nitrate nitrogen and ammonium nitrogen in soil were investigated,and the combination of pressure head and fertilization concentration suitable for increasing crop yield in micro-moist irrigation and fertilizer integrated planting was selected.This experiment mainly draws the following conclusions:1.In the indoor soil box simulation test,it was found that the pressure water head and the concentration of urea fertilizer liquid had influences on the cumulative infiltration amount,moisture front migration,soil water distribution,and the contents of ammonium nitrogen and nitrate nitrogen in the soil.At the same time,at the same concentration of the infiltration fluid,the pressure head increases and the cumulative infiltration amount increases.The farther the wetting front migrates,the higher the soil moisture content near the wetting pipe is.When the pressure head is the same,the concentration of the infiltration solution increases,the cumulative infiltration amount decreases,the distance ofthe wetting front is smaller,and the soil moisture content near the wetting pipe is relatively small.The migration distance of each direction of the wetting front is greater than that of the horizontal direction and the vertical direction.The migration of the wetting front shows a power function relationship with the passage of time,and the advance rate of the wetting front slows down with the extension of time.The pressure head and the concentration of urea fertilizer had significant effects on the content of ammonium nitrogen and nitrate nitrogen in soil.The concentration of pressure head and urea fertilizer increased,and the content of ammonium nitrogen in soil increased.The content of ammonium nitrogen in the soil of each treatment increased gradually and reached the peak after infiltration for a period of time,and the content of ammonium nitrogen tended to decrease after the peak.Different treatments took different time to reach the peak of ammonium nitrogen content.Water infiltration at 100 cm and 150 cm pressure reached the peak of ammonium nitrogen content on the third day.However,under the infiltration of fertilizer solution,insufficient water in the soil or too large urea concentration would affect the hydrolysis of urea,and the time required for ammonium nitrogen content to reach the peak was prolonged.The nitrate nitrogen content in soil increased with the increase of pressure head and fertilization concentration,and the nitrate nitrogen content decreased with the increase of the distance from the micro-moist pipe belt,while the nitrate nitrogen content in soil increased with the extension of infiltration time.The distribution of ammonium nitrogen in the soil was more uniform when the water was permeated,but the nitrate nitrogen accumulated near the wetting front.2.In the vegetable planting experiment of outdoor facilities,the pressure head had a greater influence on soil water distribution 0～13 days after sowing,and the mass moisture content of 150 cm pressure head was higher than that of100 cm pressure head.Plant height and stem diameter treated with different pressure water head and nitrogen concentration showed "S" type tendency.Different pressure head had significant effect on stem diameter,but different nitrogen concentration had no significant effect on stem diameter.When the pressure head was 150 cm and the fertilizer application rate was 1000 mg/L,it was more conducive to plant growth.Under this treatment,fresh weight was maximized,yield was maximized and nitrogen agronomic efficiency wasmaximized.Nitrogen application can increase SPAD value of leaves and dry matter accumulation.Water convolvulus SPAD values in the early stages of the maximum,and then gradually decreases,and the top 1 leaf(L1)to pressure head and the change of the concentration of n is sensitive,increasing the pressure head and applying nitrogen fertilizer make water convolvulus top 1 leaf(L1)about 22 days to planting SPAD values have rebounded,improving photosynthesis rate,increase dry matter accumulation,under the same pressure head,nitrogen concentration of 1000 mg/L ` dry matter accumulation was obviously higher than 500 mg/L.In the integrated system of water and fertilizer irrigation,In the process of continuous planting of Chinese cabbage,different treatments of water spinach fertilization would have different effects on the content of nitrogen in the soil.Excessive ammonium nitrogen content in the soil or large amount of irrigation water would inhibit the growth and development of crops,resulting in reduced production.In the 1 m pressure head treatment group,the plant height,stem diameter,yield,irrigation water productivity and nitrogen agronomy efficiency of the cabbage were all increased with the increase of nitrogen application concentration.The fertilization treatment with 1 m pressure head and 1000mg/L can obtain a large nitrogen agronomic efficiency,and the yield and irrigation water productivity are the highest.The fertilization treatment with 1.5m pressure head and 500 mg/L can obtain larger yield and irrigation water productivity,and the nitrogen agronomy efficiency is the highest.