Effect Of Nitrogen And Phosphorus Combined With Water And Fertilizer Integrated Mode On The Clogging Process Of Emitter And Tomato Growth In Saline Water Drip Irrigation

Saline water irrigation is an important mean to alleviate the water crisis in the world.Drip irrigation is considered to be the most suitable way of saline water irrigation because it can realize the precise regulation of water,fertilizer and salt under the condition of saline water irrigation.However,the amount and variety of ions in the saline water will lead to the formation of blocking substances in the emitter channel,which will affect the safety of the system.In recent years,the process of integration of water and fertilizer is speeding up day by day.The application of fertilizer under the condition of saline water drip irrigation may further aggravate the risk of emitter clogging.Therefore,it has important theoretical significance and practical guiding value to study the mechanism of irrigator blocking,prevention measures and the influence of different prevention measures on soil crop system under the condition of drip irrigation and fertilization of saline water.In this paper,indoor experiments were conducted to explore the mechanism and prevention measures of clogging of emitters in drip irrigation and fertilization system with saline water.In the test,the types of emitters,water quality and application mode of phosphate fertilizer are considered.By measuring the flow rate of emitters regularly and the clogging substances in the emitters after the test,the influence of various test factors on the formation process of clogging substances and the clogging mechanism is analyzed.In order to evaluate the effect of clogging prevention measures on soil environment and crop growth,tomato was taken as the research object.The experiment was carried out considering the application mode of phosphate fertilizer and the layout of drip irrigation belt.The dynamic distribution of soil moisture content,soil nitrogen and phosphorus was monitored.The plant height and leaf area index(LAI)were measured regularly,and the yield was also measured.The effects of different application modes of phosphate fertilizer on the distribution of soil nitrate nitrogen and available phosphorus and the physiological growth indexes of tomato were analyzed.The main conclusions are as follows:(1)under the condition of phosphate fertilizer alone,the water-soluble acid urea phosphate has good anti blocking performance,and the water-soluble weak alkaline diammonium phosphate accelerates blocking.With the increase of the conductivity of water and electricity,the clogging speed of each phosphate fertilizer treatment is accelerated,and the increase of diammonium phosphate treatment is larger,followed by the control of groundwater and monoammonium phosphate treatment,and the emitter of urea phosphate treatment always shows good anti blocking performance.(2)When the conductivity of irrigation water is more than 4 dS/m,the rapid clogging of drip irrigation system will be caused by the application of nitrogen and phosphorus fertilizer,and the deposition of phosphates in the clogging material is more than 85%.Under the condition of groundwater and saline water with conductivity of 2 dS/m,the clogging rate of emitter is relatively slow when monoammonium phosphate and urea or ammonium phosphate are mixed for fertilization.The use of weak acid nitrogen phosphate fertilizer solution is an effective measure to slow down the clogging of emitter in the process of water fertilizer integration.(3)Under the condition of different ratio of acid phosphate fertilizer and nitrogen phosphate fertilizer,With the increase of electrical conductivity,the blocking speed of each fertilizer treatment was accelerated,and the clogging range was positively related to the pH of fertilizer solution.When the conductivity increased to 4dS/m,except for the treatment of U3(Urea+UP),which was the most acidic fertilizer solution,the other fertilizer treatment emitters were clogged rapidly.By adjusting the proportion of urea phosphate to make the fertilizer liquid acid,the prevention measures are feasible,and the target pH value should be negatively related to the conductivity of irrigation water.It is suggested that the target pH values are 4.0 and no less than 3.0 when the water quality is 2 dS/m and 4 dS/m respectively.(4)Under the condition of applying phosphorus fertilizer to the Saline water drip irrigation,the clogging of the emitter is mainly chemical clogging,and phosphate is the main component of the clogging material.(5)The application of acid phosphate fertilizer and nitrogen fertilizer can improve the soil available phosphorus content,the leaf area index of tomato and the crop yield.The yield of monoammonium phosphate treatment is 9%higher than that of conventional phosphate fertilizer treatment.From the aspect of soil-crop environment,the application of acid phosphate fertilizer is a feasible measure to prevent the clogging of drip irrigation emitters.To sum up,under the condition of application of Saline water and phosphate fertilizer,the ion environment of the fertilizer solution is complex after the mixture of Saline water and fertilizer.The main reason for the clogging of irrigators is chemical clogging.It is an effective method to control the clogging of irrigators by applying urea phosphate to regulate the pH value of the fertilizer solution.