Affecting Factors About Clogging Of Irrigation Emitter And Fertilizer Efficiency Under Fertigation In Shiyang River Basin

Drip irrigation with fertigation has the advantages of water conservation,increasing the utilization rate of fertilizer and improving the yield and quality of crops.It's widely used in Shiyang river basin where is arid.Due to the price of specific fertilizer for drip irrigation is high,field application are mostly used general fertilizer.It's easy to cause the drip irrigation emitter clogging,which resulted in the reduction fertigation uniformity,so the drip-tape with thin wall which made by recovered drip-tape is widely used in places such as Gansu,Xinjiang.This drip-tape's price is low and can be replaced every year which avoid reduction of irrigation uniformity caused by clogging.The pressure of drip-tape with thin wall cannot be too high,under the condition of low pressure water irrigation uniformity and anti-clogging performance will be lower,replacement of drip-tape also cannot solve the problem of emitter cogging,so it is necessary to research the affecting factors about clogging of emitter and fertilizer efficiency under fertigation to improve the evenness of fertigation.This paper selects the drip-tape with flanking labyrinth channels and drip-tape with plastic flake,which is widely used in Xinjiang and Gansu province,and conducts hydraulic performance and anti-clogging performance test and numerical simulation analysis respectively.Through the observation of clogging of drip-tape,clogging matter and the soil moisture content,soil nutrient content and crop yield to explore the influence factors about clogging of drip-tape and fertilization uniformity.The main conclusions are as follows.(1)Based on the study of the hydraulic performance of the four drip-tape,it is concluded that all of them can meet the requirements of irrigation quality,the drip-tape with plastic flake has the highest irrigation uniformity coefficient,which is basically maintained at 98%,while the three drip-tape with flanking labyrinth channels are maintained at more than 94%.In the range of laying distance from 0 to 48 m,the water head loss along drip-tape with plastic flake is not significantly affected by the distance,while the irrigation uniformity of the drip-tape with flanking labyrinth channels is lower than the former.However,when the laying length is less than 30 m,it's water head loss of is less than the former.(2)The results show that the uniformity of the drip-tape with ohm-chain is greater than the others.With the increase of irrigation times,the 1# drip-tape clogged from back end gradually extend to the upstream and the 2# drip-tape clogged from forepart and back end extend to the midstream.In the intermittent irrigation experiment,drip-tape with plastic flake prone to clogging under the pressure below 0.09 MPa,need to set up 120 mesh disc filter.With increase of laying length the clogging of drip-tape with flanking labyrinth channels is aggravating and this type drip-tape has the best effect on fertigation with the pressure of 0.05 MPa for long-distance(48m),and the best pressure is 0.04 MPa when the length of drip-tape is less than 30 meters.Through the observation of clogging matter in drip-tape,found that the process of clogging has both physical and chemical,the matter including the water mixed soil impurities such as small gravel and insoluble matter generated by the silicate in soils and phosphate in phosphatic fertilizer chemical reaction and calcium ions in water and phosphate ions in fertilizer precipitation reaction.The clogging of drip irrigation with drip head mostly occurs at the entrance and the front part of the labyrinth channel,which is more likely to occur when the with flow is small making it difficult for subsequent fertilizers to pass through.(3)By using the FLUENT software modeling four kinds of labyrinth channels to numerical analysis their hydraulic performance,it is concluded that the pressure is uniform decline from entrance along internal flow direction in the labyrinth channel,internal water pressure changes occurred in the turning angle of the channel.The energy dissipation ability of labyrinth unit is negatively correlated with length of channel.The regularity of flow field changes in each labyrinth unit is basically the same,and there are obvious vortices and secondary flow areas at the back water corner of the ohmic chain and circular arc flow types of labyrinth channels,which can effectively alleviate the clogging.(4)According to study on the soil moisture content,soil nutrient and crop yield,it is concluded that the fertilizer uniformity irrigated by drip-tape with plastic flake which use high pressure is higher than drip-tape with flanking labyrinth channel,and the better pressures for the former are 0.09 and 0.1 MPa and for the latter is 0.06 MPa.When setting drip-tape with flanking labyrinth channel under lower pressure,the crop yield is higher than setting drip-tape with plastic flake under higher pressure,which indicate that that lower pressure drip irrigation can improve the rate of seedling preservation and increase the corn yield.