Effects Of Salt Water Drip Irrigation On Soil Salinity And Haloxylon Ammodendron Growth

Due to the special geographical location and climatic conditions,the southern margin of Junggar Basin is short of water resources and the ecological environment is extremely fragile.Haloxylon ammodendron,as a typical desert plant in the region,has good functions of sand fixation and ecological conservation.The proportion of agricultural water in the middle and upper reaches of the southern margin of Junggar basin is too large,so it is difficult to guarantee the ecological water resources in the lower reaches.Therefore,the development and utilization of local saline water resources to irrigate desert plants provides a new way for ecological environment construction.In this experiment,the typical desert plant Haloxylon ammodendron was selected as the research object,and the pit test was carried out in the Key Laboratory of Modern Water-saving Irrigation Corps.Five irrigation salinity levels were set as A:1 g L^-1,B:6 g L^-1,C:9 g L^-1,D:12 g L^-1,E:15 g L^-1.The effects of drip irrigation with different mineralized water sources on soil water content,soil salt content,ion distribution and soil hydrochemical types of Haloxylon ammodendron were studied.The contents of chlorophyll,proline,malondialdehyde,soluble protein and soluble sugar,plant height,branch length,stem diameter and crown width of Haloxylon ammodendron were determined.Based on the above,the main conclusions are as follows:(1)The difference of soil water content in different infiltration time is obvious.24 hours after drip irrigation,the influence of salinity concentration on soil water content was 6>9>12>15>1 g/L.In the first year of the experiment,the soil water content of 6 g/L treatment was the highest at 60 cm,and the highest at 80 cm in the second year.The closer it is to the emitter,the higher the soil water content.and the advancing distance of horizontal wetting front of 1?9?12 g/L and 15 g/L treatment was greater than that of vertical wetting front,while that of 6 g/L treatment was on the contrary,while the effect of salinity on soil water content was 15>12>9>1>6 g/L.In the first year of the experiment,the soil water content of treatment6 g/L was the lowest at 60 cm and the lowest at 80 cm in the second year.The farther away from the horizontal direction,the lower the soil water content,and the lowest soil water content was 0.89-1.16%at r=30 cm and z=20 cm.(2)The effect of different salinity on soil salt content is 15>12>9>6>1 g/L.The salt content of 20 cm in the surface layer of soil was the highest,and the cumulative amount was 3.24 g kg^-1.Compared with the first year,the salt content in the second year increased by 0.29,0.56,0.74,0.76 and 1.04 g kg^-1.24 hours after irrigation,the soil salt content increased in turn with the increase of soil depth,and the soil salt accumulated under the emitter and advanced vertically and horizontally.At 20 days after irrigation,the soil salt content decreased with the increase of soil depth.With the minimum at r=0 cm,z=100 cm and the highest at r=30 cm,z=20 cm,and there was no significant difference between two years(P<0.05).(3)The effect of different salinity irrigation on ion content was SO₄^2->Cl^->Na⁺>Ca²⁺>Mg²⁺>HCO₃^->K⁺,and the contents of Na⁺,SO₄^2-,Cl^-and Ca²⁺increased significantly with salinity.There was a significant correlation with salinity(P<0.05),but there was no correlation between HCO₃^-and K⁺(P>0.05).The contents of SO₄^2-,Cl^-and Na⁺ions in soil under salt water drip irrigation changed significantly with the increase of salinity.The cations of soil aqueous solution gradually changed from Ca²⁺to Na⁺,and the anions gradually changed from SO₄^2-to Cl^-.In the first year,the hydrochemical type gradually evolved from SO₄^2-·Ca²⁺·Mg²⁺type to SO₄^2-·Cl^--Na⁺type,and in the second year,the hydrochemical type gradually changed from SO₄^2-·HCO₃^--Ca²⁺·K⁺to SO₄^2-·Cl^--Ca²⁺·Na⁺.(4)The physiological effects of different salinity treatments on Haloxylon ammodendron showed that the contents of proline,malondialdehyde and soluble sugar increased with the increase of salinity,and there was a significant positive correlation(P<0.05),and with the increase of irrigation time,the contents of soluble sugar and chlorophyll reached the maximum at the middle stage,with an average of 0.63 mg/g and23%and then decreased.There were significant differences in tree height,branch length,stem diameter and crown width under different salt treatments(P<0.05).The effect of salinity on growth was 6>1>9>12>15g/L.under 6 g/L treatment,Haloxylon ammodendron plant height increased by 51.48%,stem diameter increased by 36.41%,branch length increased by 42.90%,and crown width increased by 67.99%.Through the comprehensive evaluation and analysis of different mineralization degree on the physiological growth index of Haloxylon ammodendron by different grey correlation methods,it is concluded that the treatment with mineralization degree of 6 g/L can be used as the concentration of irrigation Haloxylon ammodendron.