Effects Of Brackish Water Drip Irrigation On Soil Environment And Grape Quality

The soil in the Yellow River Delta belongs to coastal saline-alkali soil,which is a shallowsea sediment formed by long-term combined action of River handling and sea water crest support.The salinization is severe and the groundwater level in the region is high.The groundwater salinity is high due to the influence of sea water salinity and evaporation.In the improvement of traditional saline-alkali land,the method of "water pressure and salt" is often used,i.e.washing soil salinity by flooding,but this extensive irrigation method consumes a large amount of water,which is incompatible with the current situation of relative shortage of local freshwater resources.A large number of studies have shown that brackish water can also rinse soil salinity.The Yellow River Delta is rich in brackish water resources,which is easy to exploit and has a great prospect for development and utilization.In this study,the influence of brackish water irrigation on soil water and salt transport,grape rhizosphere soil environment and fruit quality was studied by combining field test with indoor simulated infiltration test,and by setting alternative irrigation methods of brackish water with different mineralization and brackish water.(1)Drip irrigation with brackish water mainly affects the distribution of water and salt in upper soil layer;brackish water with low mineralization can reduce soil salinity to a certain extent,but brackish water with low mineralization can also cause soil salt accumulation with the increase of irrigation times with brackish water;with the increase of mineralization of brackish water,the degree of soil salt accumulation increases accordingly;the combination of irrigation with brackish water first and then brackish water can reduce the degree of soil salt accumulation.(2)Under the infiltration of brackish water,the soil infiltration performance first increases and then decreases with the increase of brackish water mineralization,reaching the highest when the mineralization is 3 g/L;when the soil moisture is not saturated,the infiltration rate decreases with the infiltration time;the depth of soil desalination decreases linearly with the mineralization of brackish water;for soils with higher initial salinity,brackish water It can also play a leaching role,which decreases with the increase of salinity of brackish water.(3)The cumulative infiltration has a significant influence on the leaching effect of soil salinity.The larger the cumulative infiltration,the more adequate the leaching is;the leaching efficiency and cumulative infiltration have a power function decreasing trend;the leaching effect of brackish water on soil salinity decreases with the increase of soil depth;the leaching effect of brackish water on upper soil is greater than that on lower soil,and the difference decreases with the increase of the amount of leaching water..(4)Under the alternate infiltration of saltwater and fresh water,the quality of irrigation first affects the distribution of salinity in deep soil,then the quality of irrigation affects the distribution of salinity in upper soil;the infiltration mode of light and salt first increases the content of salinity in upper soil;the infiltration mode of first salt and then light decreases the content of salinity in upper soil,and the salinity in upper soil is close to that of fresh water;the leaching effect of two infiltration modes on the overall soil salinity.There is no significant difference,the difference is limited to the distribution of salt in the soil.(5)The activity of soil enzymes and the number of microorganisms were negatively correlated with the mineralization degree of brackish water,and the activity of soil enzymes was positively correlated with the number of microorganisms;the activity of soil enzymes and the number of microorganisms were significantly affected by brackish water drip irrigation in the short term;the mineralization degree of brackish water had no significant influence on the activity of soil enzymes and the number of microorganisms;the alternating irrigation of brackish and fresh water had no significant effect on soil enzyme activity and microbial quantity;brackish water with low mineralization had no significant effect on soil enzyme activity and microbial quantity(P>0.05).Soil enzyme activities and microbial population were significantly decreased by medium and high salinity brackish water irrigation(P<0.05),soil enzyme activities were decreased by 3.24%～19.72%,and microbial population was decreased by 12.99%～45.77%.(6)The alternating irrigation sequence of brackish and fresh water and the mineralization degree of brackish water will affect the quality of fruit.The quality of early stage irrigation water had a significant effect on fruit quality,while that of late stage irrigation water had no significant effect on fruit quality;(salt-light-salt 2 g/L)treatment had no significant change on fruit quality;(salt-salt-light 2 g/L)treatment increased soluble sugar content by 2.14% and sugar-acid ratio by 5.2%;5 g/L brackish water significantly reduced fruit quality(P<0.05);(salt-salt-light 3.5 g/L)The soluble sugar content and the sugar-acid ratio of the fruit were reduced by 5.99% and 5.55% respectively,which reduced the quality of the fruit.The soluble sugar content and the sugar-acid ratio of the fruit were increased by 11.71% and 34.94%respectively under salt-light-salt 3.5 g/L treatment,and the fruit quality was the highest.In agricultural production application,5 g/L brackish water will cause soil salt accumulation,reduce soil fertility and reduce fruit quality,so it should be avoided as far as possible;2 g/L brackish water will not cause serious soil salt accumulation or reduce fruit quality,but fresh water consumption is relatively large and is not recommended.3.5 g/L brackish water with "salt-light-salt" alternative irrigation method has the highest fruit quality.Although it will cause a certain degree of soil salt accumulation in a short time,the annual dynamic balance of salt can be achieved by irrigation and precipitation in the next year,which can be considered for use.