Soil Salinization Variability And Its Relationship With Crop Types In Hetao Irrigation District Of Ningxia

Hetao Irrigation Area in Ningxia Region is an important commodity grain base in China.Soil salinization has always been one of the important factors restricting the agricultural development of this area.Its soil salinity and pH have spatial heterogeneity and vertical heterogeneity under the influence of natural conditions and human disturbance.Sexuality,research on soil salinity and pH variation characteristics can provide decision-making reference for rational development and utilization of land and soil salinization prevention and control.Farmland water and salt conditions will affect crop growth,indirectly affect crop distribution,and different crop irrigation and drainage methods.Different farming methods,such as cropping measures and crops,can affect the movement of salt in vertical and horizontal directions,study the relationship between soil salinity and pH variation characteristics and crops,and optimize the planting system and formulate appropriate Irrigation measures and improvement measures to control soil salinization and achieve efficient use of water have important scientific and practical significance.In this paper,the typical irrigation area of Hetao in Ningxia was selected as the research area to study the variation characteristics of soil salinity and pH in spatial and vertical directions.The remote sensing technology was used to extract crop types.Based on the salinity and pH data of the study area and the distribution of crops,the differences of changes in soil salinity and pH after different crop planting were analyzed.The research results are as follows:(1)The degree of salinization in the whole study area is serious.The soluble salt ions are mainly magnesium ion,sodium ion,chloride ion and sulfate ion.The carbonate ion and pH value increase with the depth of the soil layer.The ions gradually decreased with the increase of soil depth,the total salt of the surface layer was strong variability,the whole salt of other layers was moderately variable intensity,and the PH value was weak variation intensity.PH and carbonate have a strong positive correlation.Affected by the spring salt return period,all salts and all ions except carbonate and bicarbonate have different degrees of surface aggregation.The spatial distribution of total salt,salt ion and PH is generally high in the northwest and southeast.The low characteristics are affected by topographic factors.The content of total salt,chloride ion,sodium ion and calcium ion in the transition zone of the surface alluvial plain of the Yellow River and the alluvial plain of Helan Mountain is low.The salt profile type shows in this spatial distribution range.Average type and bottom type.(2)Using GF1-WFV time series data with better time resolution and spatial resolution,combined with different vegetation fertility characteristics,the decision tree based on the characteristics of main crop curves is more accurate.The rice is mainly distributed in the northern part of the Helanshan piedmont alluvial plain and the alluvial plain of the Yellow River.It is basically contiguous.The corn and wheat are distributed in the transition zone of the alluvial plain of the Helan Mountains and the alluvial plain of the Yellow River.The alfalfa is mainly distributed in the area south of the Shahu Lake.(3)The total salt,sodium and chloride ions in the surface of rice are significantly higher than other crops.The content of sulfate ion and magnesium ion is slightly higher than other crops.The rice is mainly distributed in the area where the salt profile type is epimerized,while corn and wheat.It is mainly distributed in the area where the salt profile type is average.Compared with corn and wheat,rice is mainly distributed in areas where salinization of surface soil in spring is more serious.It indicates that the spatial variation and vertical variation of soil salinity affect the spatial distribution of crops to some extent.(4)Planting different crops will have certain influence on the variation characteristics of soil salinity and pH value.The characteristics of total salt,pH value and ion change before and after planting are different.The total salt content of rice is much lower than that of corn after planting rice.And wheat,the pH increase is less than corn and wheat,and the reason is analyzed.On the one hand,it may be due to the fact that as the rice grows,some of the acidic substances in the root exudates cause the soil pH to decrease and inhibit the precipitation of magnesium ions.On the other hand,the rice irrigation method is flood irrigation,which will drain regularly.Compared with corn and wheat,it can take more salt.