Study On Improvement Effect Of Coastal Saline Soil

In recent years,the urbanization process in the coastal area has been accelerated,the population has been increasing rapidly,the land resources have been occupied in large quantities,the contradiction between human and land has been aggravated,and the soil salinization has become an important factor limiting the development of the coastal area.In order to maintain sustainable and rapid economic development in the coastal area,it is necessary to rationally control and improve the saline-alkali land.This paper,taking typical coastal saline-alkali land in Caofeidian of Hebei province as the study area,using the method of space instead of time,with unimproved saline-alkali wasteland as the control CK,selected the coastal saline-alkali land improved by three modes which were"NO covering-60cm improver-tree mode"(T1),"Covering-60cm improver-shrub mode"(T2),"Covering-40cm improver-herbaceous mode"(T3)as the research object,investigated the surface plants and soil in the land improved under three modes with different years,analyzed the distribution characteristics of soil water and salt under different improvement modes,studied the changes of plants growth and soil physical and chemical properties with years of improvement under different improvement modes,and discussed the dynamic change of improvement effect of different improvement modes in coastal saline-alkali land.The main conclusions are as follows:(1)After one year of salinized soil improvement,the spatial vertical distribution characteristics of soil water content and salt content in the three modes all showed an increasing trend with the increase of depth,and the salt content accumulated to the deep soil with the increase of water.Compared with the saline-alkali wasteland,the influence of rainfall on soil water content in the three improvement modes was greater,and the variation coefficient of soil water content was significantly larger,which indicated that the soil permeability was better and the soil water content changed sharply in the three improvement modes.The monthly dynamic change trend of soil salt content and water content of the three modes were basically the same.Except for the 40-60cm soil salt content of T3,the soil salt content remained below 0.4%,which was reduced by more than 85%compared with CK,and the monthly change range was small,indicating that the desalination effect of the three modes improved for one year was good.(2)The three modes could significantly improve soil physical and chemical properties,reduce soil bulk density,salt content and SAR,and increase soil nutrients.The improved plants grew well,and the improved effect could be maintained for a long time.The plant height,ground diameter and tiller number increased with the increase of improvement years,and the survival rate was above 95%.Total soil porosity was significantly increased,and soil salt content in all the improvement years of the three modes was reduced by more than 80%,and the effect of salinity reduction in the 0-20cm soil layer was the most obvious,and the salinity in all the years of the T1,T2 and T3 modes was maintained below 0.31%,0.37%and 0.32%,respectively.The overall improvement effect of T3 mode on soil physical and chemical properties was the best,especially in shallow soil.The soil salt content,water-soluble cation content and SAR of T3 mode were lower than those of T1 and T2 modes.(3)After the improvement of the three modes,soil nutrients showed obvious surface aggregation,and the contents of available nitrogen,available phosphorus and organic matter decreased with the increase of soil depth.Compared with the saline-alkali wasteland,the nutrient content of the three modes increased significantly,and the content of available nitrogen of the three modes increased by more than 1 time in all the years.With the increase of the improvement years,the contents of available nitrogen,available phosphorus and organic matter in the soil of the three modes all increased firstly and then decreased,and reached the highest in 5 years.The content of alkali-hydrolyzed nitrogen in the 0-20cm soil layer of the T2 mode increased by 3.88 times.After 11 years of improvement,the organic matter content in the 20-40cm and 40-60cm soil layers of T2 and T3 modes was close to or even lower than that in the saline-alkali wasteland,and the soil nutrients could be guaranteed by increasing the application of organic fertilizer.(4)After the improvement of the three modes,there were significant correlations among some indexes of soil physical and chemical properties,among which,salt content was positively correlated with bulk density,SAR and available potassium,and negatively correlated with organic matter and porosity,indicating that decreasing soil bulk density and SAR and increasing porosity and organic matter content could promote the decrease of soil salt content.In conclusion,this article preliminary expounds the coastal saline land comprehensive improvement of soil water and salt movement rule,studies dynamic change of improvement effect of coastal saline land with different improvement mode,enriches improvement mode of the coastal saline land,which provides scientific basis for the further study of soil water and salt movement rules in the coastal saline-alkali land and the reference for the selection and improvement of the amelioration in coastal saline land.