Water And Salt Regulation In Typical Farmland Of The Yellow River Delta Based On Water Balance

Saline alkali land is an important reserve land resource.The Yellow River Delta is one of the regions with the fastest natural growth of land area in the world.The area of saline alkali land is large and widely distributed,and the degree of farmland salinization is heavy.With the rapid development of social economy,the population has increased rapidly and the area of cultivated land has decreased continuously.In order to ensure national food security,it is imperative to develop and utilize saline alkali wasteland and improve salinized farmland.The large-scale improvement and utilization of saline soil can not be separated from the rational allocation of water resources.The temporal and spatial distribution of precipitation in the Yellow River Delta is uneven,and the groundwater is buried in a shallow depth and highly mineralized,which is difficult to use.The supply of fresh water resources mainly depends on the passenger water of the Yellow River.More than 80% of the total water supply in the region is used for agriculture,while the ecological environment uses very little water.The natural instability of the ecosystem in the Yellow River Delta and the unreasonable development of human beings lead to the degradation of the ecological environment in the region,which is very difficult to restore and the process is slow.The squeeze of agricultural water on the proportion of ecological water will further aggravate the degradation of the ecosystem.Therefore,how to reasonably allocate and utilize the limited water resources,further reduce the proportion of agricultural water and optimize the allocation pattern of water resources on the premise of ensuring saline soil improvement and agricultural sustainability,is of great significance to the ecological protection and high-quality development of the Yellow River Delta.Taking Dongying City,Shandong Province as an example,based on the analysis of the characteristics of water and soil resources in the Yellow River Delta,this paper studies the physical and chemical properties of soil and water in the typical test area.On the basis of calculating the irrigation water demand of main crops in the test area,the paper analyzes the supply-demand balance of farmland irrigation water,and puts forward countermeasures and suggestions for regulating salt through water management.The main conclusions are as follows:(1)Based on the data and statistical analysis of water and soil resources in Dongying City in recent 20 years,this paper explores the composition and utilization status of water and soil resources,spatial and temporal change characteristics and spatial matching pattern.It is found that Dongying City is relatively rich in land resources,but water resources are very scarce.The water supply structure is single,and the degree of water and soil matching generally presents a pattern of "high in the southwest and low in the northeast",with Guangrao County being the highest(40000m3/hm2),Kenli district is the lowest(400 m3/hm2).(2)Through field sampling and indoor analysis,the physical and chemical properties of the soil and water in the typical test area were determined.The path coefficient method was used to analyze the correlation of the chemical parameters of the soil extract(Cl-,SO42-,Na+,K+,Ca2+,Mg2+,SAR,p H and EC5:1).At the same time,the irrigation water quality of the water in the test area was evaluated.It was found that the soil texture in the typical test area was mainly silty loam,which was compared with the reclamation area,Guangrao County has more sand particles in the upper layer and clay particles in the lower layer of soil,large groundwater depth,low salinity and light soil salinization,which is more suitable for the development of agriculture.(3)Using Hargreaves-Samani method and crop coefficient method to calculate the water demand of main crops in the test area,and then according to the calculation of crop leaching water demand and effective precipitation during the growth period,the irrigation water demand of main crops in the test area is obtained,from large to small,as follows: Winter Wheat > Spring Potato > rice > cotton > spring maize > beans > summer potato > sorghum >Oil > millet > summer maize,with a range of 0.62~706.01m3/mu;Based on the analysis of supply and demand balance of actual farmland water consumption,it is found that the total water demand of main crops in the experimental area can not be met under the condition of full irrigation;The Regulation Countermeasures of deficit irrigation and unconventional water utilization are put forward.Under the condition of deficit irrigation,the maximum irrigation water demand in the experimental area only occupies 27.66% and 59.77% of the water.Diluting the unconventional water source with EC < 2.5 m S/cm can save more than 65% of fresh water;It is suggested that according to the characteristics of salt and drought tolerance of crops,crop planting structure should be adjusted and the gradient of sequential utilization of irrigation water should be established.For Guangrao County,where the soil salinization degree is relatively low,it is suggested to vigorously develop modern and efficient agriculture and rationally allocate water resources for salinized farmland improvement.For reclamation areas with large unused saline alkali land and difficult development,it is suggested to use unconventional water sources for halophyte planting to give full play to their ecological wetland function.