| Soil salinization is an important factor that restricts agricultural development.China is one of the countries with serious soil salinization in the world.And the low plain area around Bohai is a typical coastal salinization area in China.It is also an important agricultural production base.However,the environment and basic conditions of salinized farmland are poor and the spatial variability of soil properties is large,which increases the difficulty of farmland management and restricts the development of agricultural production.The waste of resources and the pollution of the ecological environment are also caused by over-fertilization and over-irrigation.Therefore,the spatial variability of soil water,nutrient and salt in salinized farmland should be analyzed and controlled by district management.And it is an important way to alleviate the contradiction between input and output,agriculture and environment,enhance productivity of saline soil and save cost and efficiency.In this paper,the salinized farmland in Wudi County is taken as an example.Soil water,nutrient and salt data are obtained through field survey and sampling analysis.Under the support of GIS,SPSS,MATLAB and other software,the spatial variation characteristics of the soil water,nutrient and salt in the county farmland are analyzed by using the classical statistics and geo-statistics methods,and the fuzzy mean clustering method is used to divide the farmland management zoning.Based on the zoning results,combined with the water-salt integrated control model and nutrient balance regulation model,the control scheme of water,nutrient and salt zoning is on research.The main results are as follows:(1)Under the support of SPSS20.0,the descriptive statistical characteristics of soil nutrient and salt were studied by using the classical statistical method.It was found that the salt content and pH value of farmland soil in Wudi County were high,and the soil salinization level was mainly in the moderate-severe level.And the variation coefficient of organic matter,available nitrogen,available phosphorus,available potassium and salt content in the soil is between 25% and 91.6%,all of which are of medium variability.The management partition and zoning regulation should be carried out.(2)Based on the geo-statistics method of ArcGIS 10.2,the optimal semi variance function model of soil nutrient and salinization was determined by spatial trend analysis and cross validation.The spatial distribution of soil nutrient and salinity was analyzed by Kriging interpolation,and its spatial structure was analyzed according to the semi-variogram model and its parameters.The results showed that,in May 2016,the soil organic matter,available nitrogen and available phosphorus in Wudi County had medium spatial variability,and the available potassium,salt content and pH had strong spatial variability.In September 2016,the soil organic matter and pH had weak spatial variability,and the available nitrogen,available phosphorus and available potassium had medium spatial variability,and the salt content of the soil had a strong spatial variability.(3)Based on the fuzzy c-means algorithm(FCM),the membership degree of each sample point is calculated in the MATLAB R2016 a,and the area is divided according to the maximum membership degree principle in MAPGIS 67.The farmland of the whole county in May and September 2016 is divided respectively into 3 and 4 management partitions.According to the soil property value and the membership degree matrix of each sampling point,the interpolation analysis is carried out by the geo-statistics method in ArcGIS 10.2,and the management partition inspection and precision check are carried out by the descriptive statistical analysis and the least significant range method(LSR).The analysis showed that,the coefficient of variation of soil nutrients in each zoning decreased from 25% ~ 52.3% to 14.7% ~ 51.5% in May 2016,and the coefficient of variation of soil nutrients in each area decreased from 25.3% ~ 91.6% to 12.2% ~ 77.6% in September 2016.And the LSR test results showed that there were significant differences among the various zoning.The study shows that the spatial variability of farmland in Wudi County decreased,and the difference between regions was obvious.Therefore the partition results can be used as a unified operation unit for farmland water,nutrient,salinity and zoning regulation.(4)By constructing the regulation model of water and salinity,the specific irrigation amount of farmland is determined,and the prescription map of water-salt irrigation regulation is generated.Based on the spatial distribution characteristics of soil moisture,salinity and p H in Wudi County,the "water and salt homologue,water supply due to demand,adequate and multiple" irrigation scheme and the salt and alkali reduction scheme of "synergistic conditioning of agents and nutrients" were put forward.Based on the theory of nutrient balance,the nutrient balance adjustment model was used to calculate the amount of soil nutrient in each partition area and each sampling point.And the prescription map of nutrient regulation was interpolated.The results showed that the supplementation of P in each management area was the largest,of which the difference between partitions was relatively large,and the supplementation of N nutrient was in the middle,and the supplementation of K nutrients was the smallest.Accordingly,a nutrient regulation plan for "stabilizing nitrogen,increasing phosphorus,supplementing potassium at the discretion" and "quick-acting combining slow release" was put forward.This study took Wudi County as an example to analyze the descriptive statistical characteristics and spatial variation rules of soil water,nutrient and salt in coastal salinized farmland,determine the area of farmland management,and put forward a scheme for the control and control of soil water,nutrient and salt.The research results can provide reference for Wudi county to control farmland soil and improve productivity and cost saving. |
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