| Xinjiang oasis farmland,because of the drought climate,high salt content of parent material,in front of the closed oasis basin,land development and utilization of saline plants and other natural factors and irrational land use for a long time leads to the deterioration of the part of the soil conditions,the more productivity level,crop growth and development of the oasis is severely hampered,on the soil surface formed of different sizes,plate bare land,Most of these bare spot plots have higher salinity.The appearance of the bare spot deteriorates the soil quality and leads to the decrease of farmland productivity in oasis.Therefore,it is urgent to study the salt and alkali characteristics of bare spot.This paper took oasis farmland bare spot in Manas County,Xinjiang as the research object,combined with field experiment and laboratory analysis,precise positioning of oasis farmland bare spot was carried out through Landsat8 satellite images and UAV visible light images,and sampling analysis was carried out in September 2013 and July 2014 respectively.A soil salinity interpretation model based on EM38 was established.In this paper,the bare spot of oasis farmland was systematically classified,and finally a set of classification and retrieval system of oasis farmland bare spot was formed,and the physical and chemical properties of soil bare spot of different salinization degree were analyzed,and then corresponding improvement methods were put forward for different types of bare spot.The following conclusions are drawn:(1)Soil salinity in the study area reached moderate salinization,and its variability was strong;The conductivity values of EM38 under the two measurement modes are moderate variation.The correlation coefficients between soil salinity and EM38 conductivity increased with the increase of soil depth.(2)The soil salt interpretation accuracy of the four models based on EM38 soil apparent conductivity increases with the increase of soil depth;Among them,binary linear regression model and random forest regression model have higher interpretation accuracy,and their predicted values and measured values fit well(P<0.05).R2 range is 0.288-0.727 and 0.473～0.735,respectively.When soil depth is less than 40 cm,The interpretation accuracy of random forest regression model is slightly better than that of binary linear regression model.In the unitary linear regression model,when soil depth is less than 20 cm,the interpretation accuracy of vertical model is greater than that of horizontal model,but when soil depth is greater than 20 cm,the situation is opposite.(3)Heavy saline bare spot and saline soil bare spot had an obvious trend of salt surface accumulation,and the salt content of light saline bare spot and medium saline bare spot increased with the increase of soil depth.The coefficient of variation of soil p H in bare spot profiles of different salinization levels was weak,and the maximum coefficient of variation(9.41%)was only 1.31 times of the minimum value(7.19%).In bare spot soil,the content of silt was significantly(P<0.05)higher than that of sand and clay,the content of sand,silt and clay was 30%,49% and 21%,respectively.The content of sand decreased with the increase of soil salt content.There was no significant correlation between soil available P content and soil salt content in bare spot of different salinization degree.(4)According to the classification indexes of salt,alkali soil and texture,the bare spot in oasis farmland can be divided into 28 species.(5)Based on the classification of bare spots,the treatment methods can be classified into three categories:The first is mild and non-salinized patches.The factors that make it difficult for crops to grow in such naked patches are not salinization,but agronomic management measures and soil texture composition.Reasonable tillage and planting green fertilizer should be adopted to improve soil texture.Second,moderate,severe and saline-soil patches,where high salt content is the main obstacle to crop growth and development,can be removed by water conservancy engineering measures;The third is the plaque with high p H value and high ESP.In this type of plaque,the high concentration of exchangable sodium is mainly considered,and the alkalinity is generally neutralized by adding chemical modifiers and various acidic substances. |
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