膜下滴灌棉田Dobson介电模型参数修改及水盐含量反演

Parameter Modification of Dobson Dielectric Model and Water and Salt Content Inversion in Drip Irrigation Cotton Field Under Film

新疆土壤盐渍化严重,亟需防治土壤盐渍化继续蔓延,水盐含量能直观表述盐渍化程度,所以反演土壤水盐含量对于土壤盐渍化的防治具有重要意义。以新疆典型的膜下滴灌棉田土壤为例,利用探地雷达250 MHz和1000 MHz两个频率天线,通过共中心点法获取波速后转换为视在介电常数,结合野外实测数据,修正胡庆荣盐渍土介电模型参数,以修正后的胡庆荣盐渍土介电模型反演膜下滴灌棉田表层土(0~30 cm)的水盐含量,最终验证反演结果的适用性。结果表明:通过修正胡庆荣介电模型中的参数,使该模型可以适用于膜下滴灌棉田土壤水盐含量的反演。参数A修正后的取值在0.74左右,参数ξ修正后的取值在0.14左右。②1000 MHz频率天线反演的含水量优于250 MHz频率,且反演值与实际值具有较好的线性拟合关系,R2=0.948,RMSE为2.67 cm^(3)/cm^(3)。③探地雷达250 MHz和1000 MHz频率天线的组合能够有效反演膜下滴灌棉田表层土的含盐量,反演值与实测值拟合程度较高,R^(2)=0.835,RMSE为1.43 g/kg。探地雷达技术结合参数修正后的胡庆荣介电模型不仅提高了水盐含量的调查效率,还有利于绘制中尺度棉田土壤水盐含量分布图,为防治土壤盐渍化提供了理论数据支持。

Soil salinization is serious in Xinjiang,and it is urgent to prevent the spread of soil salinization.Water and salt contents can directly indicate the degree of salinization,so their rapid inversion is of great significance for preventing soil salinization.In this paper,typical cotton fields with drip irrigation under mulch were selected in Xinjiang,wave velocities were obtained with 250 MHz and 1000 MHz antennas of ground penetrating radar(GPR)through common center point method and were converted to apparent dielectric constants.Meanwhile,combined with field measured data,the parameters in Hu Qingrong dielectric model of saline soil were modified,water and salt contents in topsoils(0-30 cm)of selected cotton fields were inversed by the modified model,and the inversion results were also verified.The results showed that the corrected value was 0.74 for parameter A and 0.14 for parameterξin Hu Qingrong dielectric model,and the modified model was feasible for the inversion of soil water and salt contents in cotton fields with drip irrigation under film.Water content inversed better by 1000 MHz frequency antenna than by 250 MHz frequency,and inversed value had significant linear correlation with measured one(R2=0.948,RMSE=2.67 cm^(3)/cm^(3)).Salt content in topsoil of cotton field could be effectively inversed by combining 250 MHz and 1000 MHz frequency antennas of GPR,and inversed value fitted well with measured one(R^(2)=0.835,RMSE=1.43 g/kg).In conclusion,the modified model combined with GPR could not only improve the survey efficiency of water and salt contents in cotton fields,but also helped edit the distribution map of soil water and salt contents in cotton fields at meso-scale,which provided theoretical data support for soil salinization prevention.