Research on the inversion model for soil conductivity of cotton field using EM38-MK2 data in southern Xinjiang
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College of Plant Science, Tarim University

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National Key Research and Development Program (Nos.2018YFE0107000,2016FYC0501407)

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    Abstract:

    【Objective】 Soil salinization is the major obstacle restraining high quality and high yield of cotton in South Xinjiang, and rated irrigation can effectively alleviate soil salinization. EM38-MK2 can be used to obtain real-time dynamical soil salinization data, monitor in-situ soil salinization in time, and provide a digital basis for rated irrigation in cotton fields. 【Method】 In this study, different soil sampling schemes were designed in line with the designing of the transmitting coil and receiving coil of the electromagnetic sensor(EM38-MK2), and soil apparent electrical conductivities (ECa) and soil samples from corresponding soil profiles were collected in the same field in six different time periods for analysis of, effects of soil sampling scheme and soil moisture content on accuracy of the apparent EC model, and specification of factors for building apparent EC models for different soil layers. Moreover, comparison was done of the local model based on data of a single period with the model based on overall data of the six periods in inversion accuracy.【Result】 Results show that the model based on single point sampling at the site of the transmitting coil of the EM38-MK2 was higher in sensoring accuracy and stability than the others and hence could effectively minimize the error caused by sampling. When soil moisture content was less than 10%, the correlation between apparent EC and measured EC was low, with determination coefficient being 0.58 and the inversion model could only roughly estimate EC; When it was more than 10%, apparent EC displayed a good relationship with measured EC, with determination coefficient being 0.80 and the inversion model could make an estimation of EC close to the measured one. The EMH+EMV model was built on the equation of ECh0.375 +(ECh0.75 +EC v0.75)/2+ECv1.5 defined as modeling factor and much higher than the EMH or EMV model in inversion accuracy with predicted apparent EC being very approximate to measured EC. The local models for predicting ECs in various soil layers different in depth were all higher than the overall one in inversion accuracy and their RPDs were more than 2.0, which indicate that they have high prediction ability. 【Conclusion】 All the findings in the study demonstrate that sampling under the transmitting coil is conducive to stability of the sampling, which may guide future utilization of the equipment, and open up new ways of thinking and server as reference for monitoring soil salinization dynamically with the electromagnetic sensor technology on the field scale.

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LIU Xinlu, PENG Jie, FENG Chunhui, WU Jialin, LUO Defang, QI Wei. Research on the inversion model for soil conductivity of cotton field using EM38-MK2 data in southern Xinjiang[J]. Acta Pedologica Sinica,2020,57(3):646-655.

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History
  • Received:January 29,2019
  • Revised:May 14,2019
  • Adopted:June 05,2019
  • Online: March 02,2020
  • Published: