In-field Dual-Frequency Characterization of Soil Magnetic Susceptibility Dynamics

在农业中不断采用精确管理系统需要关于土壤湿度波动性质及其对土壤中发生的许多生物化学反应的影响的详细空间信息。这对碳固存和温室气体产生问题尤其重要。现在经常使用各种技术，包括高分辨率卫星图像和地面高程模型，以及现代田间工具上的专门监测器，再加上传统的土壤调查地图，帮助建立详细的田间管理区。非接触式磁感应探头，例如Geonics EM 38型号，已经成为表征土壤电导率空间变化的流行仪器，其被解释为与土壤水分含量和盐度水平有关。EM 38还能够测量土壤磁化率，这是由含铁矿物的数量和矿物组成的影响。水分含量的波动与整个土壤中氧化铁（铁锈）的性质之间的密切关系被广泛用于根据其排水等级来区分它们。这种目视技术的局限性在于，实地观察（可能的蓝色潜育带和红色斑点）需要挖掘一个小坑或钻到一米深-这两种程序都很费力，因此特别不利于全面绘制区域地图。这项研究的重点是评估双频测量磁化率的有效性，以提高我们的能力，描绘潜育化和斑点在外地的水平。这是基于铁氧化物的结晶性质会影响其相对磁化率，因为磁场的频率会改变。Geonics Limited是一家加拿大公司，也是电磁场仪器的国际领导者，广泛应用于农业和环境，为该项目带来了50多年的经验和专业知识。

The ongoing adoption of precision management systems in agriculture requires detailed spatial information on the nature of soil moisture fluctuations, and their impact on the many biochemical reactions occurring in soils. This is especially important for the issue of carbon sequestration and greenhouse gas production. Various technologies, including high-resolution satellite imagery and surface elevation models, as well as specialized monitors on modern field implements, combined with tradition soil survey maps, are now regularly used to help establish the detailed field management zones. Non-contacting magnetic induction probes, such as models of the Geonics EM38, have been a popular instrument for characterizing spatial variations in soil electrical conductivity, which is interpreted in relation to soil moisture content and salinity levels. The EM38 is also capable of measuring the soil magnetic susceptibility, which is influenced by the amount and mineralogical composition of iron-containing minerals present. The close relationship between fluctuations in the moisture content and the nature of iron oxides (rust), throughout the soil, is widely-used to distinguish them according to their drainage class. This visual technique is limited in that field observations (of possible bluish gleying and reddish mottling) require excavating a small pit or augering to a depth of one metre - both of these procedures are laborious, and so not especially conducive to comprehensive mapping of areas. This research is focussed on evaluating the effectiveness of dual-frequency measurements of magnetic susceptibility, to improve our ability to delineate gleying and mottling at the field level. It is based on the well-established understanding that the crystalline nature of iron oxides influences their relative susceptibility, as the frequency of the magnetic field is changed. Geonics Limited, a Canadian company and international leader in electromagnetic field instrumentation, widely-applied in agriculture and the environment, brings more than 50 years of experience and expertise to this project.