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

农业中正在采用的精确管理系统需要关于土壤水分波动的性质及其对土壤中发生的许多生化反应的影响的详细空间信息。这对于碳封存和温室气体产生问题尤为重要。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，以及对现代实地工具的专门监测，结合传统的土壤调查地图，帮助建立详细的实地管理区。非接触式磁感应探头，如Geonics EM38的型号，一直是描述土壤电导率空间变化的流行仪器，这种空间变化被解释为与土壤水分和盐分水平有关。EM38还能够测量土壤磁化率，而土壤磁化率受含铁矿物的数量和矿物组成的影响。土壤中水分的波动与整个土壤中氧化铁(铁锈)的性质之间的密切关系，被广泛用于根据排水级别来区分它们。这种目视技术的局限性在于，现场观测(可能出现蓝色微光和红色斑驳)需要挖掘一个小坑或扩大到一米深--这两种程序都很费力，因此对全面绘制区域地图没有特别的帮助。这项研究的重点是评估磁化率双频测量的有效性，以提高我们在场水平上描绘闪烁和斑驳的能力。它基于一个公认的理解，即随着磁场频率的变化，氧化铁的结晶性质会影响它们的相对磁化率。Geonics Limited是一家加拿大公司，是电磁场仪器的国际领导者，广泛应用于农业和环境领域，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.