木薯根系的地质雷达探测方法研究

In situ detection of roots is an important method and the development tendency of root research. Study on cassava roots is the basis of cassava research and essential for high yield of cassava production. Ground penetrating radar (GPR), which is based on the propagation and reflection of pulsed high frequency electromagnetic energy, has been successfully used for roots observation. Cassava roots are shallow and horizontally distributed with little perpendicular inclination. Thus, cassava roots are easily detected by GPR. However, the detection conditions and parameter settings are still needed to be further studied. This research is firstly to study the electrical characteristics (electric conductivity and dielectric constant and so on) of soil with different texture and water content, as well as the characteristics of cassava roots at different growth periods. According to the characteristics acquired, appropriate conditions will be selected for the determination of the resolution of GPR antenna with different frequency (500,800 and 1200MHZ). Then, field detection will be carried out with GPR to observe the cassava roots. By image processing and analysis with GPR software, root distribution will be interpreted and visualized. A parameter of the electromagnetic wave will be extracted to estimate the root biomass. This project will then set up a methodology to detect cassava roots with high resolution and accuracy. The results will extend the application of GPR in in situ research of roots and also provide new methodology for cassava research.

根系的原位无损观测是目前根系研究的重要手段和发展趋势。对木薯根系的原位无损观测是木薯相关研究的重要基础，也是改进木薯生产技术、提高木薯单产、缓解我国木薯需求缺口的重要途径。地质雷达技术是基于介质的电性特征差异的物探技术，已成功地应用于植物根系的研究。木薯根系分布浅，适合地质雷达探测。但其探测条件、参数设置等方面还需深入研究。本研究拟通过获取与地质雷达探测相关的土壤（不同质地和水分）和木薯根系的电性特征和电导率，选择适合的探测条件，确定不同频率(500-1200MHZ)的雷达天线的根系分辨率。根据上述参数在田间获取图像后，通过图像的后期处理，提取木薯根系分布的相关参数。并找到一个合适的地质雷达波参数，与实测的根系特征之间具有相关性，用于估算木薯产量，并采用实地开挖进行参数校正。形成木薯地质雷达探测的高精度、高准确率方法。本研究的结果将扩展地质雷达在作物根系探测上的应用，为木薯研究提供新方法。

对植物根系的无损观测是目前根系研究的重要方向。木薯块根分布较浅，适合探地雷达观测。该项目主要研究内容包括获取了木薯块根在地下的分布状态，开展了不同质地土壤在不同水分下用探地雷达探测木薯的室内模拟探测实验，和田间探测木薯。其结果表明：500MHZ天线由于无法区分相邻的木薯，难以适应木薯探测。800MHZ和1200MHZ可分辨水平间距＞7cm的木薯。探地雷达对水平间距较接近(约30cm)的垂直两层木薯探测效果较差，但水平间距为60cm时，可探测出垂直两层的木薯，但难以确定底层的准确位置。随着土壤水分增加，砂质壤土中的800MHZ和1200MHZ雷达波波速逐渐下降，探测深度也降低，探地雷达分辨木薯的能力逐渐减弱。在模拟试验探测过程中形成了一套探地雷达走线辅助装置和一套为大量土壤均匀加水的方法。项目将为木薯的地质雷达探测提供基本参数和依据。