Topsoil Moisture Measurement Using A Dielectric Constant Method

As an important environmental element and the significant component of ecosystems, soil directly participates in nutrient and energy circulations of the system. In order to improve the efficiency of agricultural production and to promote the material and energy cycles of nature, the modern information society proposed new demand for soil environmental monitoring. Relatively outdated accesses to information and information processing methods have become bottleneck areas for the further development of modern precision agriculture.Soil moisture conditions often affect the study results of agricultural science, water science and meteorological science. However, current soil moisture instrument conditions can only get deep layer’s water content. Basing on watered soil’s dielectric model, this paper try to migrate the deep buried soil water measurement to shallow layer’s (5cm thick soil layer) application. soil moisture conditions used to obtain shallow. By improving the probe structure, it got an effective access to the 0-5cm thick soil layer’moisture content. Content and main results of this study are as follows:In order to migrate the deep buried soil water measurement to shallow layer’s (5cm thick soil layer) application, this paper introduce a new parallel probe structure. Next, it used three-dimensional electromagnetic simulation software HFSS to verify the reasonableness of the proposed probe structure. In the plant of HFSS, a model of new probes and a model of probe-soil system was established and solved to analysis the probe’s impedance changes. The theoretical results of HFSS model shown that the newly-established parallel probes could achieve electromagnetic coupling through the filled moisten soil among them. It persuasively illustrated that the new probe could be used to measure 5cm thick soil layer’s water condition. At the same time, the theoretical results of HFSS model also shown that the degree of sensitivity of the sensor would increase along with the decrease of length L or the distance d of probes.Organic solution experiment and drying method experiment were designed to verify the above analysis. Prior to this, it verify the influence of probes’ parameters in the sensor’s sensitivity by control variable method. The results of organic solution experimental shown that the newly-produced FD moisture sensor’s output voltage could represent the 0-5cm shallow soil’s water content to a certain extent. By actual measurement of 5cm thick soil layer, drying method proved that it’s possible to applied dielectric theory to the surface soil moisture measurements. This result complements the deep soil moisture measurements.