Delineation of Management Zones for Site-Specific Information about Soil Fertility Characteristics through Proximal Sensing of Potato Fields

The delineation of management zones (MZs) has been suggested as a solution to mitigate adverse impacts of soil variability on potato tuber yield. This study quantified the spatial patterns of variability in soil and crop properties to delineate MZs for site-specific soil fertility characterization of potato fields through proximal sensing of fields. Grid sampling strategy was adopted to collect soil and crop data from two potato fields in Prince Edward Island (PEI). DUALEM-2 sensor, Time Domain Reflectometry (TDR-300), GreenSeeker were used to collect soil ground conductivity parameter horizontal coplanar geometry (HCP), soil moisture content (θ), and normalized difference vegetative index (NDVI), respectively. Soil organic matter (SOM), soil pH, phosphorous (P), potash (K), iron (Fe), lime index (LI), and cation exchange capacity (CEC) were determined from soil samples collected from each grid. Stepwise regression shortlisted the major properties of soil and crop that explained 71 to 86% of within-field variability. The cluster analysis grouped the soil and crop data into three zones, termed as excellent, medium, and poor at a 40% similarity level. The coefficient of variation and the interpolated maps characterized least to moderate variability of soil fertility parameters, except for HCP and K that were highly variable. The results of multiple means comparison indicated that the tuber yield and HCP were significantly different in all MZs. The significant relationship between HCP and yield suggested that the ground conductivity data could be used to develop MZs for site-specific fertilization in potato fields similar to those used in this study.

The Potential Use of Ground Conductivity Meters to Identify the Location of Seepages—Case Study of the Maniów Levee near Krakow, Poland

This paper presents an assessment of the potential usefulness of the Ground Conductivity Meter (GCM) method to locate seepage pathways in the Maniow levee zone near Kraków, Poland. We have realized this aim through geological recognition of the study area, which requires the implementation of GCM data inversion measured in the sounding version. The GCM measurements were performed along with the net of profiles using combined data from CMD Mini Explorer and CMD Explorer equipment. The methodology of the one-dimensional (1D) inversion of the GCM soundings located along profiles is presented in the article. The legitimacy of the inversion and the relationship of the results obtained in the form of conductivity sections along profiles with geology have been verified in detail. The inversion procedures were tested on the synthetic GCM soundings obtained from modeling processes, by using the electrical conductivity and thicknesses, known from the drilled formations and additionally based on DC-R sounding data. These soundings were performed at some selected reference points in the levee zone. We have used our software and IX1D Interpex software to calculate the forward modeling. Quantitative interpretation processed along the profiles has been proceeded by 1D inversion of GCM data at several referential points located close to boreholes and DC soundings. It was done to verify the correctness of the quantitative interpretation. The geoelectrical models, obtained in a section form, were correlated with the borehole lithology data, providing a reference geological structure in some places. As a result of the work mentioned above, the potential seepage zones were located on the conductivity sections. The thickness of the cohesive silty clay layer, lying near to the surface, in the seepage zones, was thin enough and less than a meter. When the water level in the Vistula river was high enough, water can flow in the noncohesive gravel layer occurring directly below the silty clays and lead to flooding on the landward side of the dams in the Maniow region.

A New Approximate Method for Lightning-Radiated ELF/VLF Ground Wave Propagation over Intermediate Ranges

A new approximate method for lightning-radiated extremely low-frequency (ELF) and very low-frequency (VLF) ground wave propagation over intermediate ranges is presented in this paper. In our approximate method, the original field attenuation function is divided into two factors in frequency domain representing the propagation effect of the ground conductivity and Earth’s curvature, and both of them have clearer formulations and can more easily be calculated rather than solving a complex differential equation related to Airy functions. The comparison results show that our new approximate method can predict the lightning-radiated field peak value over the intermediate range with a satisfactory accuracy within maximum errors of 0.0%, −3.3%, and −8.7% for the earth conductivity of 4 S/m, 0.01 S/m, and 0.001 S/m, respectively. We also find that Earth’s curvature has much more effect on the field propagation at the intermediate ranges than the finite ground conductivity, and the lightning-radiated ELF/VLF electric field peak value (V/m) at the intermediate ranges yields a propagation distance d (km) dependence of d−1.32.

Integrated Very Low Frequency Electromagnetic (Vlf-Em) Geophysical And Hydrogeochemical Study Of Abeku Dumpsite In Ibadan, Southwestern Nigeria

Very Low Frequency Electromagnetic (VLF-EM) and hydrogeochemical studies have been integrated to measure ground conductivity and also determine the concentration of leachate derived contaminants in the groundwater around Abeku dumpsite in Ibadan, southwest Nigeria. Ten (10) VLFEM profiles were occupied within and around the dumpsite fence. Water sample from wells were also analyzed to determine the concentration of pollutants in the study area. Qualitative interpretations of VLF-EM results indicate relatively high ground conductivity within the dumpsite, which decreases away from the actual waste dump phase of the dumpsite. Ground conductivity is relatively higher in the south and east of the dumpsite which are located downhill of the groundwater hydrostatic head when compared with the north and west of the study area situated uphill of hydraulic gradient. Hydrogeochemical analyses present NO3−, SO42− and PO42− ions concentration in the range of 9.24 – 13.64 mg/L, 3 – 12 mg/L and 0.33 – 1.07 mg/L respectively. The SO42− and PO42− ions concentrations are within permissible limits, while the NO3− ion concentration is slightly above the Federal Ministry of Environment’s standard for potable water in Nigeria.

Applying Petroleum Pressure Buildup Well Test Procedure on Thermal Response Test—A Novel Method to Improve Accuracy of Thermal Conductivity Determination

Theory of the Thermal Response Testing (TRT) is a well-known part of sizing process of the geothermal exchange system. Multiple parameters influence accuracy of effective ground thermal conductivity measurement; like testing time, variable power, climate interferences, groundwater effect etc. To improve accuracy of the TRT we introduced procedure to additionally analyze falloff temperature decline after power test. Method is based on a premise of analogy between TRT and petroleum well testing, since origin of both procedures lies in diffusivity equation with solutions for heat conduction or pressure analysis during radial flow. Applying pressure build-up test interpretation technique to the borehole heat exchanger testing, greater accuracy could be achieved since ground conductivity could be obtained from this period. Analysis was conducted on coaxial exchanger with five different power steps, and with both direct and reverse flow regime. Each test was set with 96hr of a classical TRT, followed by 96hr of temperature decline, making it almost 2000 hours of cumulative borehole testing. Results showed that ground conductivity value could vary as much as 25% depending on test time, seasonal period and power fluctuations while thermal conductivity obtained from a falloff period gives more stable values with only 10% value variation.

The Effect of Direct Lightning Shielding Rod on Lightning Electromagnetic Fields Aboveground

A practical new type direct lightning shielding rod is designed to reduce the electromagnetic radiation produced by lightning stroking to Franklin lightning rod in the paper. The Finite-Difference Time-Domain (FDTD) method is adopted for analyzing. It is the shielding layer that affects the electromagnetic fields and the insulating medium make no difference. All the electromagnetic fields amplitude obtained decrease for the shielding layer existing, regardless of any condition, but the extent is different. That is, the effect on the horizontal electric field is most noticeable, the vertical electric field comes second, minimum the azimuthal magnetic field. All the field components are affected by shielding layer height and the distance between shielding layer and lightning channel, but not significantly by the shielding layer grounding depth. The shielding effect is more obvious with lower ground conductivity, but the ground relative permittivity makes no difference.

An analytical expression for early electromagnetic signals generated by impulsive line-currents in conductive Earth crust, with numerical examples

<p>Changes in the electromagnetic (EM) field after an earthquake rupture but before the arrival of seismic waves (“early EM signals”) have sometimes been reported. Quantitative evaluations are necessary to clarify whether the observed phenomena are accounted for by known theories and to assess whether the phenomenon can be applied to earthquake early warning. Therefore, analytical expressions for the magnetic field generated by an impulsive line-current are derived for a conductive half-space model, and for a two-layer model; the somewhat simpler situation of a conductive whole-space is also considered. By analyzing the expressions obtained for the generated EM field, some expected features of the early EM signals are discussed. First, I verify that an early EM signal arrives before the seismic waves unless conductivity is relatively high. Second, I show that early EM signals are well approximated by the whole-space model when the source is near the ground surface, but not when it is at depth. Third, I show that the expected amplitudes of early EM signals are within the detection limits of commonly used EM sensors, provided that ground conductivity is not very high and that the source current is sufficiently intense. However, this does not mean that the EM signals are easily distinguishable, because detector sensitivity does not account for additive noise or false positive detections.</p>