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Near-surface soil water content (NSWC) is an important parameter for characterizing hydrological processes, water and vapor exchange at the soil-atmosphere boundary, and potential biological productivity. Here we develop a dielectric based frequency-domain (FD) impedance sensor operating at 100 MHz, with a novel coaxial probe design and a temperature sensor embedded in the circuit board. This perforated cylinder coaxial (PCC) sensor provides simultaneous measurements of volumetric soil water content (VSWC) and of temperature. The temperature measurement allows signal correction for the temperature response of the circuit board and of the permittivity of soil water. We characterize the performance of the PCC sensor and compare it with alternative 3-pin- and 2-pin-electrode FD impedance sensors each using a similarly performing circuit board. A series of theoretical analyses and experiments were conducted, including (i) sensors calibration, (ii) temperature effects and their correction, (iii) soil volume sensed by each sensor through simulation analysis and a stepwise soil removal (SSR) test and (iv) accuracy comparison of the three sensors when applied for the NSWC measurements. The calibration results verified that the PCC, 3-pin and 2-pin probes were suitable to measure VSWC (RMSE ≤ 0.0142 cm3 cm−3). The simulation analysis using High Frequency Structure Simulator software (HFSS) indicated that the novel PCC probe had a symmetrical distribution of the E-field, wholly contained within the cylinder, avoiding leakage of the E-Field into air at the soil-atmosphere interface and removing the dependency of sensed volume on VSWC. The results of the SSR test showed that the E-field distributed outside the receiving electrode of the PCC probe could be ignored whereas that of both pin-type electrodes was distributed outside of the receiving electrode to a distance that depended on VSWC (i.e. up to 8 mm for 3-pin and up to 11 mm for 2-pin designs when VSWC > 0.17 cm3 cm−3), which corresponds to the simulation analysis. Moreover, the new PCC probe provided more accurate NSWC measurement than 3-pin or 2-pin probes because the E-field was contained within the perforated cylinder, avoiding E-field leakage and fixing sensed soil volume independent of VSWC. The pin-structure probes appear to perform best when installed horizontally in the soil at least 11 mm below the surface.

The HYDRUS-2D simulation software has been used for irrigation management. Its performance under realistic irrigation regimes requires evaluation with new methodologies that integrate larger soil volumes, because soil water content is highly variable in time, space and scale. We compare direct measurements in a sloping field environment under drip irrigation with simulation using HYDRUS-2D. An advanced mobile sensor technology is used to track the dynamics of soil water content, and thus of unsaturated flow, at 0.25 m and 0.50 m depth in a field plot (6 m × 3 m; 4° slope) beneath two parallel (0.5 m separation; 7 emitters per delivery tube) dripper arrays. We document an asynchronous sequence of wetting fronts driven by the sloping surface and capture the field results well using HYDRUS-2D, in the spatial (R2 = 0.935–0.963, p

Although sticky traps are reliable indicators of pest population dynamics but pest counting by humans is time-consuming and menial labour. A novel smart vision algorithm based on two-dimensional Fourier transform (2DFT) spectrum is presented. Rather than directly counting the pests captured on the traps, the novel concept is to treat trapped pests as noise in a two-dimensional (2D) image with 2DFT serving as a specific noise collector. The research objectives included comparing human and 2DFT counting in two proof-of-principle tests: (i) simulated pests with various quantities and distributions arrayed on two series of templates using both ordered and random patterns; (ii) sweet potato whiteflies [Bemisia tabaci (Gennadius), Hemiptera: Aleyrodidae] on yellow sticky traps (YSTs) and western flower thrips [Frankliniella occidentalis (Pergande), Thysanoptera: Thripidae] on blue sticky traps (BSTs). Tests of simulated pests (2–512) on eight templates verified that the 2DFT-based index provides accurate estimates of pests captured on the traps (R2 = 1), independent of pest distribution pattern. High correlations were obtained from count results of whiteflies on 34 YSTs (R2 = 0.9994) and thrips on 33 BSTs (R2 = 0.9989). Measurement errors were addressed.

Hot vegetable oil can be used for weed control as an alternative to the use of herbicides. We analysed the temporal development of vegetable oil mineralization in soil and tested the role of nutrient supply on oil mineralization. Further, we investigated the effect of oil application on mineralization of native soil organic carbon (SOC), i.e. the priming effect. In a laboratory experiment, three oil dosages (0.1, 1.0 and 3.0ml per 35g soil) were applied to three arable soils and soil respiration was measured hourly. Both a C3-sunflower oil and a C4-corn oil were used in order to differentiate oil-derived CO2 from SOC-derived CO2. The results revealed that after 42days of incubation, 9.6 to 39.7% of the applied oil was mineralized which, however, also primed the mineralization of SOC by a factor of 2.2 to 4.2. The higher the applied oil amount, the lower was the percentage of oil-C mineralization, but the higher was the priming effect. The addition of fertilizer (0.29mgNg(-1) soil and 0.048mgPg(-1) soil) increased oil-C mineralization to 39.9 to 50.9%. We conclude that oil can temporarily accumulate in soil, especially in case of low nutrient supply. As the addition of oil stimulates SOC mineralization, a decrease of native SOC stocks may occur, which needs further quantification in long-term field experiments.

Evapotranspiration (ET) plays an important role in water and energy balance at the surface-atmosphere interface. It is widely reported that near-surface soil water content (SWC) or soil water potential (SWP) significantly affects ET and this parameter has been incorporated into the FAO Penman-Monteith (FAO-PM) model for prediction of ET during crop growth seasons. However, there is little information on the effect of SWC or SWP on prediction of ET during soil freeze-thaw cycles in winter. We present an experiment conducted at a demonstration farm with a crop of winter wheat, over two winters near Beijing, China. A lysimeter system equipped with a weather station was used to measure the ET flux and meteorological data. Unfrozen soil water content (USWC) and soil temperature (Tsoil) were measured using dielectric tube sensors (DTS) and digital temperature sensors, respectively. SWP was determined by measured USWC and a soil moisture characteristic (SMC) curve derived from the soil freezing characteristic (SFC) curve and the Clapeyron equation in frozen soil. Detailed measurements in year 1 showed that the FAO-PM model exhibited a complex error pattern, underestimating ET from unfrozen soil but overestimating ET from stable frozen soil. To address these errors, we define a freezing stress index (Ksf) as a function of SWP. Incorporation of Ksf as a modifier of the standard crop coefficient in the FAO-PM model improved prediction of ET (RMSE declined from 0.424 to 0.187 mm day−1, in year 1). These data revealed a correlation between SWP near the soil surface (

One role of stems is that of water storage. The water content of stems increases and decreases as xylem water potential increases and decreases, respectively. Hence, a nondestructive method to measure stem water content (StWC) = (volume of water) : (volume of stem), could be useful in monitoring the drought stress status of plants. We introduce a frequency domain inner fringing capacitor-sensor for measuring StWC which operates at 100 MHz frequency. The capacitor-sensor consists of two wave guides (5-mm-wide braided metal) that snugly fit around the surface of a stem with a spacing of 4-5 mm between guides. Laboratory measurements on analog stems reveals that the DC signal output responds linearly to the relative dielectric constant of the analog stem, is most sensitive to water content between the waveguides to a depth of c. 3 mm from the stem surface, and calibrations based on the gravimetric water loss of excised stems of plants revealed a resolution in StWC of < ± 0.001 v/ v. The sensor performed very well on whole plants with a 100-fold increased resolution compared with previous frequency domain and time domain reflectometry methods and, hence, may be very useful for future research requiring nondestructive measurements of whole plants.

Today's agricultural engineering is characterised by automation and information technology. Automatic steering systems have become an adequate tool for guidance on a track with accuracy in the range of centimetres. Consequently, the transition from track to track must be planned exactly, so that the target track is achieved precisely. A method which can generate turn trajectories – so-called headland turns - with smooth transition and a fast computation performance is investigated. The method is based on the continuous-curvature path planning in the field of mobile robotics and is connected to the specific agronomic requirements. In this context the clothoid construction element constitutes the main construction element. It enables the smooth connection from zero curvature to maximal curvature which represents the reciprocal of the minimal turning radius. In totality, a manoeuvre can be planned with modified Dubins curves, both going backwards and forwards is feasible with modified Reeds and Shepp curves. Seven different manoeuvres are useful from an agronomic point of view. It is shown that all turn manoeuvres are feasible with this method. Also an analysis regarding the trajectory length, the headland width and the operation time is shown.

The Deans' switch is an effluent switching device based on controlling flows of carrier gas instead of mechanical valves in the analytical flow path. This technique offers high inertness and a wear-free operation. Recently new monolithic microfluidic devices have become available. In these devices the whole flow system is integrated into a small metal device with low thermal mass and leak-tight connections. In contrast to a mechanical valve-based system, a flow-controlled system is more difficult to calculate. Usually the Deans' switch is used to switch one inlet to one of two outlets, by means of two auxiliary flows. However, the Deans' switch can also be used to deliver the GC effluent with a specific split ratio to both outlets. The calculation of the split ratio of the inlet flow to the two outlets is challenging because of the asymmetries of the flow resistances. This is especially the case, if one of the outlets is a vacuum device, such as a mass spectrometer, and the other an atmospheric detector, e.g. a flame ionization detector (FID) or an olfactory (sniffing) port. The capillary flows in gas chromatography are calculated with the Hagen-Poiseuille equation of the laminar, isothermal and compressible flow in circular tubes. The flow resistances in the new microfluidic devices have to be calculated with the corresponding equation for rectangular cross-section microchannels. The Hagen-Poiseuille equation underestimates the flow to a vacuum outlet. A corrected equation originating from the theory of rarefied flows is presented. The calculation of pressures and flows of a Deans' switch based chromatographic system is done by the solution of mass balances. A specific challenge is the consideration of the antidiffusion resistor between the two auxiliary gas lines of the Deans' switch. A full solution for the calculation of the Deans' switch including this restrictor is presented. Results from validation measurements are in good accordance with the developed theories. A spreadsheet-based flow calculator is part of the Supporting Information.

To ensure penetration results that are comparable under various experimental conditions, cone penetrometers specified by ASABE Standards have been suggested for many years. Elastic-plastic properties are typical of most agricultural materials, so the material being penetrated by a cone penetrometer may contact the penetrometer shaft, and friction on the shaft may affect the penetration force data. Development of a method for quantifying this friction force is expected to improve the accuracy of cone penetrometer data. The objectives of this study were: (1) to evaluate a method for determining friction force on the shaft of a cone penetrometer while penetrating sand and clay soils packed in a specific cylinder, (2) to verify the penetration friction component (PFC) that may significantly influence penetration resistance (PR) measurements for various densities of chopped maize, and (3) to assess the effectiveness of a proposed filter method for adjusting friction on the penetrometer shaft. With these intentions, we embedded strain gauges into an ASABE Standard small cone. The tip was free from the shaft friction, so the output of this sensor was used as a reference in this study. We found the ASABE Standard small cone suitable for a broad range of soil textures, as little PFC was observed from the sand or the clay soil samples. However, considerable friction from penetrating chopped maize was observed at three levels of packed density using the cylinder method. In this situation, with the reference of the sensor output inside the tip, a pair of coefficients (C 1 = 2329, C 2 = 2120) were optimized to filter the PFC out of the PR measurement. The adjusted data agreed well with those of the reference sensor (R 2 = 0.968; RMSE = 6.521 N). Thus, ASABE Standard penetrometers can also be used for silage materials without mechanical modification.

Precision-farming applications are mainly based on site-specific information of soil properties at the field scale. For this purpose, a number of novel sensor techniques have been developed but not intensively tested under different field conditions. This study presents a combined application of a self-developed dual-sensor vertical penetrometer (DVP) for measuring volumetric soil water content (VSWC) and cone index (CI), and an EM38 for soil apparent electrical conductivity (ECa) in a pasture (1.4 ha). To verify the feasibility of the DVP for interpreting the depth-specific information in the field, not only the soil physical properties and their geographical coordinates were measured, but also geo-referenced yield data were collected. We found that the yield pattern was quite similar to the soil water-content pattern of each layer (layer-1: 5–15 cm; layer-2: 15–25 cm, layer-3: 25–35 cm) and ECa pattern. Using the map-based comparisons in conjunction with the statistical analyses, the effect of each measured soil physical property (VSWC, CI, and ECa) on the yield was investigated. The regression between the yield and VSWC at each layer fitted a quadratic equation (R2 = 0.515 at 5–15 cm; R2 = 0.623, at 15–25 cm; R2 = 0.406 at 25–35 cm). The negative correlation between yield and CI at each layer fitted a linear model with R2 ≥ 0.510.

To realize site-specific and variable-rate application of agricultural pesticides, accurately metering and controlling the chemical injection rate is necessary. This study presents a prototype of a direct nozzle injection system (DNIS) by which chemical concentration transport lag was greatly reduced. In this system, a rapid-reacting solenoid valve (RRV) was utilized for injecting chemicals, driven by a pulse-width modulation (PWM) signal at 100 Hz, so with varying pulse width the chemical injection rate could be adjusted. Meanwhile, a closed-loop control strategy, proportional-integral-derivative (PID) method, was applied for metering and stabilizing the chemical injection rate. In order to measure chemical flow rates and input them into the controller as a feedback in real-time, a thermodynamic flowmeter that was independent of chemical viscosity was used. Laboratory tests were conducted to assess the performance of DNIS and PID control strategy. Due to the nonlinear input-output characteristics of the RRV, a two-phase PID control process obtained better effects as compared with single PID control strategy. Test results also indicated that the set-point chemical flow rate could be achieved within less than 4 s, and the output stability was improved compared to the case without control strategy.

A simple and robust monodroplet generator was constructed for drop-on-demand application of aqueous solutions of pesticides to crop plants and weeds. A short current impulse regulated the opening of a solenoid valve, allowing pressurised nitrogen gas to flow into a liquid chamber. Once a jet is released from the nozzle, one single droplet is detached, and the remaining part is retracted back into the cylinder as the excess gas is exhausted. The effects of the impulse width, pressure, diameter of the orifice, and the surface tension of the liquids as influenced by adjuvants were evaluated in terms of droplet diameter and generation potentiality. In general, increasing the impulse width and orifice diameter led to an increase in the droplet diameter. In contrast, increased pressure and reduced surface tension of the liquid led to a decreased diameter, although the effect was observed only at lower impulse widths and larger orifice diameters. With an optimum adjustment, we were able to generate monodroplets with diameters ranging from 533 to 1819 μm, although the range could be varied easily by changing the parameters.

Topsoil porosity (TSP) is an important parameter for the research of soil physics, agriculture and environmental protection. However, the traditional method for measuring porosity is time consuming. Conversely, a series of new methods measuring soil surface roughness (SSR) are increased and become more and more quickly. Some researchers propose to predict TSP by SSR. In this study, two fields cultivated by different tillage type were investigated under natural condition during four years (2006-2009). The results of this study show that (i) both of soil roughness and porosity are decreased over time; (ii) there are strong correlation between soil porosity and roughness effected by rainfall; (iii) after introduce the index of accumulative mean rainfall (AMR), a model of multiple linear regression for presenting the correlation among SSR, TSP and rainfall was built using sampling data of 2006-2009 with R2>0.7.

Plants respond to drought stress with different physical manners, such as morphology and color of leaves. Thus, plants can be considered as a sort of living-sensors for monitoring dynamic of soil water content or the stored water in plant body. Because of difficulty to identify the early wilting symptom of plants from the results in 2D (two-dimension) space, this paper presented a preliminary study with 3D (three-dimension)-based image, in which a laser scanner was used for achieving the morphological information of zucchini ( Cucurbita pepo ) leaves. Moreover, a leaf wilting index (D LWIF ) was defined by fractal dimension. The experiment consisted of phase-1 for observing the temporal variation of D LWIF and phase-2 for the validation of this index. During the experiment, air temperature, luminous intensity, and volumetric soil water contents (VSWC) were simultaneously recorded over time. The results of both phases fitted the bisector (line: 1:1) with R 2 =0.903 and REMS=0.155. More significantly, the influence of VSWC with three levels (0.22, 0.30, and 0.36 cm 3 cm −3 ) on the response of plant samples to drought stress was observed from separated traces of D LWIF . In brief, two conclusions have been made: (i) the laser scanner is an effective tool for the non-contact detection of morphological wilting of plants, and (ii) defined D LWIF can be a promising indicator for a category of plants like zucchini.

A direct injection system that injects pesticides locally at all nozzles on a boom was assembled and investigated under laboratory conditions with regards to its ability to be cleaned. The system was contaminated with a safe-to-use polyvinylpyrrolidone-water solution as a test pesticide before cleaning. The cleaning process was divided into two steps: 1) reclaiming the simulated pesticide by pushing it back into the pesticide tank using pressurised air (pre-cleaning) and 2) rinsing the contaminated part of the hydraulic system with water. Cleaning performance was investigated systematically to ascertain the initial dynamics of the rinsing process as well as long term cleaning. Evaluations included variation of 1) pre-cleaning time and 2) water inlet position. Measurements showed that the concentration of the simulated pesticide in the rinsing water could initially be as high as 30%. As the pre-cleaning time was extended the initial concentration was reduced by one third. Changing the water inlet position reduced the initial concentration of the simulated pesticide in the rinsing water to 5%. These concentrations were much higher than in most common spray solutions. This means that if an active pesticide was used further dilution of the pesticide concentration in the rinsing water would be required for it to be sprayed on a crop. In some cases it took more than 10 min to dilute simulated pesticide residues in a 3 m test section down to 0% which clearly shows the need for more research on factors influencing the cleaning process and more development of cleaning processes.

Real-time controlled pesticide application requires a fast reacting system, enabling continuous variation of pesticide type and concentration based on a control signal. Direct injection systems meet the requirements for such application; however there are significant differences in the response time and quality of single system designs. This article discusses the complex of problems in direct injection systems in connexion with real-time control and proposes optimisations of system parts in order to reduce the response time and improve the quality of the process. The system response time was reduced to 160 ms for 1% output concentration by optimization of the control process, injection assembly and mixing chamber design.

Plant growth and crop yield can be significantly impeded by a number of soil physical parameters including soil water content, mechanical strength and soil electrical conductivity (EC). Therefore, to simultaneously measure these physical parameters along vertical depths in the field, it has been desired for many years. This study focused on developing a multi-sensor system, which contained a cell with three sensors for measuring soil water content, mechanical strength and EC. Additionally a Hall-current sensor was proposed to measure the operating current of a dc-motor, which generated the penetrating force during operating process. Based on the theoretical analysis of the transformation from electrical to mechanical energy, it was feasible to evaluate the soil mechanical strength from the operating current of the dc-motor. In order to verify the performance of the designed system and the theoretical analysis addressed, relevant calibrations and tests were conducted. The results demonstrate that the multi-sensor system could be beneficial and practical for field surveys.

Growing industrialization and its implication to nuisance smells led to an increased interest in odour monitoring. As a result of that a variety of sensors and methods to detect or analyse odour were developed over the last few years. The function of the chemosensor system combined with a pre-concentrated unit is explained. The concept and implementation of an odour measuring method using a chemosensor system in combination with olfactometry is described. The odour measurement system was installed at the outlet of a charcoal filter at a waste incineration plant. For a period of three months the system operated unsupervised, taking odour samples continuously, calculating the odour concentration online and signaling odour events to a control centre. The method of odour measurement has proven successful and has shown the feasibility of detecting a filter breakthrough using a chemosensor system.

Oxygen (O2) concentration inside the substrate is an important measurement for silage-research and-practical management. In the laboratory gas chromatography is commonly employed for O2 measurement. Among sensor-based techniques, accurate and reliable in situ measurement is rare because of high levels of carbon dioxide (CO2) generated by the introduction of O2 in the silage. The presented study focused on assessing three types of commercial O2 sensors, including Clark oxygen electrodes (COE), galvanic oxygen cell (GOC) sensors and the Dräger chip measurement system (DCMS). Laboratory cross calibration of O2 versus CO2 (each 0–15 vol.%) was made for the COE and the GOC sensors. All calibration results verified that O2 measurements for both sensors were insensitive to CO2. For the O2 in situ measurement in silage, all O2 sensors were first tested in two sealed barrels (diameter 35.7 cm; height: 60 cm) to monitor the O2 depletion with respect to the ensiling process (Test-A). The second test (Test-B) simulated the silage unloading process by recording the O2 penetration dynamics in three additional barrels, two covered by dry ice (0.6 kg or 1.2 kg of each) on the top surface and one without. Based on a general comparison of the experimental data, we conclude that each of these in situ sensor monitoring techniques for O2 concentration in silage exhibit individual advantages and limitations.

A combined penetrometer is an appropriate tool to measure the soil cone resistance and the water-content profile. As a relatively new technique, a combined capacitance-penetrometer for the simultaneous measurement of cone index and soil water content was developed at the Department of Agricultural Engineering of Bonn University in 2002. The objective of this study was the evaluation of the effectiveness and applicability of the innovated penetrometer with a focus on three aspects: (1) A capacitance sensor with two electrode configurations was calibrated for silt loam, sandy loam, and sand. The calibration results show that both electrode configurations have sufficient water-content sensitivity, but soil-specific calibrations seem necessary. (2) Under laboratory conditions, the dynamic resolution and response of the capacitance-penetrometer were validated, and its radius of influence was determined. (3) The field measurement results demonstrate that this measurement technique can be used to improve the interpretation quality of soil cone index data. Bewertung eines Penetrometers zur gleichzeitigen Bestimmung von Eindringwiderstand und Bodenfeuchte Fur die Ermittlung von Bodenprofilen fur den Eindringwiderstand und die Bodenfeuchte erscheint die Kombination aus Penetrometer und Bodenfeuchtesensor als geeignete Losung. Ein solcher Kombinationssensor wurde im Jahr 2002 am Institut fur Landtechnik der Universitat Bonn fur die simultane Messung des Eindringwiderstandes und der Bodenfeuchte entwickelt. In diesem Beitrag wird die Tauglichkeit und Anwendbarkeit fur Feldmessungen in folgenden Schritten dargestellt: (1) Ein kapazitiver Sensor mit zwei Elektrodenkonfigurationen wurde fur die drei Bodenarten schluffiger Lehm, sandiger Lehm und Sand kalibiriert. Die Kalibrationsgleichungen zeigen, dass beide Elektrodenanordnungen uber ausreichende Empfindlichkeit zur Bodenfeuchtemessung verfugen. Es sind aber bodenartspezifische Kalibrierungen notwendig. (2) Die dynamische Auflosung und das Ansprechverhalten des Feuchtesensors wurden fur beide Elektrodenanordnungen untersucht, und die Ausbreitung des dielektrischen Feldes wurde bestimmt. (3) Die Ergebnisse der Messungen im gewachsenen Boden zeigen, dass die Messmethode zur Verbesserung der Interpretation der Konus-Indexwerte herangezogen werden kann.

We present a thermal desorption unit with features designed for use with chemical sensors to enhance sensitivity and selectivity. A novel method is used to measure and empirically describe influences on breakthrough characteristics. A fast heating technique and low dead volume result in sharp desorption peaks (approx. 0.53 ml). Enrichment factors of more than 100-fold allow for detection of odorous substances below their odor threshold.

Numerous vegetable oil methyl esters covering the entire range of fatty acid patterns of vegetable oils were investigated with a standard distillation apparatus. The course of the boiling curves and the suspected relationship between the drop in boiling temperatures and the start of decomposition are discussed. The suitability of the methyl esters for diesel engines was evaluated with regard to combustion conditions and specifications defined in fuel standards. The differences from regular diesel fuel are outlined.

Boar taint is a specific off-odour of boar meat products, known to be caused by at least three unpleasant odorants, with very low odour thresholds. Androstenone is a boar pheromone produced in the testes, whereas skatole and indole originate from the microbial breakdown of tryptophan in the intestinal tract. A new procedure, applying stable isotope dilution analysis (SIDA) and dynamic headspace-thermal desorption–gas chromatography/time-of-flight mass spectrometry (dynHS-TD–GC/TOFMS) for the simultaneous quantitation of these boar taint compounds in pig fat was elaborated and validated in this paper. The new method is characterised by a simple and solvent-free dynamic headspace sampling. The deuterated compounds d3-androstenone, d3-skatole and d6-indole were used as internal standards to eliminate matrix effects. The method validation performed revealed low limits of detection (LOD) and quantitation (LOQ) with high accuracy and precision, thus confirming the feasibility of the new dynHS-TD–GC/TOFMS approach for routine analysis.

With the rapid rise in demand for both agricultural crop quantity and quality and with the growing concern of non-point pollution caused by modern farming practices, the efficiency and environmental safety of agricultural production systems have been questioned (Gebbers and Adamchuk, 2010). While implementing best management practices around the world, it was observed that the most efficient quantities of agricultural inputs vary across the landscape due to various naturally occurring, as well as man-induced, differences in key productivity factors such as water and nutrient supply. Identifying and understanding these differences allow for varying crop management practices according to locally defined needs (Pierce and Nowak, 1999). Such spatially-variable management practices have become the central part of precision agriculture (PA) management strategies being adapted by many practitioners around the world (Sonka et al., 1997). PA is an excellent example of a system approach where the use of the sensor fusion concept is essential. Among the different parameters that describe landscape variability, topography and soils are key factors that control variability in crop growing environments (Robert, 1993). Variations in crop vegetation growth typically respond to differences in these microenvironments together with the effects of management practice. Our ability to accurately recognize and account for any such differences can make production systems more efficient. Traditionally differences in physical, chemical and biological soil attributes have been detected through soil sampling and laboratory analysis (Wollenhaupt et al., 1997; de Gruijter et al., 2006). The cost of sampling and analysis are such that it is difficult to obtain enough samples to accurately characterize the landscape variability. This economic consideration resulting in low sampling density has been recognized as a major limiting factor. Both proximal and remote sensing technologies have been implemented to provide highresolution data relevant to the soil attributes of interest. Remote sensing involves the deployment of sensor systems using airborne or satellite platforms. Proximal sensing requires the operation of the sensor at close range, or even in contact, with the soil being