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Plant-specific herbicide application requires sensor systems for plant recognition and differentiation. A literature review reveals a lack of sensor systems capable of recognizing small weeds in early stages of development (in the two- or four-leaf stage) and crop plants, of making spraying decisions in real time and, in addition, are that are inexpensive and ready for practical use in sprayers. The system described in this work is based on free cascadable and programmable true-color sensors for real-time recognition and identification of individual weed and crop plants. The application of this type of sensor is suitable for municipal areas and farmland with and without crops to perform the site-specific application of herbicides. Initially, databases with reflection properties of plants, natural and artificial backgrounds were created. Crop and weed plants should be recognized by the use of mathematical algorithms and decision models based on these data. They include the characteristic color spectrum, as well as the reflectance characteristics of unvegetated areas and areas with organic material. The CIE-Lab color-space was chosen for color matching because it contains information not only about coloration (a- and b-channel), but also about luminance (L-channel), thus increasing accuracy. Four different decision making algorithms based on different parameters are explained: (i) color similarity (ΔE); (ii) color similarity split in ΔL, Δa and Δb; (iii) a virtual channel ‘d’ and (iv) statistical distribution of the differences of reflection backgrounds and plants. Afterwards, the detection success of the recognition system is described. Furthermore, the minimum weed/plant coverage of the measuring spot was calculated by a mathematical model. Plants with a size of 1–5% of the spot can be recognized, and weeds in the two-leaf stage can be identified with a measuring spot size of 5 cm. By choosing a decision model previously, the detection quality can be increased. Depending on the characteristics of the background, different models are suitable. Finally, the results of field trials on municipal areas (with models of plants), winter wheat fields (with artificial plants) and grassland (with dock) are shown. In each experimental variant, objects and weeds could be recognized.

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.

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.

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.

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

Direct injection systems for Plant Protection Products (PPP) are developed to increase precision in application, to prevent the operator from contact with the chemical agents and to protect the environment against harm. They can be divided by the point where the PPP is injected in the pipes. These injection points cause different volumes of spray mixture in the piping system and therewith different response times until the desired spray mixture exits the nozzle. For sensor-based application, a short response time of the sprayer and variable rate application of different active ingredients are necessary.

The objective of this research was to develop a non-invasive yield mapping system for sugar beets by applying ultra wideband (UWB) radar technology. Similar to radars used in geological engineering, these devices acquire data via electromagnetic waves. The basic idea was to use such data to identify sugar beets in agricultural soils. The initial research task was to distinguish sugar beets from the surrounding soil.

The aim of this study was to optimize a direct injection system for real-time site specific herbicide application. From previous investigation conducted at the Institute of Agriculture Engineering in Bonn only the injection close to the nozzle orifice enables preparing the mixture fast enough. According to process flow the system was investigated in two separate parts: injection system, and transport and mixing system. In order to reduce the response time of the injection system, design optimization of injection device is needed. However, the control process represents the main optimization potential of the injection system. Hence, the injection system was optimized and new control process has been developed and tested.

The automotive industry increasingly uses natural fibres for interior parts. The components concerned usually do not have load functions, but dimensional stability must be guaranteed for parts of greater extension. Natural fibres are required to fulfil the demands of sufficient strength, low weight, and heat resistance. The advantage of using composites reinforced by natural fibres is considered to lie in their biodegradability and in the prospect of using them in environmentally friendly recycling techniques.