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On Farm Research (OFR) – a novel experimental design for Precision Farming
Summary
The complete article is written in German
OFR-Experiments represent an extension and completion to the classical field trial. The differences consist particulary in the necessity to include the heterogeneity of crop growth within the field. OFR allows evaluating procedures and algorithms for site-specific farming. The experiments will be carried out on practical fields. Due to the requirement of large data, the fields need to have a certain size depending upon the factors tested. The experimental design, monitoring and evaluation should be planned by trained engineers. The treatments within the experiment can be realized by the farmers with their own technology. Thus the experiments are relativley economical and adapted to the farmers requirements.
Site specific weed control as a part of the reduction program chemical plant protection
Summary
The complete article is written in German
From 1999 to 2005, long-term experiments in winter cereals with site specific weed control showed a significant reduction in herbicide use by post-emergence application. The method represents a minimising strategy in the context of chemical weed control. Site specific weed control accomplishes the demands and objectives of the German reduction program for chemical plant protection. Subject to groups of weed species and single weed species, 70 to 85 % of arable fields remained untreated with herbicides in specific years. In average, over a period of 7 years a herbicide reduction of 50 % could be estimated. There were no yield differences between treated and untreated areas.
Autonomous robots for weed control
Summary
The complete article is written in German
The development of sensor and actuator components for weed control has been improved in the last years. However, a complete autonomous field robot with all necessary functions is not yet available. Based on the previous works of the authors with the sensor-based cycloid how “Querhacke” and the autonomous vehicle optoMAIZER for the Field Robot Event a new concept for the modular autonomous robot Weedy for weed control within row cultures is proposed. The development steps include: sensor for crop detection, actuator for weed control, row guidance, U-turn, vehicle and system technology and application aspects.
Camera-guided weed control – a technology for practice
Summary
The complete article is written in German
A technology of site-specific weed control using digital image analysis and georeferenced application maps has been applied since 2004 in cereals, rape, maize and sugar beet. For camera-guided weed sampling, bi-spectral cameras took well focused grey scale images with a strong contrast of crops and weeds. For the identification of weed species, characteristic shape features of plants were calculated and compared with a database. With an identification rate from 73 % (malt barley) up to 77 % (sugar beets) application maps were created from classified images for site-specific weed control. Site-specific herbicide application was performed using a GPS-controlled patch sprayer with three separated hydraulic circuits. Herbicide savings ranged from 22 % to 70 % for grass weed species and from 4 % to 80 % for broadleaf weed species. Average savings of site-specific weed control were 27.30 €/ha. Therefore, calculated costs of 16.26 €/ha for camera-guided weed sampling and site-specific weed control using a three-chambered patch sprayer were compensated.
Image analysis for automatic classification of Rumex obtusifolius in mixed grassland swards
Summary
The complete article is written in German
Recent developments in site-specific weed control in arable crops are using digital image analysis for plant species identification. In grassland, these techniques have rarely been applied so far. The presented investigation deals with the development of methods for automatic weed detection in grassland based on digital RGB images. The focus was to detect Rumex obtusifolius (RUMOB) and other accompanying herbs, like Plantago major (PLAMA) and Taraxacum officinale (TAROF). 24 bit RGB images were transformed to 8 bit intensities. Based on that the local homogeneity was calculated from which a binary image was derived. Morphological opening was applied finally. The result was, that leaves of the weeds could be segmented from the image background. For each of object colour, texture and geometry features were calculated. Based on these features a Maximum-likelihood Estimation (MLE) was calculated in order to classify the objects into the classes (i) RUMOB, PLAMA, TAROF, soil, residue und (ii) RUMOB und residue. The average RUMOB detection rates ranged from 70,9 % to 95,3 %.
Abundance- and dispersiondynamics of weeds under sensor-based herbicide application within a spring barley field
Summary
The complete article is written in German
Within a spring barley field in two successive years variable rates of herbicides were applied in real time with a sensor operated field sprayer. Grid sampling was conducted along a 24 m x 50 m sampling grid. The two weed species Stellaria media L. and Polygonium convolvulus L. were most abundant. The average Jaccard number of 0.5 showed that between the two years the species composition at the sampling points was different. The relative frequency of the two main species at the sampling points was for black bindweed 26 % (2002), 63 % (2003) and for common chickweed 59 % (2002) and 19 % (2003).
The dispersion of the weeds between the two years was different. The analysis of the spatial covariance between the sensor values of 2002 and 2003 showed that there was no spatial dependence of the weed occurrence between the two years.
Evaluation of sampling and interpolation methods used for weed mapping
Summary
Weed mapping was carried out on 3 fields in central Bohemia in order to characterize the spatial structure and temporal stability of weed populations over six years (1999-2004). A rectangular grid 40 x 40 m or 20 x 40 m respectively was established applying GPS (Global Positioning System) along the wheel tracks on trial fields. The number of plants for each species and the total weed coverage has been recorded at the grid points. The resulting weed map is strongly affected by the sampling intensity and by the interpolation method used. This paper evaluates the quality of weed maps created using different sampling grids and sample sizes and compares recently used interpolation methods (Ordinary Point Kriging and Inverse Distance Weighting (IDW)). Sample size was found to be critical, particularly for weed species having low economic thresholds such as Galium aparine L. Kriging produced smoothed maps, when a spherical variogram model was used, IDW resulted in artificial contours with spots around the grid points if the setting of Power = 2 were used.
GIS-based analysis of sampling methods for site-specific weed control
Summary
The complete article is written in German
Manual sampling methods are still important for site-specific weed control albeit promising image-processing online methods are already available for this purpose. A diversity of different sampling methods for weeds from dense to relatively sparse sampling grid resolutions with varying sampling areas are described in literature. The main objective of this study was to determine the quality of these weed samples in order to create instructions for an adequate sampling method applying a custom-built geoinformation software. Using this software it is possible to determine the precision of a sampling method statistically and visually because weed distribution maps are produced for each sampling method. The results of an analysis which was based on high-resolution datasets of weeds spatial distribution in a simulated arable field will be presented.
Influence of application with low drift nozzles on the efficacy of herbicide treatments
Summary
The complete article is written in German
The potential impact of spray nozzle technology on effectiveness of herbicides was tested under field conditions at 24 test sites between 2002 and 2005. Various herbicides registered in cereals and sugar beet were employed. The results showed no significant influence of nozzle technology on the efficacy of herbicide treatments. Air induction nozzles with a size of 03 or 04 achieved regularly good or even excellent results in controlling broad leaf weeds and weed grasses in early growth stages.
According to these results the use of air induction nozzles with drift reduction of 50 % or 75 % can be absolutely recommended for the application of herbicides. This modern nozzle technology therefore contributes to environmental beneficial use of herbicides.
Geostatistical analysis of spatial heterogenity of Ambrosia artemisiifolia on Hungarian acid sandy soil
Summary
Exact weed definition can significantly modify the technology of weed control. The detrimental effects of herbicides on the environment appear predominantly on sandy soils with low organic material content. We defined the sample territories involved in the research in the northeastern region of Hungary, where the current problem of weed control is caused by the significant spread of the Ambrosia artemisiifolia . For the purpose of precision weed control, in addition to the traditional method of weed survey, we made snapshots with a broadband multispectral digital camera with sub metric accuracy, combined with a DGPS instrument, and then we prepared the weed map of the sample territory. Besides the weed survey, we studied the nutriment utilization of the soil and its physical composition. We compared the data of the ground measurements and remote sensing data of the Landsat images taken and processed for the sample territory. The exact recognition of the differences arising from the territorial heterogeneity enables the planning of more precise weed maps and plant protection interventions.
Identification of weeds in remote-sensed images on the basis of differences in spectral reflectance
Summary
The complete article is written in German
Site-specific weed control requires precise information on the spatial distribution of weeds in arable fields. The time and effort for a manual detection of weeds in this context is disproportionately high, hence new strategies are in demand which apply modern sensor-based approaches to achieve the required information. The application of remote-sensing for this purpose is the up-and-coming strategy. In this study a remote-sensing dataset from high-resolution optical sensor QuickBird has been used in order to detect weed species within a sugar beet field. A Ground truth dataset gathered applying the WeedScanner technique could be used to interpret spectral reflectance in the satellite images. Out of 4 selected different weed species only Canada thistle plants (Cirsium arvense L.) could be reliably distinguished between crop and soil. The main reasons for this were the typical spectral reflectance and the significant patchiness of this weed. Smaller weed patches (< 2.0 m diameter) could not be distinguished adequately with the mentioned satellite sensor.
Model experiment for optimising the number of weed survey sample areas
Summary
Weed surveys on agricultural fields deliver important information on the species’ composition, extent and frequency of occurrence in the field. Actual research work is especially important to plan weed control technology, forecast weed infestation and establish the input system of site-specific weed control.
Earlier studies carried out in 2002 proved that we would get enough information about the field’s weed cover if surveys were done on sample areas 2x2 m in size in regular arrangement on 0.5 hectares each.
To prove this hypothesis we set up an experiment in the spring 2005 in a winter wheat field, where we staked 1251 sample areas of 2x2 m in size on a field part of 0.5 hectares. The counting frames were placed side by side in 9 columns and 139 rows.
Weed survey was done in every counting frame with the method of Balázs-Ujvárosi, a method similar to Braun-Blanquet scale, which is widely used in Hungary for estimating weed cover.
Based on field data we concluded that the dominating weed was volunteer sunflower followed by Cannabis sativa, Papaver rhoeas and Sisymbrium sophia with average covers of 99.8 %, 99.8 %, 88.4 %, 69.8 % respectively. Galium aparine was only registered on 4 sample areas.
Experiments proved that weed density per 0.5 hectare large sample areas would be adequate if winter wheat field’s weed survey data of at least 2 years were available.
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