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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.
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