Development of a novel mechatronic system for mechanical weed ...

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Introduction techniques. It is known that some weeds are able to grow in soil conditions suboptimal or even unfavourable for crops, so a soil testing is necessary before the soil nutrient or pH can be improved or the crop selected. The relationship between soil structure and weed development is similar to that of nutrients, which means indirect impact. Optimal soil structure will not help the weeding, but pure structure, compaction and cultivation pans can lead to the spread of weeds via deep underground stems or roots, or could cause the appearance of waterlogged soil, preferable for some weed species. The choice of the crop should be based primarily on the soil type and climate. In cases where more options in the choice of cultivars exist, most desirable are species with rapid establishment, vigorous growth, prostrate – leafy types or long straw cereals. An increase in the sowing rate could result in an improvement of the crop’s competitiveness effect and provide compensation for the losses incurred during mechanical weed control (Parish 1990). Cultivation is of great importance in weed management and it should always be properly varied depending on needs of different crop and weed populations (Mohler and Galford 1997). Cultivation also provides many other beneficial effects far beyond the weeds. It is important for aerating the soil, stimulating crop root growth, conserving soil moisture and providing insulation with loose, dry soil mulch. To choose an adequate cultivation mechanism for optimum weed management, it is important to know the weed history of the field and to understand their lifecycle (Buhler 1995). Different weed species require different cultivation procedures. For example one successful method against perennials is weakening of the weed plant by separation of the above – ground and underground parts, which leads to exhaustion of the food reserves in the underground part. The most significant factors of annual weeds are conditions for their germination. Germination is dependent on the correct levels and mixture of moisture, oxygen, carbon dioxide, temperature and in some weeds the presence or absence of light. Combination of these conditions often causes seeds to have distinct germination periods, so well timed cultivation can drastically decrease the weed population. Crop seeds are usually larger and planted deeper then most weed seeds, which provides a possibility to calculate the cultivation depth, damaging just weed plants. A seedling is most vulnerable 12
Introduction from the time it germinates until after the plant has fully emerged from the soil. After the crop emerges the number of cultivations performed is usually relative to the weed pressure and limited by growth of the crop. In a well managed system two cultivation passes are required. The first pass is the most critical to exterminate the annual weeds, but the second pass is often necessary to eliminate the weeds that were stimulated to grow by the first cultivation. By a theoretical approach cultivation can be divided into primary and secondary cultivation, although the difference between them is often fuzzy. Usually, primary cultivation includes all operations which refer to initial land preparation such as subsoiling and ploughing, and also surface preparation during a fallow. On the other hand, secondary cultivation refers to operations designed to produce a seed bed after sufficient depth and fineness is reached by primary cultivation. From the point of view of weeding, the key aim of secondary cultivation is to keep the depth of cultivation within the germination depth of the weeds, which is for most small seeds maximally 5 cm (Schans et al 2006). Cultivation below this depth will bring up new viable seeds and should be avoided. There are also some techniques which encourage weed germination prior to crop germination, i.e. the first weed elimination can be done before the crop system is established. Two often-used methods are false seed beds and stale seed beds (Johnson and Mullinix 1995). The false seed bed technique involves a second pass to eliminate emerged weeds. This second pass is to be usually done with the same technique as the one that created the initial seed bed and it is ideal when a new seed bed is made in the same pass. A stale seed bed involves weed elimination without soil disturbance, by thermal weeding methods. Another weeding technique is blind harrowing, which is a hybrid between false and stale seed beds. A characteristic of this method is that the stale seed bed should be created first and then the crop drilled. Just a few days before the crop emergence a harrow, tine weeder or similar device is used to cultivate the soil surface to kill the weeds. 13
Page 1 and 2: Institut für Landtechnik der Rhein
Page 3 and 4: Development of a novel mechatronic
Page 5 and 6: Kurzfassung Entwicklung eines neuar
Page 7 and 8: Acknowledgements Acknowledgements M
Page 9 and 10: Table of contents Table of contents
Page 11 and 12: Glossary of abbreviations and symbo
Page 13 and 14: Symbol Unit Description Mmmax Nm Ma
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Page 17: ωold ωout rad s -2 Latest rotatio
Page 20 and 21: Introduction The most frequently us
Page 22 and 23: Introduction application that had p
Page 24 and 25: Introduction be to go from a system
Page 26 and 27: Introduction limited and environmen
Page 28 and 29: Introduction than 40 years before g
Page 32 and 33: Introduction Sowing and planting al
Page 34 and 35: Introduction Inter-row weeding syst
Page 36 and 37: Introduction 18 Figure 1.3 Inter-ro
Page 38 and 39: State of the art 20 Figure 2.1 a) F
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Page 48 and 49: Definition of the problem and resea
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Page 55 and 56: Materials and methods Figure 4.3 a)
Page 57 and 58: 4.1.2 Data acquisition 4.1.2.1 Hard
Page 59 and 60: 4.1.4 Test objects Materials and me
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Results and discussion 62 Figure 5.
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Results and discussion objects. Acc
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Results and discussion Plant positi
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Results and discussion Plant positi
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Results and discussion 70 5.1.4 Dis
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Results and discussion 72 Figure 5.
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Results and discussion Connection b
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Results and discussion 76 5.2.1 Opt
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Results and discussion xmi1 = ( RLA
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Results and discussion With the inv
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Results and discussion 82 Horizonta
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Results and discussion 84 5.2.4 Sel
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Results and discussion 86 5.2.5 Dis
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Results and discussion Conventional
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Results and discussion Since the fi
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Results and discussion To avoid con
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Results and discussion As the size
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Results and discussion 96 5.3.4 Alg
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Results and discussion 98 V = zc( t
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Results and discussion corresponds
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Results and discussion 102 5.3.6 Me
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Results and discussion hoeing accur
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Results and discussion between the
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Results and discussion distance fro
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Results and discussion Distribution
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Results and discussion cuts are ran
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Results and discussion Forward spee
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Results and discussion x [mm] Distr
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Results and discussion The experime
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6 Summary Summary Neither a mechani
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Summary The third part of the work
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7 Conclusions Conclusions The prese
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8 References References Agrios, G.
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References in California's Sacramen
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References Johnson, W C and Mullini
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References Schans, D. v. d. et al.
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List of figures List of figures Fig
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List of figures Figure 5.24 Scheme
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Plant position 9 Appendix Table 9.1
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Plant position Table 9.3 Detection
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Personal data Education About the a
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