Browsing by Person "Kunz, Christoph"

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Integrated weed control in sugar beet (Beta vulgaris), using precision farming technologies and cover cropping
(2017) Kunz, Christoph; Gerhards, Roland
Weed control is one of the major challenges in sugar beet (Beta vulgaris) production worldwide. Due to the high flexibility and low costs, herbicide applications are the common agricultural practice for successful weed control. Yet, due to European and national restrictions, farmers are forced to substitute their herbicide input in order to reduce the chemical influence on the environment. Beside chemical weed control systems, integrated weed management (IWM), can be an alternative, to reduce the chemical preponderance. The five essential parts in composing a successful IWM system are: i) cover crops (CC) and ii) resulting mulch residues which can decrease the weed infestation prior to the actual crop establishment, iii) living mulches which can suppress weeds during the crop growth period and iv) precision mechanical weed control which can provide herbicide reductions. Last but not least v) herbicide applications should be optimized with sensor technologies to identify and reduce stress on crops. In the current study, all the named aspects of IWM were examined in sugar beets. In order to accomplish that, the following research objectives were investigated and answered in the course of the papers composing this thesis: • Evaluation of the suitability of CC and CC mixtures for weed suppression prior to sugar beet sowing • Assessment of differences in sugar beet emergence, weed control and biomass under different CC mulches • Application of living mulches and measurement of their weed control efficacy during the sugar beet growth period • Evaluation of mechanical weed control along with chemical band spraying compared to an overall herbicide application • Determination of the weed control efficacy of mechanical weeding by using visual sensors and GNSS-RTK • Investigation of the feasibility of intra-row mechanical weed control, its prerequisites and limitations • Detection of responses to herbicides by using chlorophyll fluorescence imaging technology 1st paper: Field and laboratory experiments were conducted to investigate the competitive and biochemical weed suppressive ability of CC. Applied aqueous CC extracts in germination tests inhibited weed growth and potential allelochemicals were identified. In the field all CC either in mixture- or mono-cultivation were able to suppress weeds compared to an untreated control by 66%. In the 2nd and 3rd paper sugar beet plant emergence was investigated in greenhouse and field experiments, in order to evaluate the influence of various CC mulches on weed suppression. Different CC mulches reduced weed germination successfully. During one dry growing season sugar beet emergence was enhanced by increased soil moisture due to the existence of a CC mulch layer compared to uncovered soil. Our findings suggest that CC mulch layers can substantially effect crop and weed development within the field. To assess the weed suppressive ability of living mulches in sugar beets, field studies were carried out at four sites in southern Germany, presented in the 4th paper. Results show that living mulches can reduce the total amount of different weed species in the inter-row area up to 71%. The white sugar yield was increased in average by 42% with the existence of living mulch as compared to the untreated control. In the 5th, 6th and 7th paper sensor technologies were used for mechanical weed control combined with chemical band application to reduce the herbicide input, with similar weed control results to the overall chemical application. Sensor based, mechanical precision steering technologies, reduced weeds more effectively than when compared to manual operator guidance. This is due to accurate fast driving speeds close to the crop area. Intra row elements (finger weeder, rotary harrow, torsion weeder, heap element) for mechanical weed control showed effective weed suppression. Nevertheless, suitable soil and weather conditions for mechanical weed control were not always given, which can result in an efficacy loss. Finally, in the 8th paper, a portable sensor, based on chlorophyll fluorescence imaging, was used in greenhouse experiments to investigate the response of plants after herbicide application. Various active ingredients have shown different damage concerning the photosystem II. The use of this sensor can quantify phytotoxic effects due to herbicides and can help to find the most suitable herbicide application date, active ingredients or herbicide mixture. The overall result of this dissertation reveals the great potential of CC, living mulches, precision mechanical methods and sensor technologies as part of an IWM system in sugar beet production.