Browsing by Subject "Vermehrung"

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    Generative sowie vegetative Vermehrung, Entwicklung, Morphologie und chemische Bekämpfung der windenden Unkrautarten: Calystegia sepium (L.) R. Br., Convolvulus arvensis L., Ipomoea hederacea Jacq., Ipomoea purpurea (L.) Roth und Fallopia convolvulus L.
    (2013) Willeke, Leonie; Gerhards, Roland
    Vining weed species as the two perennial plants Calystegia sepium and Convolvulus arvensis, and the annual species Ipomoea hederacea, Ipomoea purpurea and Fallopia convolvulus are very important in agriculture worldwide due to their high competitive ability. The aim of this work is to gain a better understanding of the morphology, physiology and reproduction of these species and the efficacy of herbicides on the weeds to develop improved control strategies with this knowledge. The first section of this paper consists of studies about the generative propagation and seed germination in response to various factors. It is shown that the species of the family of Convolvulaceae have morphological similarities and any weed species can germinate in a wide temperature range and in all studied soil types. The proliferation studies revealed that the rhizome and root pieces of Calystegia sepium and Convolvulus arvensis are dormant in the winter and sprout in spring. In addition, several buds on rhizome and root pieces also directly next to each other can sprout and the percentage of sprouting increases with the number of buds. Additionally, a negative linear relationship between the burial depth of the rhizome and root pieces in the soil and the ability to emerge is determined. In addition to these results, the analysis of the starch and sugar concentrations during a growth period shows that the starch concentration reaches its minimum 1.5 months before flowering. In the second part of this work, the main focus is placed on weed control with herbicides especially with the novel active substance TCM (Thiencarbazone-methyl), an acetolactate synthase (ALS) inhibitor, whose mechanism is investigated. The active ingredient TCM remains stable in the vining weeds and does not degrade as in corn. Proven TCM is absorbed through the leaves and transported systemically. TCM causes a disruption of the amino acid balance. The increase of the branched amino acids is carried out in dependence of the time as well as the applied herbicide concentration. TCM under greenhouse conditions as well as the active ingredients dicamba, glufosinate and glyphosate, frequently used in corn, control annual and perennial weed species germinated from seeds to a degree of more than 85% in the full and half field application rate. In comparison, the efficacy of shoot control of vegetatively propagated perennial plants is about 5-15% lower. Nevertheless, the regrowth of rhizome and root pieces is suppressed by the herbicide applications almost completely. The studies of the control in different growth stages show that the effect of TCM, dicamba and glyphosate on the annual species is greater in earlier stages of growth; however, the generatively propagated plants are controlled constantly even high in the later stages of growth. In contrast, with an increasing shoot length from 5 cm to 30 cm, the efficacy of control of the vegetatively propagated plants decreases to an average 40 %. The obtained control of Calystegia sepium and Convolvulus arvensis after a spring and a fall application under field conditions is much lower than under greenhouse conditions. Post-emergence application at recommended field application rates results in a reduction in the aboveground biomass of Calystegia sepium with TCM about 65% and of Convolvulus arvensis to a maximum of 50% with TCM, TCM in combination with TBT(tembotrione) and dicamba. The herbicides dont reduce the sprouting ability of underground organs of both species; and corn yield isnt even increased by the use of a herbicide against Convolvulus arvensis. Fallopia convolvulus, an annual species, is controlled in field trials by TCM and TCM in combination with TBT in the normal field application rate to an extent of more than 90 %, also with dicamba. The control results of Ipomoea hederacea in the two experimental years vary greatly. On average, the efficacy of the application of TCM in combination with IFT (isoxaflutole), glufosinate and dicamba in combination with diflufenzopyr is as high as in the greenhouse experiments with a rate of 95 %. In summary, the results show that young plants germinated from seeds in early growth stages can be controlled quite well above and below ground with the studied herbicides, so that TCM can be used to control Fallopia convolvulus as an alternative to other herbicides used conventionally. Despite the proven systemic translocation and inhibition of regrowth of rhizome and root pieces of vegetatively propagated perennial species TCM as well as the other tested herbicides do not provide suffcient long-term success of control of Calystegia sepium and Convolvulus arvensis in spring and in fall application under field conditions. The mechanical control of perennial species can be optimized by a strong division of the rhizome and root pieces in combination with a high burial depth.
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    How can miscanthus be integrated most efficiently into agricultural production systems?
    (2019) Mangold, Anja; Lewandowski, Iris
    The demand for biomass is increasing steadily, as fossil resources are gradually being replaced by biomass within the context of a developing bioeconomy. Plant-based feedstocks currently used for this replacement virtually all come from annual crops. However, perennial crops such as miscanthus are expected to be more environmentally benign due to their generally low-input requirements and high yield potential. Despite these advantages, the current cultivation area of miscanthus in Europe is quite low. One reason for this is that the cultivation and utilization of miscanthus faces several challenges. For example, the most common propagation method via rhizomes is very labour-intensive and thus expensive, leading to high establishment costs. Seed propagation is a promising option to reduce costs, but is not suitable for sterile genotypes. Another challenge to be overcome is the problem of re-integrating former miscanthus fields into crop rotations. The crop following miscanthus needs to be highly competitive in order not to be impaired by resprouting miscanthus shoots and thus able to achieve high yields. Additionally, there is only little information available on the effect of miscanthus cultivation and its subsequent removal on soil N content. This information is however crucial, for example to avoid environmental problems being caused by a potential nitrogen leaching after a miscanthus removal. If miscanthus is to be utilized as a biogas substrate, there are further challenges to be overcome. Firstly, the optimal harvest date needs to be defined with regard to the methane hectare yield and resilience of the crop to green cutting. Secondly, as a continuous supply of biomass throughout the year is necessary, ensiling will become a relevant topic. However, information is still required on the optimal harvest date to achieve a sufficient silage quality and the effects of ensiling on methane hectare yield. Finally, the suitability of miscanthus for biogas production is also influenced by biomass quality such as the proportions of leaf and stem. This has already been established for miscanthus utilization in combustion but has not yet been sufficiently investigated for anaerobic digestion. In summary, there are a number of uncertainties involved in miscanthus establishment, removal and utilization, which currently hamper its integration into agricultural production systems. From a bioeconomic point of view, this integration needs to be conducted as efficiently as possible in terms of nutrient-use, environmental and land-use efficiency. The aim of this study was to contribute to the filling of these knowledge gaps. To answer these knowledge gaps, several miscanthus field trials and laboratory experiments were conducted: a novel propagation method was tested; the re-integration of miscanthus fields into a crop rotation was analysed; and the effect of genotype, harvest date and ensiling on the digestibility and methane hectare yield was investigated. The results illustrate some possibilities of improving the nutrient-use, environmental and land-use efficiency of miscanthus biomass production along its supply chain: It was shown that miscanthus propagation via collars is feasible and a promising alternative to rhizome propagation, as the multiplication rate of collars is comparable to that of rhizome propagation. As the harvesting of collars is likely to be less labour-intensive and is less destructive for the mother field than rhizome propagation, this method is more favourable for both economic and ecological reasons. The re-integration of miscanthus into crop rotations revealed maize to be a suitable crop after miscanthus, as it coped with the prevailing soil conditions and suppressed resprouting miscanthus efficiently, resulting in satisfactory yields. The soil mineral nitrogen (Nmin) content was found to increase during the vegetation period following a miscanthus removal, but was generally on a low level (average: 17.3 kg Nmin ha-1). Additionally, it was found that, in Germany, miscanthus should be harvested in mid-October to maximize methane yields and nutrient recycling but minimize yield reduction. In addition, silage quality was best when miscanthus was harvested on this date. As leaf proportion correlated positively with substrate-specific methane yield (SMY) and thus genotypes with a higher leaf proportion were found to have a higher SMY, methane hectare yields could be increased even further by using genotypes with a high leaf proportion. In summary, the approaches developed in this study allow to considerably improve the ecological and economic performance of miscanthus production by increasing nutrient-use,environmental impact and land-use, and thus simplifying implementation into practice.
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    Saponin fractions from fenugreek (Trigonella foenum-graecum L.)as dietary supplements for Nile tilapia (Oreochromis niloticus L.)and common carp (Cyprinus carpio L.)
    (2012) Stadtlander, Timo; Focken, Ulfert
    The future role and importance of aquaculture for the world food supply is more and more recognized by the public. High quality feed for semi-intensive and intensive aquaculture operations are necessary to guarantee a future continuous growth of fish production. Nutrient utilization efficiency has in the past been augmented by addition of feed additives, mainly anti-biotics and hormones. That practice is prohibited in the European Union since 1st of January 2006 and the consumer acceptance of products produced in that way is low. Around a decade ago saponins, secondary plant metabolites, have been found to be potential alternatives for aquafeeds. Saponinmixtures derived from the South American soap bark tree Quillaja saponaria, have been found to have beneficial effects on growth, feed and nutrient utilization and on metabolism of common carp Cyprinus carpio and Nile tilapia Oreochromis niloticus. Furthermore, in one of the early experiments a sex ratio in favor of males was observed in saponin fed tilapia compared to control fish not supplemented with saponins. An influence on sex ratio of Nile tilapia would be highly desirable since industrially Nile tilapia production is only financially viable if all male populations are produced since mixed sex tilapia populations tend to reproduce uncontrollable. The production of all male tilapia populations is mainly conducted by feeding the potentially environmentally hazardous and carcinogenic synthetic hormone 17--methyltestosterone to sexually undeveloped tilapia fry. The above mentioned problems led to a joint research project with partners in Israel and Palestine in which this dissertation has been conducted. The aim of the project was the fractionation of crude saponin extract derived from fenugreek Trigonella foenum-graecum and its testing in vitro and in vivo. It was assumed that a higher biological activity could be achieved if saponin fractions instead of crude mixtures would be applied. After in vitro testing, different saponin fractions or eluates, have been tested on their effects on growth, feed and nutrient utilization, metabolism, proximate composition, gene expression of GH and IGF-1, sex ratio, reproduction and gonad histology. Most of the feeding experiments were conducted with Nile tilapia but one experiment was also conducted with carp. Three of the feeding experiments have been conducted in a system capable of measuring continuous respiration of the fish. Another experiment has been conducted at a field station at Jericho, Palestine. The experiments conducted to evaluate the influence of saponin fractions on sex ratio of undifferentiated tilapia fry have been conducted primarily in a flow-through system. The tested saponin fractions and a tested sapogenin are not suitable to produce male monosex tilapia populations. The sex ratios after supplementation of diets of mixed sexed tilapia fry did only in one case show a significantly higher proportion of males than the control. In a larger scale repetition of that experiment the previous observations could statistically not be proofed. It must be assumed to be random effects or be the result of initially biased sex ratios after stocking undifferentiated tilapia fry. An experiment in which genetically female tilapias were fed with two fenugreek saponin fractions and positive and negative controls supported that finding. A long term feeding experiment conducted at Jericho revealed no influence of the long and short term supplemented Q. saponaria saponin mixtures on sex ratio and reproduction of genetically female tilapia. A similar laboratory experiment with fenugreek saponin fractions could not be evaluated in that regard. The experiments evaluating the effects of the saponin fractions on growth, feed and nutrient utilization, gene expression of GH and IGF-1 and proximate composition revealed no significant differences. But in all experiments one fraction eluated with 60%/40% (v/v) methanol/water showed numerically improved values compared to control and other fractions. Furthermore one fraction eluated with 40%/60%/ (v/v) methanol/water gave constantly numerically inferior results of tested parameters compared to control. That supports the conclusion that the 40% methanol fraction contains saponins generally referred to as anti-nutrients. In only one experiment, conducted at Jericho, significantly higher growth was observed after long term supplementation with a Q. saponaria saponin mixture containing elevated sapogenin content. The presented data in this thesis is not supporting an application of the tested saponin fractions as environmentally friendly alternative to methyltestosterone to produce all male populations of tilapia or to inhibit uncontrollable reproduction. Additional experiments are needed to evaluate different modes of application like immersion treatments or injections since during the experimental work of this thesis all tested saponins were added to the feed. An application of the tested fenugreek saponin fractions as growth promoters yields a higher potential although the experimental results are based upon low sample sizes due to capacity restrictions of the respirometric system. Therefore a repetition under near commercial or commercial conditions must be considered.