Browsing by Subject "Weed"

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Die Auswirkungen einer einmalig variierten Bodenbearbeitung auf Ertragsbildung, Verunkrautung und Bodennitratgehalt unter ökologischen Produktionsbedingungen
(2007) Häberle, Annette; Claupein, Wilhelm
Although organic farming is a very non-polluting kind of agriculture, nitrate leachate losses can also be found under this management. Restrictions in organic fertilization have the purpose to keep the nitrate leachate with soil tillage and crop rotation on a low level. Due to this aim field experiments were conducted to investigate the short-term effect of timing and method of cultivation after the harvest of legumes and crops with high-N crop residues on N mineralization, nitrate leaching, crop growth, diseases and weeds in wheat crops. The study was designed to compare the effects of the ?Schutz- und Ausgleichsverordnung? (SchALVO) in Baden-Württemberg and tillage strategies which are normally used in practice, like reduced and conventional tillage in autumn and to compare different times of conventional tillage in winter and spring in three different areas of Baden-Württemberg with typically soil types. The areas were located in the Main-Tauber-Kreis with soils from Keuper and shell lime, in the Gäu-Region with soils from löss and the Schwäbische Alb with soils of limestone. Especially organic farms use, for the admancement of yield und for the regulation of weed population, a timely and increased requirement of soil tillage. In the results of October 2002 till summer 2005 there was no significant influence of timing and method of cultivation, for example reduced tillage in autumn or tillage in winter or spring, on the productivity of organic farms. In the most cases the conditions on the experimental fields were very good resulting of a low weed density and a good farming management. On fields with a high density of perennial weeds the risk of multiplication of weed population persists even after a short-term variation of tillage. There were only a few, not significant differences in the development of wheat growth because of different soil tillage. The most differences were seen between the growth of winter wheat and summer wheat. The yield of summer wheat was not significantly lower than the yield of winter wheat. Summer wheat reached nearly the same yield potential with higher amounts of crude protein. Especially in areas with strong winters and low N-input the yield of summer wheat was higher than the yield of winter wheat. Because of a second peak of mineralization in spring there was a better adaptation of NO3-release to the growth of summer wheat after soil tillage in November, December and February. Because of the better utilization of soil-N from summer wheat the lower yield potential in comparison to winter wheat was relativised in the most areas. With regard to N mineralization a time displacement of soil tillage in winter or spring didnt reduce the N-mineralization before winter in all cases. But in this time displaced treatments there was a second peak in N-mineralization additional to the first peak in autumn. Short-term practice of reduced soil tillage did not reduce N-release in the field experiments. Altogether a time displaced soil tillage in winter or spring could be, based on the experiments, a practical alternative for N-conservation through winter with regard to N-mineralization as well as with regard to corn yield. With the cultivation of a fast-growing catch crop farmers could reach an additional reduction of mineralised N amount over winter. In the farming practice a well timed sowing of catch crops is not always possible, like it is shown in the experiments, but it should be kept in mind for N conservation.
Cover cropping in integrated weed management
(2018) Sturm, Dominic; Gerhards, Roland
Weed control constitutes a major challenge in the worldwide crop production. Beside chemical and mechanical weed control strategies, cover cropping provides an effective way of biological weed suppression. Five different field experiments were conducted at six locations from 2014-2016 to evaluate the weed control efficacy of different cover crops in mono and mixed cultivation combined with different fertilization strategies and sowing dates. Furthermore weed suppressing effects of cover crop mulches in spring and of living mulches in summer were investigated. Potential effects on sugar beet emergence, quality and quantity were also assessed. In three laboratory and two greenhouse experiments from 2015-2017, the proportional contribution of competitive and biochemical effects on the overall weed suppression and the identification of varying susceptibilities of different weeds against biochemical stresses were at the center of research. In field experiments, the weed suppressive effects of cover crops and living mulches in mono and mixed cultivation were tested. The experiments emphasized the importance of cover crop and living mulch mixtures compared to mono cropping due to a higher flexibility to biotic and abiotic stresses. This was followed by a more constant biomass production and more effective weed suppression. Moreover, the observed weed control was a result of competitive and biochemical effects, induced by cover crops. These were later on analyzed for active weed growth suppressing compounds. Altering cover crop sowing date and fertilization to optimize the weed control resulted in significant changes of cover crop and weed biomass. Early cover crop sowing five or three weeks before winter wheat harvest increased the weed control efficacy in one year, significantly. Due to contrary results over the two experimental years, we suggest that the cover crop biomass and consequently the weed suppressive ability depends on sufficient soil water for rapid cover crop germination and growth. The use of cover crop mulch in sugar beet crops provided a weed suppression of up to 83%. Especially mulch derived from cover crop mixtures reduced the weed density (56%) more effectively compared to mono cultivated cover crops (31%). The inclusion of cover crops, mulches and living mulches can lead to significant herbicide reductions in the main crop. However supplementary mechanical or chemical weed control strategies are still necessary, especially in crops with a low competitive ability like sugar beets. Nevertheless, novel mechanical weed control approaches and adequate herbicide application techniques, as band-spraying, can reduce the herbicide input in the long-term. Germination tests with aqueous cover crop extracts were conducted on weed seeds to evaluate differences in the inhibition of germination and root growth. Furthermore, different sensitivities of the weeds against the different cover crop extracts were revealed. Some cover crops as S. alba, F. esculentum, H. annuus, T. subterraneum and L. usitatissimum showed the most effective weed suppression. Moreover, the weed M. chamomilla showed the highest susceptibility against biochemical stresses in the germination tests. A strong positive correlation between the weed suppressive effects by the extracts and the field weed suppression was found. This indicated that biochemical effects play also an important role on the overall weed suppression in the field. To estimate the proportions of competitive and biochemical effects on the overall weed suppression by cover crops, greenhouse experiments with active carbon supplemented soil were conducted. These experiments revealed that biochemical effects, by the presence of active carbon in the soil, shifted the balance of competition between cover crops and weeds. In the course of the experiments, we also found species-specific effects on the donor as well as on the receiver side. The results of this thesis demonstrate the diverse use of cover crops, their mulches and living mulches in agricultural systems. This work aims on the optimization of biological weed control strategies and indicates approaches for future research. It is for example not yet clear how cover crops suppress specific weeds and if it is possible to design combinations of specific cover crops for the suppression of individual weed communities. Additionally, these results help to reduce long-term herbicide inputs in agricultural systems.
Integrated management, analysis of mechanisms and early detection of resistant populations of Alopecurus myosuroides HUDS. and Apera spica-venti L. Beauv.
(2015) Kaiser, Yasmin; Gerhards, Roland
The control of pests is one of the major challenges in agricultural production worldwide. Especially weeds cause severe yield losses by competing with crops for light, space, water and nutrients. Due to the relatively low costs for acquisition and application of herbicides and a high control efficacy, chemical measures are predominantly applied to control weeds. In Europe, Alopecurus myosuroides HUDS. (blackgrass) and Apera spica-venti L. Beauv. (silky windgrass) are major weeds especially in winter wheat. The occurrence at high population densities in combination with a consequent use of herbicides with the same modes of action has resulted in the selection of resistant populations. Populations with target-site resistance (TSR) as well as non-target-site resistance (NTSR) could be confirmed for A. myosuroides and A. spica-venti. In contrast to the mechanisms of TSR, NTSR mechanisms are less investigated. Due to the steadily increasing number of putative herbicide resistant weed populations, the demand for rapid resistance tests is rising. The papers of the dissertation focus on the integrated management, the investigation of resistance mechanisms and the detection of herbicide resistant weed populations. The following research objectives have been examined within the four work packages (papers): – To develop a new methodology for a rapid detection of herbicide resistance and to confirm that results are comparable with classical greenhouse approaches – To investigate metabolism of herbicides in sensitive and resistant populations of A. myosuroides to gain comprehensive knowledge on resistance mechanisms – To evaluate the influence of agronomic factors on the probability of resistance occurrence and to develop a geo-referenced database for mapping the spread of herbicide-resistant A. spica-venti populations across Europe – To assess the influence of crop rotation and herbicide strategies on population development and herbicide resistance of A. myosuroides and crop yield The four papers come to the following results regarding the main research objectives: 1st paper: A laboratory test was developed to accelerate the detection of herbicide resistance. Therefore, A. myosuroides was cultivated in wellplates containing nutrient agar and herbicides. The evaluation of herbicide resistance was conducted by a sensor, measuring chlorophyll fluorescence. The results of the developed test corresponded well to the standard whole-plant pot tests in the greenhouse. In both tests sensitive and resistant populations were identified, however results of the Chlorophyll Fluorescence Imaging were available earlier. 2nd paper: Metabolism of herbicides was investigated in populations of A. myosuroides by using liquid chromatography - tandem mass spectrometry (LC-MS/MS) to gain comprehensive knowledge on mechanisms of herbicide resistance. NTSR populations differed from sensitive and TSR A. myosuroides in form of an enhanced degradation of the active ingredient or metabolite, depending on the investigated herbicide. For the investigated herbicides (inhibition of ACCase and ALS) it was shown that herbicide metabolism plays an important role regarding herbicide resistance in A. myosuroides. 3rd paper: To evaluate the influence of agronomic factors on the probability of resistance occurrence in A. spica-venti, numerous populations were screened in the greenhouse. The corresponding field history obtained from questionnaires and the results of greenhouse assays were used to develop a GIS-database in which herbicide-resistant A. spica-venti populations were mapped. The statistical analysis revealed that a high percentage of winter crops in the crop rotation, together with conservation tillage, early sowing dates and high population density increased the occurrence of herbicide resistance in A. spica-venti. 4th paper: To assess the impact of crop rotation and herbicide strategies on A. myosuroides, field studies at two locations in Southern Germany have been carried out. Results show that densities of A. myosuroides increased in continuous winter wheat. The introduction of spring crops significantly reduced densities, even without using herbicides. Furthermore it has been shown that the risk of herbicide resistance was reduced when performing a consequent change of herbicide mode of action. The use of herbicides with only one mode of action increased the number of herbicide resistant plants. Crop yield was notably influenced by A. myosuroides in winter wheat. The overall results of this dissertation showed the great impact of agricultural measures on herbicide resistance in A. myosuroides and A. spica-venti and demonstrated opportunities for prevention and management. The developed resistance quick test provides an accelerated detection of herbicide resistance and therefore the chance to initiate resistance management strategies much earlier.
Interactions of farming and plant biodiversity in weed control related ecosystem service provision and weed conservation
(2020) Schumacher, Matthias; Gerhards, Roland
There is evidence that diverse plant communities in terrestrial ecosystems are either more stable or more productive in terms of food web support and ecosystem service provision. In agro-ecosystems, characterized by high disturbance and external inputs, plant diversity and their services can only be provided by weeds. In the first study, vegetation recordings and farmer surveys were conducted in on-farm experiments in two regions of Southwestern Germany. The aim was to examine the effects of agricultural management on weed community composition, weed biodiversity and occurrence of rare arable weed species in cereal fields. Weed biodiversity was influenced mainly by crop species, herbicide use and farming system as well as nitrogen and light availability. Weed communities were quite similar in both study regions and dominated by Alopecurus myosuroides, Galium aparine, Viola arvensis, Polygonum convolvulus and Veronica persica. A redundancy analysis revealed that the weed community was mainly shaped by crop species, tillage, location in the field and timing of herbicide application. The results highlight the erosion of weed communities due to intensive agricultural practices and emphasize the conservation of weed biodiversity per se and rare arable weed species in particular. The next aim was to examine if this biodiversity is able to support weed control related ecosystem services, like the predation of weed seeds. The objectives of this study were to investigate the connection between weed biodiversity, Carabid beetle diversity and weed seed predation as well to evaluate the role of farming intensity in this sequence. For this purpose, on-farm experiments were performed on the Eastern Swabian Alb. A positive correlation between weed biodiversity and Carabid beetle diversity was identified as well as a pattern of medium Carabid beetle diversity providing the highest weed seed predation. There was no consistent influence of farming intensity on weed seed predation. The revealed connection between weed diversity, Carabid beetle diversity and weed seed predation highlights the role of plants in food web support and subsequent ecosystem service provision. The utilization of these services depends on the promotion of biodiversity by designing appropriate management strategies. In the next step, the general principles underlying ecosystem service provision by biodiversity, were conveyed to a cover cropping system. The aim was to test single sown cover crops and species mixtures in terms of weed suppression efficacy and reliability. For this purpose, cover crop species were sown singly and as mixtures in a field experiment. Lower weed dry matter and weed densities were found predominantly in treatments with favorable establishment and above-average biomass production. Mixtures performed much more homogeneous in regard to the measured parameters compared to single sown cover crops. The results suggest that, although particular single sown cover crops are more effective to control weeds than mixtures, mixtures are more reliable under changing conditions. Altering the species composition of cover crop mixtures according to more complementary traits might further improve their weed control efficacy. The results of this dissertation demonstrate the importance of plant biodiversity in the provision and reliability of weed control related ecosystem services, either by weeds themselves or by specifically designed cover crop mixtures. Furthermore, management factors influencing weed biodiversity were determined, which can aid in the creation of more sustainable management strategies for a diverse agroecosystem and the conservation of rare arable weed species.
Lentil production in Germany : testing different mixed cropping systems, sowing dates and weed controls
(2012) Wang, Lina; Claupein, Wilhelm
As a kind of legume crop, lentils (Lens culinaris Medik.) with their high nutritional value are grown mainly for human consumption in many regions of the world. The crop has benefits in crop rotation due to its symbiotic N-fixation, which is important especially in organic farming, and it can also increase crop biodiversity in arable land. In Europe, lentils are considered one of the popular leguminous food crops. However, the cultivation and scientific research on lentils were neglected in Germany and Central Europe over the past 50 years. Recently, farmers have begun to realize the value of lentils and have re-introduced the crop into organic and conventional farming in Central Europe. The lentil plant has a weak stalk and is easily lodging. Lodging plants cannot be completely cut and picked up by combine harvesters, and result in yield loss, especially under the wet conditions that often occur in Central Europe. To avoid lodging of crop, lentils were commonly grown in mixed cropping with cereals, such as oat (Avena sativa L.), barley (Hordeum vulgare L.) and rye (Secale cereale L.). However, there is little current information on lentil cultivation under temperate climates in this region. One of the most relevant challenges for growing lentil is how to explore its yield potential adapt to the local conditions. Moreover, lentil plant has a low competition capacity against weeds which are always one of the big agronomic problems especially on organic farm. Therefore, three field experiments presented in this dissertation were carried out to design and improve lentil cropping systems under organic farming in Germany in terms of productivity and competitiveness performance, suitable species and proportion of companion crops, lentil cultivars, sowing dates, weed control, and seed quality. The results should be used to adapt lentil cropping systems to different local climatic conditions in Germany. The specific objectives were (i) to optimize lentil-based mixed cropping systems through different combinations of companion crops (barley, wheat (Triticum aestivum L.), oat, linseed (Linum usitatissimum L.) and buckwheat (Fagopyrum esculentum Moench)) and mixing ratios, which were expected to show different performance on crop productivity, weed infestation, and lentil lodging, (ii) to determine whether different sowing time (early, medium, late) have effects on a standard lentil-barley mixed cropping system in regard to crop yield and weed control, (iii) to test whether woodchip mulch can help suppressing weeds and increasing crop yield in lentil monocropping and mixed cropping, (iv) to determine whether different mixing ratios affect seed protein content in lentil-cereals (barley, wheat) mixed cropping system. To achieve the first objective, a two-year field experiment of mixed cropping of lentils with five spring-sown companion crops: naked-barley, wheat, oats, linseed and buckwheat was conducted at the organic research station Kleinhohenheim in 2009 and 2010. Besides sole lentil and sole companion crops, three mixing ratios (3:1, 1:1, 1:3) were used. Lentil grain yield was 1.47 t ha-1 in monocropping and 0.58-1.07 t ha-1 in mixed cropping, depending on the mixing ratio and companion crop (Chapter 2). The land equivalent ratio (LER) was higher in mixed cropping than in monocropping generally. Lentil-wheat and lentil-barley mixed cropping with a ratio of 3:1 resulted in the highest LER (ca. 1.50) whereas lentil-linseed had the lowest LER in all ratios. Lowest lodging was observed in lentil-wheat and lentil-oat mixed cropping. Additionally, mixed cropping with ratios of 3:1, 1:1 and 1:3 (lentil: companion crop) reduced weed biomass by 29 %, 41 % and 24 %, respectively, compared with lentil monocropping. The results indicated that lentil mixed cropping in the study seemed more promising than monocropping under the given conditions of the location. Except for the linseed, all tested species can be well used as companion crops especially the two cereals (barley and wheat) which can be recommended. The mixing ratio should consider the total yield advantage (LER), the risk of crop lodging, and marketing considerations of both crops. To achieve the second objective of the study, another two-year (2009-2010) field trial was carried out at two sites: the organic research station Kleinhohenheim (KH) and the conventional research station Oberer Lindenhof (OLI) (Chapter 3). The crop was sown at three dates (early, medium and late) in the period from March to May. Four genotypes of lentil: Anicia, Schwarze Linse, Hellerlinse and Berglinse were mixed-cropped with naked-barley at a ratio of 3:1 (lentil:barley) at each sowing date. Results showed that grain yield of crops was significantly higher at the earliest sowing both for lentils (3.0 t ha-1 at KH, 2.4 t ha-1 at OLI) and barley (1.2 t ha-1 at KH, 2.6 t ha-1 at OLI). Lentil seed per plant, barley seed per ear, and thousand kernel weight of crops decreased significantly with delayed sowing. At KH experimental site, weed biomass increased significantly with delayed sowing and was independent of the lentil genotype, whereas sowing date had no significant effect on overall weed biomass production at OLI. The results indicated that early sowing can increase the yield of lentils, and can also be used as an indirect method of weed control in organic farming. To further control weeds to achieve the third objective, a field experiment of applying woodchips mulch on lentils was carried out at the organic research station Kleinhohenheim, in the years 2009 and 2010 (Chapter 4). Two years on average, an amount of 160 m3 ha-1 (fresh matter) woodchips mulch reduced weed biomass and weed density in both cropping systems compared to no mulch treatment, with a reduction by 43 % and 29 % (sole), and by 51 % and 30 % (mixed) respectively. Mixed cropping of lentils with barley (3:1) also decreased weed biomass compared with lentil sole cropping; however, no effect on weed density was observed. Lentil grain yield from sole and mixed cropping was 3.0-3.4 t ha-1 and 2.1-2.2 t ha-1 (2009), and 1.0-1.1 t ha-1 and 0.8-0.9 t ha-1 (2010). Barley grain yield was 1.4 t ha-1 in 2009 and 0.7 t ha-1 in 2010. Despite decreasing weeds, the mulch did not improve crops grain yields in mixed or sole cropping. The combination of woodchip mulch and mixed cropping is useful to reduce weed infestation in cropping systems where chemical or mechanical weed control is not possible and for crops with a low capacity for competition against weeds. Another focus of the study was on seed quality (protein content), especially for the cereals (Chapter 5). The two mixed cropping systems: lentil-wheat and lentil-barley with five seeding ratios (4:0, 3:1, 1:1, 1:3, 0:4) were tested at the organic research station Kleinhohenheim in 2009 and 2010 (originated from the experiment 1). Results showed that cereal grain protein increased significantly when their proportion was reduced in the mixture with lentils. Wheat crude protein increased from 10.3 % (2009) and 11.0 % (2010) in monocropping to 11.5 % (2009) and 15.1 % (2010) in mixed cropping with 75 % lentils. Barley crude protein increased in the same way from 13.7 % in monocropping to 15.8 % in mixed cropping with 75 % lentils. However, lentil protein content did not differ significantly across all mixing ratios. Total crude protein in a mixture was significantly higher than that in cereals or lentils monocropping. Mixed cropping with lentils can thus be an option to obtain a high protein content of wheat which is important for a suitable breadmaking quality, particularly in organic farming. Summarizing, the overall results of the study will open new options for growing lentils in Central Europe from where the crop has vanished over the last decades and may guide the future of lentil production in multi-cropping.