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Effects of tillage systems on the seed bank persistence and seedling emergence of ten arable weeds
Summary
To test the effects of different tillage implements on soil seed bank decline and on seedling emergence, 5000 seeds m-2 of the arable weed species Avena fatua, Echinochloa crus-galli, Stellaria media, Spergula arvensis, Sinapis arvensis, Capsella bursa-pastoris, Raphanus raphanistrum, Thlaspi arvense, Solanum nigrum and Tripleurospermum perforatum were broadcast in experimental plots. The implements were the curry comb, the cultivator and the plough. After 25 months, the percentage of weed seeds recovered ranged from 0-12 %, depending on the species. The highest number of re-detected seeds was for Thlaspi arvense in soils under plough tillage. In contrast, no seeds were recovered from Spergula arvensis and Avena fatua. As there were no significant differences among the three treatments concerning the decline of the soil seed bank, seedling emergence in the curry comb and the cultivator plots significantly exceeded the values of the plots under plough tillage.
The impact of post harvest weed seed predation compared to stubble cultivation on weed seed decline
Summary
The complete article is written in German
Experiments were conducted in 2002 and 2003 to study the impact of weed seed losses due to predation without stubble cultivation and fatal germination after stubble cultivation between harvest of winter wheat and seeding of winter barley. In both years, defined numbers of seeds from different weed species and small annual grains where placed in plots on a winter wheat stubble and predation by birds, rodents and small organisms in the soil was determined. Additionally, the same amount of seeds were filled in flax bags and buried into the stubble after cultivation. Six weeks later, the number of viable and dormant seeds was counted. Weed seed decline caused by predators varied between 30 and 60 %. Small annual grains were almost completely fed by predators. In 2003 weed seed decline caused by predators was higher than by fatal germination after stubble cultivation. The results can be used to predict dynamics of weed populations under different tillage practices.
Effect of soil tillage intensity on seedbank dynamics of oilseed rape compared with plastic pellets as reference material
Summary
Tillage operations with different intensities following the input of oilseed rape seeds and an inert reference material (plastic pellets) resulted in seed banks which varied in size and vertical distribution. The size of the rapeseed bank has mainly to be attributed to seed losses in or on the soil, since seed bank and seed losses correlated with 0.84. Highest seed losses and consequently smallest soil seed banks were determined in treatments without stubble tillage and primary tillage by using a plough or a rigid tine cultivator in late autumn. A comparison with the reference material showed seed losses mainly in the soil horizon 0-10 cm (maximum seed: reference ratio 0.17) for treatments without stubble tillage, with non-inversion tillage operations or with zero tillage. A treatment with immediate, shallow incorporation of seeds and ploughing in late autumn resulted in seed losses mainly in soil horizons 10-20 cm and 20-30 cm (maximum seed: reference ratio 0.19). Several mortality factors e.g. predators or fatal germination seem to differently affect seeds depending on cultivation sequence and soil depth.
The study allows to divide the occurrence and vertical distribution of seeds in a soil seed bank into effects of mechanical shifting and into effects of seed mortality. The data will be integrated in models for seed bank dynamics of oilseed rape and weeds.
Predicting the potential geographical distribution of parasitic weeds, a contribution to risk management: case study of Orobanche crenata
Summary
The complete article is written in German
The potential distribution of the parasitic weed Orobanche crenata was studied in a combined literature, laboratory and simulation study. Populations of the root parasite only exist in regions with mediterranean climate, although individuals are able to reach maturity under conditions of temperate climate, too, and although O. crenata seeds can survive temperatures of -20 °C. The dormancy behaviour of its seeds is likely to impede the northward spread of this species, since in a continuously moist environment, hardly any dormancy release takes place. Results of sensitivity analyses using simulation models suggest that a change to warmer and/or drier climate would substantially increase the risk of O. crenata establishment at higher latitudes. The collected information can, particularly when combined with data on host crop production, contribute to parasitic weed risk management.
Distribution, importance and control of Bromus species in the Middle West of Germany
Summary
The complete article is written in German
Bromus species are important weeds in arable crops. Due to the increase of reduce tillage systems and larger areas of winter oilseed rape and winter wheat there is still a small increase of Bromus sp. However, even if the plough is used year by year occurrence of Bromus may not be avoided. Bromus sterilis is the most important species, but combination the other Bromus sp. can often be observed. The distribution in the field shows that Bromus is mainly a problem of the field margins. However, even all other possible distribution forms can also be observed. The coverage of the whole field is rare. In these cases often other reasons like contaminated crop seeds are involved. There are no regional borders for the occurrence of Bromus. Main arable regions showed a higher and regions with higher altitude above sea level showed a lower infestation with these weeds.
If a field is stronger infested farmers started with control activities. Management of field margins, intensification of stubble tillage (incl. use of glyphosate) and the additional use of selective gramicides are of importance. The use of special ALS-inhibitors for control of Bromus often is not as good as expected. More experience and recommendation are needed to improve the efficacy of these herbicides.
Weed and weed seed-bank response to tillage systems, straw and catch crops in continuous barley
Summary
Weed and weed seed-bank response to different tillage systems, straw and catch crops was investigated over the years 2000-2003 in a field trial with continuously grown barley. We found no effect of straw on weed density on the first two years of the experiment. Lower number of weeds in plots with straw was found on later years. Shallow loosening in spring, shallow catch crop incorporation in spring and no-tillage significantly increased weed infestation, compared to conventional deep plowing. No-tillage favored spread of Sonchus arvensis L. and Tripleurospermum perforatum L., but decreased the number of Chenopodium album L. Tillage systems had no effect on weed seed-bank. Straw incorporation decreased weed seed-bank, especially of Chenopodium album and, therefore, future weed infestation.
Pre-dispersal predation and seed damage of Centaurea scabiosa L. (Asteraceae)
Summary
Centaurea scabiosa L. (Asteraceae) is host plant of several Tephritidae (Diptera) species. They use flower heads for development and are the main predators of the seed. We studied the mechanism of fruit fly damage in number, weight and germination of the seeds.
Dominant species in C. scabiosa flower heads was Terellia colon (Terelliinae), which destroyed 11 % of seeds. Undamaged seeds from central flower heads were significantly lighter than in lateral flower heads.
Germination of the seeds was not significantly correlated with proportion of damaged seeds. However damage to flower head, significantly reduced weight of the remaining healthy seeds.
Development of weediness in different summer intercrop stands
Summary
The complete article is written in German
The influence of summer intercrops on weediness development was evaluated in central Bohemia in the years 2004-2005. The following species were sowed as intercrops after stubble tillage: Lolium multiflorum L., Lolium perenne L., Phacelia tanacetifolia Bentham, Brassica napus L., Sinapis alba L., Raphanus sativus L. var. oleiformis Pers., Lupinus albus L., Trifolium incarnatum L. and Trifolium subterraneum L. Stands of S. alba and B. napus were established also into the preceding crop stand before its harvest. Experimental plots had area of 40 m2 each. After sowing, dominance (%) and aboveground dry mass production (kg ha-1) of intercrops, weeds and volunteer wheat were evaluated continually. The highest degree of weed and volunteer cover was found at the end of the vegetation period in stands of L. albus and B. napus . Stands of S. alba and P. tanacetifolia Indicated a low weed cover. Volunteer cereals were almost eliminated by S. alba and P. tanacetifolia in 2005. Dry mass production of volunteers in B. napus stands was 158.5 and 586.4 kg ha-1 and 137.5 and 833.4 kg ha-1 in L. albus in 2004, and 2005 respectively. The influence of the year and the way of stubble tillage on weeds and volunteers was documented.
Influence of microorganisms on weed and crop seeds?
Summary
The complete article is written in German
The natural degradation of weed and crop seeds in soils takes place in the upper layer of the soil, mostly affected by aerob microorganisms or seed predating insects. Advancing the microbial processes by application of appropriate microorganisms could reduce the input of weed seeds into the soil seed bank and diminish the weed density in the following crop. In laboratory experiments soil born strains of Streptomyces and one white rot fungus were tested for their capability to deteriorate seeds of Brassica napus L. and Chenopodium album L. The effect was measured as weight loss and ligninase activity. The applied methods are discussed with regard to further experiments.
Biological decline of Solanum nigrum due to virus infections
Summary
Pot experiments were et up in order to study the effect of Pepino mosaic virus (PepMV), Óbuda pepper virus (ObPV) and mixed infections on Solanum nigrum. Virus infections significantly reduced biomass and seed production of S. nigrum plants. ObPV could cause more severe biological decline of S. nigrum, as compared to PepMV. Despite considerable reduction in the extent of germination, seed viability was not significantly influenced due to virus infections. Virus infections influenced rather characteristics of seed dormancy, than viability of seeds. Nitrogen (N), phosphorus (P) and potassium (K) content of S. nigrum leaves considerably inreased due to virus infections. Neither ObPV nor PepMV could be transmitted by S. nigrum seeds. Our results underline the fact, that plant viruses unfavourably influence physiological processes not only of the crops, but also of the weeds. Therefore, indirectly they may contribute to the reduction of a weed population.
Study of biomass production and growth dynamic of Bolboschoenus laticarpus nom. prov.
Summary
The weed Bolboschoenus laticarpus nom. prov. has recently spread in some localities on arable land in the Czech Republic. This originally wetland plant of the Cyperaceae family appears in maize, wide row crops and field vegetables. With regard to unknown causes of expansion, unknown biology and undocumented B. laticarpus reproduction on arable land, we focused on quantification of above- and belowground biomass production, as well as rhizomes and tuber production in model pot experiments. The observation of biomass production began at the beginning of vegetation season (April). One tuber was put in every pot and the experiment was evaluated monthly (from May to October). Furthermore, there was observed the influence of the length of vegetation period on biomass production (outplanting was carried out monthly from April to July).
Plants produced on average 97.0 g of aboveground biomass, 467.2 g of belowground biomass, 1556.8 cm of rhizomes and 145.0 tubers during vegetation season. Plants produced on average 25.0 (2004) and 43.8 (2005) new shoots during the vegetation season.german version
Weed studies on Hungarian lavender plantations
Summary
The paper describes the successional processes and stages of the weed vegetation of lavender (Lavandula angustifolia MILL.) plantations in the Transdanubian region (Hungary) comparing their species composition, diversity and physiognomical features. Using the Zurich-Montpellier methodology syntaxonomical relevés were taken in the sampled plantations. Data analysis was carried out by multivariate methods of SYNTAX 2000 software (PODANI 2001) or by MS Excel.
Weeds in Lavender plantations are controlled mechanically because herbicides would pollute the oil made from lavender. In the first 6-8 years, when shrubs of lavender are still small, hoeing may be performed more often (4-5 times each year). After 10-12 years shrubs reach a size that makes hoeing impossible becuase lavender shrubs are damaged: Therefore, only less effective methods can be applied. As a consequence, in the first period segetal weeds emerge, but after 10-12 years weed communities transform to ruderal associations.
Study of biomass production and population dynamic of Elytrigia repens in pot experiments
Summary
The perennial weed Elytrigia repens is the most important and widely spread in the Czech Republic. Increasing trend of occurrence of this weed on arable land since 1990 was caused mainly by minimal tillage, unsuitable crop rotations and by using non effective herbicides.
Pot experiments were conducted in the beginning of vegetation season in April 2004 and 2005. The length of rhizomes, weight of aboveground and belowground biomass, number of shoots and spikes were measured monthly. The highest increase of biomass was observed in July and August. One plant is able to product about 100 new aboveground shoots per vegetation season. From April to October 2005 plants produced an average of 8782.6 cm rhizome lenght. Average fresh aboveground biomass per plant was 95.4 g in 2004 and 116.3 g in 2005 and fresh belowground biomass was 162.9 g in 2004 and 295.2 g in 2005.
Plant temperature variation in the thermal weed control process
Summary
The technology of thermal weed control is based on heating plant tissues in high temperature media. The main rate which can evaluate the thermal effect for a weed in this technology is the plant tissue temperature, its alteration and time-exposure as well. Temperature measurement technique in plants and their media is proposed. Consistent patterns of temperature alterations in plants and their media in thermal weed control process are treated. Energetic and agro technologic evaluation of thermal weed control process is proposed.
Characteristics of development and nutrient uptake of Johnsohngrass ( Sorghum halepense (L.) Pers) growing from seed during the first year
Summary
The complete article is written in German
Johnsongrass is an adventive, serious weed of Hungary. Its vegetative and generative reproduction is successful.
The aim of the study of first year development and nutrient uptake of Johnsohngrass grown from seeds was that we can provide new data and further information to the knowledge of the biology of the S. halepense.
To study the biology of S. halepense a pot experiment with soil culture under greenhouse conditions was set up in the spring 2004. Samples were collected from June to November on regular basis in every month. During the vegetation period we have taken samples 6 times in all. During our work nutrient uptake (N, P, K, Ca) of Johnsongrass grown from seeds was examined in a whole growing season. During its first year the development of S. halepense can be characterised by intensive nutrient uptake and growth. Its nutrient (N, P, K) uptake remains intensive throughout the whole growing season. According to our examination S. halepense can uptake nitrogen, potassium and calcium in a great quantity.
Effect of herbicide MCPA on biological properties and second-generation productivity of weeds surviving in barley crop
Summary
The annual weeds Chenopodium album L. and Galium aparine L. sensitive and resistant, respectively to phenoxy acid compounds were used as the study objects. The effects of MCPA on biochemical changes and fertility of these species were investigated.
The obtained data showed that in the tissues of Ch. album sensitive to this herbicide, the content of the phytohormone IAA, zeatin and particularly ABA was reliably lower, and only traces of GA3 were found. In the tissues of G. aparine- resistant to MCPA, the content of zeatin and GA3 remained unchanged, while that of IAA was lower by 11 % and of ABA higher by 13 % as compared to control. MCPA exerted different effects on protein fund ESP and HSP fractions transformation. The results of the composition of protein fund, ESP and HSP fractions allow a suggestion that the features of sensitivity C. album L. and resistance G. aparine L. to MCPA, can be related to protein fund transformation and ensuring the stability of protein content and composition. In the year of MCPA spraying (1.0 l/ha), the damaged C. album ripened normally and developed seeds of higher viability. The second generation of the weed produced 34.8 % more seeds in comparison to plants unexposed to the herbicide. MCPA was found to stimulate the propagation of G. aparine already in the year of herbicide application. Therefore, the agrophytocenosis that was damaged by the herbicide MCPA naturally recovered in the following year.
Effect of different grazing systems on dynamics of grassland weedy species
Summary
The effect of different grazing regimes on dynamics of weedy species was studied in an upland grassland in the Jizerské Mountains. We applied continuous stocking and rotational grazing. The experiment included three replicate pairs of plots. Cover of the most abundant weedy species was estimated in 100 m2 permanent plots. Weedy vegetation varied as a result of time and differences between treatments. We revealed higher cover of broad-leaved dock (Rumex obtusifolius) and tall weedy grasses (Holcus mollis, Poa trivialis) under rotational grazing, whereas continuous grazing supported successively increase of dandelion (Taraxacum spp.). The results demonstrate that not only grazing itself but also different grazing system alters the composition of weedy vegetation in grasslands.
Weed population dynamics in integrated and organic cereal cropping systems
Summary
The complete article is written in German
Since 1995 a long-term trial at the experimental site „Dahnsdorf“ (Fläming, state of Brandenburg, Germany) comparing an integrated and an organic farming system is carried out. Hence, it is possible to quantify the long-term effects of different farming systems on weed population dynamics. Changes in weed density and species composition of weeds occurred only after approx. 5 years. By now, the weed emergence after continuous treatment with a 50 percent reduced rate of herbicides is about 50 percent higher compared with the situation-related dosage. This applied especially to Apera spica-venti and Matricaria spp. In the organic farming system an increase in the occurrence of Cirsium arvense and Vicia hirsuta was observed. Additionally, the diversity of weed species in the organic farming system is higher compared with the continuous treatment with a 50 percent reduced herbicide dosage.
The influence of temperature and light on seed germination of mugwort ( Artemisia vulgaris L.)
Summary
It has been discovered that mugwort can occasionally produce viable seeds also in Turkey. Therefore, the objective of this study was to determine the effects of temperature and light on germination of mugwort seeds collected from five different locations of Turkey. Experiments were conducted under nine constant temperatures, and three light conditions.
Germination of mugwort seeds was influenced from temperature, but almost independent from light conditions. The highest germination percentages were achieved at temperatures ranging from 15 to 30 °C. In general, lower and higher temperatures resulted in reduction of germination percentages, and germination was totally inhibited at 45 °C. Time (day) required for final germination percentage decreased progressively with increasing temperature. It was estimated that optimum germination temperature was approximately 29 °C for three Black Sea Region lots, 30 °C for Aegean lot, and 33 °C for Mediterranean lot. The optimum temperature for means of all seed lots (Turkey) was 29 °C. The results of this study are important to understand germination requirements of mugwort, allowing development and improvement of management strategies specific to mugwort.
Late emergence of weeds in maize
Summary
Recently weed seed content of soils in Hungary has increased dramatically. This leads to severe weed problems even at later growth stages of the crop plants. In this study late-emerging weed populations were surveyed and characterized in a site-specific manner at a 9.2 ha field. Furthermore their effect on maize and future crops was evaluated. At selected sampling sites weeds were removed manually at different phases of crop development, newly emerging weeds surveyed and seed production by the major weeds determined. An evaluation of the data showed, that weeds emerging at later stages of maize development do not necessarily reduce crop yield significantly. However, they may interfere with maize harvest efficiency and the weed seeds produced contribute significantly to the soil weed seed bank thereby increasing weed problems for future years or even decades.
Seed emergence dynamics and production of aboveground and belowground biomass of Taraxacum officinale L.
Summary
The emergence of Taraxacum officinale in pot experiments was observed in different depth of soil (surface, 0.5, 1.0, 2.0, 3.0, 4.0, 5.0 cm) in different substrate types: 1. river sand, 2. 1/3 topsoil + 1/3 river sand + 1/3 peat substrate, 3. topsoil (orthic luvisoil). The experiment was evaluated every day. The best emergence was from sand. The maximum soil depth for successful seed emergence in substrate 2 was 3.0 cm. In the next two experiments, 20 seeds were filled in each pot and later thinned to 1 plant per pot. The aboveground and belowground biomass and the length of taproot were observed. The first experiment was established in the beginning of vegetation (April) and was evaluated every month until the end of vegetation (October). From April to October 152.1 g of aboveground biomass, 109.5 g of belowground biomass, 22.2 cm long taproot and 36.2 mm diameter of root collar were produced. The other experiment was set up in April, May, June and July and was analyzed in the end of vegetation (October). Plants which were grown in June and evaluated in October produced an 18.4 cm long taproot. The experiment was carried out over 2 years in 2004 and 2005.
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