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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 36 (1996), S. 0 
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The dynamics of seed populations of Avena sterilis ssp. ludoviciana (Durieu) Nyman in plots maintained under different crop rotations and tillage systems was studied over a 5-year period. The seed reserves buried in the soil were practically depleted during this period by using any of the three cropping systems evaluated. No significant differences were found between using a continuous barley rotation with annual application of herbicides and using a barley:fallow rotation with herbicides applied only as needed. The decline in seed populations was not affected by the tiliage system used during the fallow period (ploughing or no tillage). The tillage practices used in the various treatments, combined with the variable seed output from each treatment, resulted in different vertical distribution of the seeds in the soil profile. Shallow cultivation resulted in an accumulation of seeds in the upper soil layers; in contrast, a large proportion of the seeds were buried and maintained below 15 cm in the ploughed treatments. Although the seed distribution patterns produced by the various tillage systems had an effect on seedling recruitment, the largest changes in this parameter were associated with the different cropping sequences. Four times more seedlings were recruited in years under barley cropping than in those under fallow.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: For implementation of simple yield loss models into threshold-based weed management systems, a thorough validation is needed over a great diversity of sites. Yield losses by competition wsth Sinapis alba L. (white mustard) as a model weed, were studied in 12 experiments in sugar beet (Beta vulgaris L.) and in 11 experiments in spring wheat (Triticum aestivum L.). Most data sets were heller described by a model based on the relative leaf area of the weed than by a hyperbolic model based on weed density. This leaf area model accounted for (part of) the effect of different emerging times of the S. alba whereas the density model did not. A parameter that allows the maximum yield loss to be smaller than 100% was mostly not needed to describe the effects of weed competition. The parameter that denotes the competitiveness of the weed species with respect to the crop decreased the later the relative leaf area of the mustard was determined. This decrease could be estimated from the differences in relative growth rate of the leaf area of crop and S. alba. However, the accuracy of this estimation was poor. The parameter value of the leaf area model varied considerably between sites and years. The results strongly suggest that the predictive ability of the leaf area model needs to be improved before it can be applied in weed management systems. Such improvement would require additional information about effects of abiotic factors on plant development and morphology and the definition of a time window for predictions with an acceptable level of error.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 35 (1995), S. 0 
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Seed populations of Avena sterilis ssp. ludoviciana (Durieu) Nyman were monitored in a naturally occurring infestation throughout its life cycle. Considering the large weed population present (298panicles m−2), total seed production was relatively low: 3838 seeds m−2. Only 68% of these seeds were recovered from the soil surface and a further 3% were removed with wheat grain and straw during harvest operations. The numbers of seeds from the stubble between mid-July and mid-September were relatively low (10%). Ploughing the stubble in October buried most of the recently produced seed rain and resulted in a relatively uniform vertical distribution of the seedbank. Maximum seed persistence in the soil ranged from 27 to 43 months (depending on the experimental technique used to do the study). Seed decline followed an exponential pattern on a yearly basis, with the greatest decline taking place between October and April (57–90% in year 1 and 10–40% in year 2), Between May and September the buried seed populations remained practically constant. Seedbank depletion was primarily due to seedling production (25%) and ‘lethal’ germination (24%). Although the depth of burial had very little effect on seed survival, the mode of seed disappearance was closely related to their depth in the soil. Seed depletion through ‘lethal’ germination increased with increasing depth in the soil, whereas depletion through seedling emergence decreased with increasing depth.
    Type of Medium: Electronic Resource
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