| 1. |
- Anbari, Saghi, et al.
(författare)
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Effects of root fragmentation on generative reproduction of Sonchus arvensis
- 2016
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Ingår i: Acta Agriculturae Scandinavica, Section B - Soil and Plant Science. - : Informa UK Limited. - 0906-4710 .- 1651-1913. ; 66, s. 391-398
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Tidskriftsartikel (refereegranskat)abstract
- To develop better mechanical management strategies, more information on the impact of root partitioning on generative reproduction of Sonchus arvensis L. is needed. Therefore, an outdoor experiment was performed in Sweden in 2008, to evaluate the effect of root fragmentation on generative reproduction of S. arvensis. Two artificial populations of S. arvensis with the same total root length per area but with different initial root lengths and different numbers of root fragments were planted. Cumulative numbers of flower receptacles which had shed mature seeds over the season were assessed. Changes in the number of seeds per flower receptacle and average seed weight were monitored over time during the late season. Plants from long root fragments produced more flower receptacles than plants from short ones. Per area, however, the number of mature flower receptacles did not differ. The number of seeds per flower receptacle and individual seed weight were not affected by initial root length for the first cohort of shoots which sprouted from the initially planted roots. A second cohort, from roots produced during the season, resulted, irrespective of its initial root length, in fewer flower receptacles per plant and per area, with less seeds per receptacle, but with the same average seed weight as the first cohort. The number of seeds per flower receptacle was higher in mid-September than earlier or later. Average seed weight slightly decreased over time. The weight of seeds produced in early September was inversely related to the number of seeds per receptacle, but this trade-off disappeared over time. Root fragmentation alone in pure populations of S. arvensis does not impede generative reproduction, but is likely to decrease input of seeds to the seed bank, when combined with crop competition.
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| 2. |
- Anbari, Saghi, et al.
(författare)
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Population dynamics and nitrogen allocation of Sonchus arvensis L. in relation to initial root size
- 2016
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Ingår i: Acta Agriculturae Scandinavica, Section B - Soil and Plant Science. - : Informa UK Limited. - 0906-4710 .- 1651-1913. ; 66, s. 75-84
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Tidskriftsartikel (refereegranskat)abstract
- To develop better mechanical management strategies, more information on the impact of root partitioning on changes in the population dynamics of Sonchus arvensis is needed. Therefore, the effects of root fragmentation of S. arvensis on shoot height frequency distributions, biomass production and nitrogen allocation were studied in an outdoor experiment in Sweden in 2008. Three artificial populations of S. arvensis of different initial root lengths but with the same total root length per area were planted. Shoot heights were measured at the onset of flowering and dry weight and nitrogen content of leaves, stems, buds and roots were quantified twice during the season. Height frequency distributions of the populations were bimodal, indicating the existence of two generations distinctly different in height growth pattern. Shorter root fragments produced shoots with a lower mean height compared to longer fragments. Plants originating from longer root fragments had higher dry weight and more nitrogen compared to plants from shorter root fragments. Dry matter production per square meter did not differ between the populations. The proportion of dry matter and nitrogen allocated to the different plant components (leaves, stems, buds and roots) at harvest did not differ between the populations. Over time, nitrogen was reallocated from leaves and stems to roots. Our results show that initial root length of S. arvensis per square meter, rather than the number of root fragments per square meter, is a good predictor of biomass at harvest, and that the degree of root fragmentation does not affect nitrogen allocation patterns. Root fragmentation, however, leads to a lower average canopy height for S. arvensis, and thus may be an effective weed control measure in combination with a crop which is competitive for light.
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| 3. |
- Anbari, Saghi, et al.
(författare)
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Sprouting and shoot development of Sonchus arvensis in relation to initial root size
- 2011
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Ingår i: Weed Research. - : Wiley. - 0043-1737 .- 1365-3180. ; 51, s. 142-150
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Tidskriftsartikel (refereegranskat)abstract
- To assess the effects of initial root size of Sonchus arvensis on sprouting and shoot development, an outdoor box experiment was performed in Sweden in 2008. Shoot emergence time, shoot numbers, rosette size and flower production were quantified as functions of root length and weight. Emergence of the first shoot per root and of later cohorts was delayed with decreasing root length and weight. Number of shoots per root increased with root length and weight, but per unit root length and weight, short roots produced more shoots. The first emerging rosettes were, for rosettes of a given age, larger for longer roots. Total rosette area per root 5 weeks after planting increased with increasing root length and weight. The number of flowers and production of mature seeds were positively related to root length and weight, because of delayed sprouting of short and light roots. The proportion of flowers leading to mature seeds declined with shoot emergence time. By clarifying relationships between root size and growth parameters, this study showed that fragmenting of S. arvensis roots delays phenological development and hampers reproduction by seeds. The information may be used to refine mechanical weed control strategies for S. arvensis.
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| 4. |
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| 5. |
- Delin, Sofia, et al.
(författare)
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Optimal Placement of Meat Bone Meal Pellets to Spring Oats
- 2018
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Ingår i: Frontiers in sustainable food systems. - : Frontiers Media SA. - 2571-581X. ; 2
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Tidskriftsartikel (refereegranskat)abstract
- New technology makes it possible to apply organic fertilizers with higher precision, and organic producers want to know how to exploit these new possibilities to make their production more efficient. This study investigated the effect of band application (in different positions) of pelleted organic fertilizer, compared with broadcasting, on grain yield and weed density in spring oats (Avena sativa L.). Six microplot field experiments were carried out on silty clay and sandy loam in Sweden during the growing season of 2014-2016. In oats seeded at 25 cm row spacing, pelleted meat bone meal was band-applied at one of three distances from the crop row (0, 4, and 12.5 cm) and at two or three incorporation depths (1 and 4 cm on silty clay and 1, 4, and 6 cm on loamy sand). These treatments were compared with broadcast spreading, mineral nitrogen fertilizer, and an unfertilized control. On both soil types, fertilizer placement 4 cm from the crop and 4-6 cm incorporation depth gave the highest yield and crop nitrogen uptake. Yield in this treatment was 800 kg ha(-1) higher on clay soil and 1,100 kg ha(-1) higher on sandy loam compared with the same organic fertilizer applied by broadcasting, an 80-150% yield increase. On the sandy loam, distance from the crop row had a more significant effect on grain yield (p < 0.001) than soil incorporation depth (p = 0.07). On the silty clay, crop yield was significantly influenced by incorporation depth (p = 0.003) and distance from the crop row (p = 0.04). In five experiments, mineral N fertilizer equivalent (MFE) increased from on average 63% with broadcasting to 85% with placement 4 cm from the crop row and 4 cm incorporation depth. Weed biomass was significantly affected by fertilizer placement on the clay soil, with higher weed biomass with deeper incorporation (p = 0.045) and greater distance from the crop row (p = 0.049). On the sandy loam, there was a tendency for larger weed plants at greater distance from the crop row (p = 0.13) except when seeds and pellets were placed together, which gave the highest weed weight, probably due to lower competition from the crop in this treatment.
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| 6. |
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| 7. |
- Delin, Sofia, et al.
(författare)
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Pelleterad organisk gödsel - mylla och placera nära såraden
- 2017
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Forskare vid SLU undersöker i pågående försök hur skörden påverkas av att placera pelleterad organisk gödsel på olika avstånd från såraden och att mylla den till olika djup. Preliminära resultat i havre visar att placering fyra centimeter från raden och fyra centimeters myllningsdjup gav störst skörd.
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| 8. |
- Eckersten, Henrik, et al.
(författare)
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Comparison of monocultures of perennial sow-thistle and spring barley in estimated shoot radiation-use and nitrogen-uptake efficiencies
- 2010
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Ingår i: Acta Agriculturae Scandinavica, Section B - Soil and Plant Science. - : Informa UK Limited. - 0906-4710 .- 1651-1913. ; 60, s. 126-135
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Tidskriftsartikel (refereegranskat)abstract
- Shoot radiation-use efficiency (RUE) and nitrogen-uptake efficiency (UPE) of monocultures of perennial sow-thistle (Sonchus arvensis L.) and spring barley (Hordeum distichon L.) were quantified to assess the significance of these traits for the relative performance of the two species. RUE and UPE were derived for shoot growth and N uptake by calibrating a mechanistic model to above-ground biomass and N observations in an outdoor box experiment, conducted during two years at two soil nitrogen levels in Central Sweden. The model, which is driven by climate variables, predicts above-ground biomass and nitrogen increment as a function of intercepted radiation, temperature, and nitrogen availability. Observed values of leaf area and root development are used as input. Shoot RUE in S. arvensis was only 56% of the RUE in spring barley (1.35 and 2.40 g dry weight MJ-1, respectively). On the other hand, shoot UPE in S. arvensis at low N supply during early season was seven times higher than in barley (0.07 and 0.01 d-1, respectively). For S. arvensis, UPE was higher at the low soil nitrogen level than at high level, while the reverse was found for barley, at a given amount of biomass per area unit. We suggest that the higher shoot UPE in S. arvensis at low nitrogen supply, in comparison with the low UPE of annual small grain crops at low soil nitrogen levels, is a contributing cause for the observed increase in S. arvensis in organic farming.
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| 9. |
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| 10. |
- Eckersten, Henrik, et al.
(författare)
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Modelling species competition in mixtures of perennial sow-thistle and spring barley based on shoot radiation use efficiency
- 2011
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Ingår i: Acta Agriculturae Scandinavica, Section B - Soil and Plant Science. - : Informa UK Limited. - 0906-4710 .- 1651-1913. ; 61, s. 739-746
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Tidskriftsartikel (refereegranskat)abstract
- Perennial sow-thistle (Sonchus arvensis L.) may be a serious weed in organic and conventional farming. To assess the effects of radiation acquisition and resource allocation on competitive ability, S. arvensis was grown together with spring barley (Hordeum distichon L.) in six mixtures in a replacement series with initial above-ground biomass proportions of S. arvensis ranging from 2% to 96%. A one-season experiment was made outdoors in boxes in Uppsala, Sweden, at a low level of nitrogen supply (5 g N m(-2)). The study tested the predictability of shoot biomass of each species based on two principal assumptions: (i) growth model parameters derived from species in monocultures could be applied in mixtures, and (ii) radiation in the mixed stand was partitioned between species proportional to their leaf area. Calibration of two parameters, for scaling of shoot radiation use efficiency and radiation partitioning respectively, were the base for the evaluation. When the coefficients were close to unity, which was the case for all mixtures dominated by barley, and for one of the mixtures with high proportion of S. arvensis in the early season, observed and predicted shoot biomass coincided well. For the evenly composed mixtures, total shoot biomass was underestimated (the scaling coefficient of shoot radiation use efficiency was > 1), whereas the relative composition among species was predicted well. In the late season the principal model assumptions were not applicable to S. arvensis, likely due to increasing root allocation not accounted for in the model. Sonchus arvensis in mixtures with high proportions was planted early in relation to sowing of barley, which resulted in a comparably late development stage of S. arvensis. Consequently the relation between species development stages varied with species composition suggesting a need to introduce effects of differences in development stage into the model.
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