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Sirvi Autor "Talgre, Liina (advisor)" järgi

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  • Pisipilt
    Kirje
    The effect of cover crops on biomass and nitrogen accumulation and on crop yield
    (Eesti Maaülikool, 2021) Toom, Merili; Lauringson, Enn (advisor); Talgre, Liina (advisor); Mäe, Andres (advisor); Bogužas, Vaclovas (opponent)
    The aims of the thesis were to evaluate the biomass and N accumulation of winter cover crop species (winter rye, winter turnip rape, forage radish, berseem clover and hairy vetch), winter hardiness of hairy vetch, the effect of sowing date on biomass and N accumulation and the effect of CCs on the yield of subsequent spring barley. The results showed that CC biomass and N accumulation depended on species and growing conditions, especially the sum of effective temperatures. Frost sensitive forage radish accumulated the highest amount of biomass and N in autumn, whereas berseem clover accumulated low amount of biomass and N, especially in the year with drought conditions before the establishment. Hairy vetch over-wintered similarly to winter turnip rape and winter rye in all trial years. Hairy vetch and winter turnip rape accumulated higher amount of biomass and N in the spring than winter rye, which may be partly related to characteristics of the used winter rye variety. Cover crop biomass and N accumulation decreased with delayed sowing dates, while the influence of sowing date on cover crop species was different. Forage radish produced the highest amount of biomass and N at all sowing dates. Although the biomass of rye was relatively low, the reduction at delayed sowing dates was lowest compared to other species. Among over-wintering CCs, hairy vetch as a legume species accumulated the highest amount of N in the spring. It can be concluded that in Estonia, CCs require sowing in early August to enable maximum biomass and N accumulation. It is possible to delay the sowing of over-wintering species if the following cash crop is sown later. As an average over the three years, only forage radish and hairy vetch significantly increased the yield of subsequent barley, probably because of the N contribution. None of the CCs had negative effect on barley, as the yield level following winter turnip rape, winter rye, and berseem clover were similar to the control.
  • Pisipilt
    Kirje
    Weeds in different cropping systems
    (Estonian University of Life Sciences, 2025) Madsen, Helena; Talgre, Liina (advisor); Luik, Anne (advisor); Institute of Agricultural and Environmental Sciences; Romaneckas, Kęstutis (opponent)
    ABSTRACT. Weeds play multiple roles in an agroecosystem. On the one hand they compete with crops for water and nutrients and on the other hand they enhance biodiversity within the field community, thereby providing environmental benefits. The aim of this study was to investigate weed occurrence in a long-term crop rotation experiment. The five-field rotation (barley undersown with clover, clover, winter wheat, pea, potato) was conducted under five different cropping systems. In two conventional systems herbicides were used for weed control, one of them also used mineral fertilizers. One organic system followed the crop rotation as a control variant. The remaining two systems used winter cover crops; composted manure was additionally applied to one of the systems. Weed occurrence and species composition depended on both the cropping system and the crop. In the first rotation the study of weed seedbank in the soil revealed that the number of weed seeds in organic cropping remained at a similar level compared to conventional systems, but species diversity was higher in organic systems. The highest number of weed seeds was found in the soil of pea fields across all systems except in organic system with winter cover crops. The lowest seed count was found in the soil of barley undersown with clover fields in conventional system with mineral fertilizers and in organic system with manure. In the second rotation, studies showed that weed biomass and density of occurrence was increased in all cropping systems, but significantly more in organic systems than in conventional ones. Also, weed diversity increased more in organic systems, being highest in the organic system with winter cover crops. Among the crops, weed biomass and density were high in pea and low in barley. Among the winter cover crops winter rye suppressed weeds most. However, likely due to their low biomass, winter cover crops did not achieve weed suppression comparable to herbicides. Nevertheless, winter cover crops improved soil properties and had a yield-enhancing effect.