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Изложены результаты исследований биотехно­логий выращивания сельскохозяйственных культур, а также сформулированы задачи инженерного обеспечения биоло- гизации земледелия и пути их решения.
The pollen stratigraphical and lithological data obtained from Lake Lasva, southern Estonia, are summarized. The land-use and vegetation history during the last 6300 years in an agricultural area with dense prehistoric setting is discussed. A high sedimentation rate and laminated structure of lake deposits enabled high-resolution palaeobotanical study of a 985 cm long core. Accelerator mass spectrometry ¹⁴C dates show good linearity and fit well with varve counts. Up to ca 2900 years BP, birch, pine, spruce and broad-leaved species, later mostly birch, pine and alder, grew in that area. The first weak signs of human impact were traced at 6300 years BP. Human activities were more pronounced between 5400–5100 and 3800–3500 years ago, due to the foundation of Neolithic settlements not far from the lake. The first attempt of small-scale tillage, detected from the first finds of Triticum pollen, followed by a long-term gap, dates back to 5100 years BP. Crop cultivation (Cannabis, Hordeum, Triticum and Secale) became the main means of subsistence not until the Iron Age at about 1600–1400 years ago, but extensive arable farming started to develop 800 years ago, after the German crusaders invaded the area. Pollen diagrams display several setbacks in arable farming, mostly caused by crop failure due to climate deterioration and decrease in the population caused by famines, wars and epidemics.
Vapour pressure deficit, in addition to light and temperature, is the main meteorological element that influences the degree of transpiration rate, which in turn determines the impact of drought stress on the yield of onions. In this study we attempt to assess the effect of vapour pressure deficit on onion cultivation in Poland and present a temporal and spatial distribution of vapour pressure deficit for the years 1966–2005. During the period “end of emergence–harvest” (Ee–H), vapour pressure deficit had the greatest impact on onion yield in central western Poland and in the Sandomierz Basin (south east). In these regions the average total yield of onion was 15% lower than the long-term average for the entire country, and yields lower than the long-term average occurred every 1–2 years. A statistically significant year-to-year increase in vapour pressure deficit during the Ee-H period indicates the possibility of a further increases in the risk to onion cultivation.
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