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Most significant growing manner tool to gain high seed yield is the understanding about influence of different factors that have important role on winter oilseed rape growing. The lack of knowledge and research on different agro-ecological factors about oilseed rape growing is observed in Latvia. The aim of our research, started in the season of 2007/2008 and continued up to the season of 2010/2011 in Research and Study farm "Vecauce" of Latvia University of Agriculture, was to investigate the influence of agro-ecological factors (sowing date and rate, and fungicide as growth regulator) on seed yield of two types of winter rape cultivars. The observed seed yield results are analyzed in this paper. Rape was sown on five dates, starting with 1 August with ten days intervals. Specific four sowing rates were used in years 2007/2008 and 2008/2009: 120, 100, 80, and 60 germinate able seeds per m² for 'Californium' (line) and 80, 60, 40 and 20 germinate able seeds per m² for 'Excalibur' (hybrid). Equal sowing rates for both varieties were used in 2009/2010 and 2010/2011: from 120 to 20 germinate able seeds per m² with interval of 20 seeds per m². Fungicide as growth regulator (Juventus 90 s.c. (metconazole, 90 g L-1) dose: 0.5 L ha-1) was applied for rape plants at 4-6 leaves stage for crop sown on first three sowing dates. The highest average yield from all trial years was observed for variety 'Californium' sown on 10 August, and for variety 'Excalibur' F1 - sown on 20 August. Winter oilseed rape seed yield was significantly (p<0.05) affected by sowing date. The influence of sowing rate on yield was variable. Fungicide application significantly (p<0.05) increased the seed yield of 'Californium' in all trial years, but yield of 'Excalibur' - in three out of four trial years: 2008, 2010 and 2011. [ABSTRACT FROM AUTHOR]

Chemical composition of crops before winter is important for successful overwintering of plants. The aim of the research, carried out from 2007/2008 till 2009/2010 at the Research and Study farm 'Vecauce', was to investigate the influence of agricultural practices (sowing date, sowing rate, and fungicide application) and meteorological conditions during winter on the content of sugar in apical bud and root of two types of winter oilseed rape (Brassica napus L.) cultivars. The content of sugars (monosaccharides) in apical bud and root in autumn and following spring was analysed using the Luff-Schoorl method. Sugar content in apical bud and root of winter oilseed rape in autumn and spring differed depending on the trial year, because of different, even contrary (in season 2009/2010), meteorological conditions. Sugar content was higher in plant parts developed when rape was sown on earlier sowing dates, but it was substantially influenced by the sowing date only on some occasions. Sowing rate had no impact on sugar content in apical bud and root. Application of a fungicide as a growth regulator had no significant impact on the result, but sugar content decrease during winter 2009/2010 in the root of winter oilseed rape was smaller when fungicide as growth regulator was applied. [ABSTRACT FROM AUTHOR]

Lack of data about effect of meteorological conditions, sowing date, sowing rate, fungicide as growth regulator application and other agroecological factors on rape autumn growth is observed in Latvia. The aim of our research, started in autumn 2007 and continued up to autumn 2010 in Research and Study farm 'Vecauce', was to investigate the influence of agroecological factors (sowing date, sowing rate and fungicide (as growth regulator in autumn)) application as well as meteorological conditions on autumn plant growth of two types of winter rape varieties. Winter rape biometrical parameters were estimated, and meteorological parameters (hydrothermal coefficient (HTC) and growing degree days (GDD)) were calculated. Four year results showed that winter oilseed rape seed germination was affected by precipitation and air temperature around the sowing time. Calculated GDD correlated with plant biometrical parameters during trial years. HTC showed moisture effect on rape emergence time. Sowing date was important factor which had strong and significant impact on biometrical parameters of rape plants in autumn. Earlier sowing date increased height of growth point, root neck diameter, plant and root mass, and main root length significantly for both cultivars in four trial years. Such agro-ecological factor as sowing rate (plant density) affected plant biometrical parameters only in some trial years. Plant weight was significantly influenced by sowing rate for both cultivars if sowing rates were equal. Other important parameter - height of growth point - was not significantly influenced by sowing rate for both cultivars when similar sowing rates were used in all years; exception was year 2009 for 'Californium'. [ABSTRACT FROM AUTHOR]

Winter rape (Brassica napus L.) significance among field crops is unchangeable for last decade in Latvia. Rape plant development in autumn, plant wintering and plant yielding is partly influenced by plant density. The aim of our research, started in autumn 2007 in the Research and Study farm "Vecauce", was to investigate the influence of agroecological factors (sowing date, sowing rate and fungicide (as growth regulator in autumn) application) on two type (line and F1) winter rape varieties' plant density in autumn, in spring and at harvesting. Plant density in autumn, in spring and during harvesting was determined also by meteorological parameters as air temperature and precipitation. Oilseed rape field germination was observed from 84% sown on 1st of August in 2007 till 67% sown on 1st of August in 2008. A significant impact (p<0.05) of the sowing rate was noted for plant winterhardiness (in points) for variety 'Californium' in both years: 2008 and 2009. Fungicide application effect on plant survival during winter was observed for treatments with greater plants density. A very little average plant number decrease per m² during summer growth period was noted for all treatments in both years - within 1 to 4% in some cases. The tendency was observed that final plant density at harvest if greater sowing rates had been used, was never high on average for 'Californium' from 75 plants per 1 m² (120 germinable seeds per m²) to 60 plants per 1 m² (100 germinable seeds per m² ) in 2009. Correlations between plant density at harvest time and seed yield were found. [ABSTRACT FROM AUTHOR]

Winter oilseed rape (Brassica napus L.) is an important field crop in Latvia, but its cultivation is subjected to wintering stress. Research on the impact of plant growth regulators to rape wintering in Latvia is still needed. Field trials were carried out at Research and Study farm „Vecauce" in 2012/2013. Three plant growth regulators were used: Caryx (different application times and rates), Toprex 375 SC and Juventus 90 s.c. Results showed that influence of plant growth regulators on seed yield and 1000 seed weight was insignificant. The highest seed yield (5.38 t ha-1; P > 0.05) was obtained using Caryx 1.0 L ha-1 in spring. [ABSTRACT FROM AUTHOR]