Changes of Winter Oilseed Rape Plant Survival During Vegetation

Winter oilseed rape (Brassica napus L.) significance among field crops is unchangeable in Latvia in the last decade. Plant density of winter oilseed rape during growth period is influenced by plant development in autumn and plant wintering. The aim of four year (2008 – 2011) research in the LLU Research and Study farm “Vecauce” was to investigate the influence of agronomical factors (sowing date, sowing rate, fungicide (metkonazole)) application and meteorological factors on two type (line, hybrid) winter oilseed rape varieties plant density changes from sowing till harvesting. Plant density in autumn, spring and during harvesting was influenced also by meteorological parameters such as air temperature and precipitation. On four year average, field germination was observed from 66% to 95%. Sowing date significantly (p<0.05) impacted plant survival during winters in all trial years for both varieties – ‘Californium’ and ‘Excalibur’, except for ‘Excalibur’ in the year 2008. Plant survival during winter for ‘Excalibur’ (hybrid) was higher compared to ‘Californium’ (line). Higher plant losses during winter were noted on the latest sowing date for both varieties. Winter oilseed rape plant survival was not significantly (p>0.05) influenced by fungicide as growth regulator application in autumn in any trial year. Influence of sowing date and sowing rate on the total plant density at harvest time was significant in all trial years (p<0.05) for both varieties. At higher sowing rate the plant loss during growing period was higher than at lower rates.

SPECIFIC EMISSIONS FROM BIOMASS COMBUSTION

This paper deals with determining the specific emissions from the combustion of two kinds of biomass fuels in a small-scale boiler. The tested fuels were pellets made of wood and pellets made of rape plant straw. In order to evaluate the specific emissions, several combustion experiments were carried out using a commercial 25 kW pellet-fired boiler. The specific emissions of CO, SO₂ and NO_x were evaluated in relation to a unit of burned fuel, a unit of calorific value and a unit of produced heat. The specific emissions were compared with some data acquired from the reference literature, with relatively different results. The differences depend mainly on the procedure used for determining the values, and references provide no information about this. Although some of our experimental results may fit with one of the reference sources, they do not fit with the other. The reliability of the references is therefore disputable.

Initial Evaluation of the Effectiveness of Selected Active Substances in Reducing Damage To Rape Plants Caused By Arion Lusitanicus (Gastropoda, Pulmonata, Arionidae)

Initial Evaluation of the Effectiveness of Selected Active Substances in Reducing Damage To Rape Plants Caused By Arion Lusitanicus (Gastropoda, Pulmonata, Arionidae) Spray forms of various chemical compounds including compounds of plant origin, molluscicides, and insecticides were tested in order to investigate their possibilities for reducing damage to young rape plants caused by the slug Arion lusitanicus Mabille, 1868. Among them, abamectin (0.2%), methiocarb (0.5%) and metaldehyde (1.0%) reduced damage to the plants, although metaldehyde remained active for only nine days. These three chemical compounds were not phytotoxic to rape plants, and none of them proved lethal to the slugs at the concentration used. The reduction in rape plant damage was obtained as a result of their deterrent and/or antifeedant action. The results indicate that abamectin has high potential usefulness in protecting winter rape seedlings from slugs.