A field experiment has been conducted in the region of Dobrudja with the aim to investigate the essential oil yield and its chemical composition by four lavender varieties: Hemus, Sevtopolis, Yubileyna and Druzhba. The experiment has been arranged according to the Randomized Complete- Block Design in four replications and a plot size of 10 m2. The essential oil yields varied from 90 l ha-1 by the variety Hemus to 131 l ha-1 by the variety Sevtopolis. The major constituents of the essential oil were linalyl acetate (25.5-39.7%) and linalool (27.6- 38.9%). The content of linalyl acetate was the highest by the variety Hemus, as only by this variety the ratio between linalyl acetate and linalool is 1:0.7, which defined the essential oil as high qualitative.
The efficiency of crop irrigation depends largely on the extent of the root system and the corresponding depth at which the soil is moistened by irrigation. The incorrect determination of irrigation rates can cause water stress or unnecessary irrigation costs, and in both cases the efficiency of irrigation decreases. The aim of this work is to study the root system of soybean plants irrigated with full and reduced irrigation rates. The research work was been carried out on alluvial meadow soil from Bulgaria. The variety “Biser” is used. Treatments of the experiment: 1) without irrigation; 2) full irrigation (100%m), 3) irrigation with 70% of the full irrigation application rate (70%m), 4) 50%m, 5) 30%m. Water applications in treatment 2 were realized at 80% of FC (field capacity) pre-irrigation soil moisture in the 0-60 cm soil layer. Irrigation water was applied in short closed furrows. The weight of the roots and their distribution in soil layers were established. For this purpose, soil monoliths with dimensions of 10x35x10 cm at a depth of up to 100 cm have been cut. The irrigation regime had a significant impact on the soybean root weight. The small irrigation rates can increase their dry weight by almost a quarter. The higher irrigation rates can increase the root weight between 64 and 73%. The main part of the soybean roots (37-44%), regardless of the irrigation regime, is located in the surface soil layer 0-20 cm. Most of it is in the 10-20 cm soil layer. In the critical soil layer (20-40 cm), 23% of the roots of non-irrigated plants and 27% of the roots of those irrigated with low irrigation rates (30%) are formed. When applying irrigation rates in the range of 50-100%, the relative share is the same (30-31%). If irrigation rate is calculated to moisten the layer 0-40 cm, it can provide water to 67-70% of the entire root system. If it is calculated for 0-60 cm, it covers 86-89% of the root system. The conclusion is that the criterion for irrigation should be provides the optimal soil moisture in the layer 0-40 cm, and irrigation rates should be moisten the soil layer up to 0-60 cm.
With relation to the present issue about the influence of the periodic water deficit on the content and yield of the main chemical components, summarized annual data have been used including years of different characteristics, with droughts in different vegetation phenophases of soybean: very dry, averagely dry and average. The experiment was conducted at the Agricultural University of Plovdiv. The experiment was set in 4 repetitions with a size of experimental plots - 30 m 2 , and the crop plots - 10 m 2 . Criteria for watering performance was pre-watering moisture of soil at option 5-80% under-soil moisture for the layer 0-60 cm. The irrigation norm for all options was 50 mm. The irrigation norm for option 5 was 150 mm, and for options 2, 3 and 4-100 mm. Irrigation was performed gravitative along short closed furrows. After the completion of all experimental options, there were established the content and yield of the main chemical components in soybean grains - raw fat content, raw protein, raw fibres, raw ash and non-nitrogen extracted substances. Watering cancellations in the period of seed filling decrease the raw protein content. Watering cancellation in the bean formation period has a negative influence on protein content in soybean or does not influence it at all. Watering cancellation during the reproductive period decreases raw protein yield, which leads to a decrease in grain yield. Regarding raw fats, the most favourable is the water cancellation in the period of seed filling which favours growth in their content. Watering cancellation in the period of seed filling leads to a more significant decrease in lysine content. Despite the watering cancellation in a particular phase, the application of the other two waterings increases carbohydrate content in soybean grains compared to that obtained in non-watering conditions.
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