Influence of Water Deficit on the Chemical Composition of Soybean Grains

Abstract

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.