NARDI FUNDULEA, ROMANIA ROMANIAN AGRICULTURAL RESEARCH, NO. 35, 2018 www.incda-fundulea.ro Print ISSN 1222‒4227; Online ISSN 2067‒5720 ________________________________________ Received 12 January 2017; accepted 15 January 2018. First Online: February, 2018. DII 2067-5720 RAR 2018-2 PEDOLOGICAL DROUGHT INFLUENCE ON SOME PARAMETERS OF SOYBEAN CROPS FROM CRISURILOR PLAIN Cristian Domuța*, Ana Pereș, Radu Brejea, Ioana Borza, Mariana Bei, Köteles Nandor, Manuel Gîtea, Eugen Jude University of Oradea, Faculty of Environmental Protection, 26 Gen. Magheru street, 410048 Oradea, Romania *Corresponding author. E-mail: cristian_domuta@yahoo.com ABSTRACT The paper is based on the research conducted at the Agricultural Research and Development Station Oradea. Decadal determination of soil moisture, calculus of the water reserve and its dynamic graphs allowed the determination of the number of days with pedological drought, respectively of strong pedological drought. Pedological drought as well as strong pedological drought were present every year during the period 2007-2015 with the only difference that the strong pedological drought in fewer days. The optimum irrigation rate was 2800 m 3 /ha . The irrigation determined the increase of the daily water consumption values and total water consumption. Finally, due to drought, an average yield loss of 65% was recorded, as well as a decrease in protein content up to 24% and in gross protein up to 31%. An inverse correlation between the number of days with pedological drought and water consumption of the soybean yield, as well as with the protein content of the grains and the gross protein content was established. These correlations emphasized the necessity of irrigation in the soybean crop in Crisurilor Plain. Key words: pedological drought, strong pedological drought, water consumption, yield, protein, gross protein, soybean. INTRODUCTION oybean is one of the most important agricultural plants, due to its usage in both human and animal nutrition and industry. In the case of soybeans, its entire amount of biomass can be used, especially the seeds that are rich in protein substances (27.0 to 50.0%), non nitrate extractives (23-30%), fats (18- 22%), vitamins and minerals. Soybean flour is used in bread, as additives in soups, protein concentrates and "vegetable meat" etc. Soybean occupies the first place in the world in the production of vegetal fats; it is used in the preparation of margarine, in obtaining plastic and colours for painting; the seeds and green pods are used in the preparation of food rich in vitamins and minerals. Soybeans represent a valuable concentrated fodder; the green plant can be used as green mass, hay or silage (alone or mixed); the groats and oilcakes remaining after the extraction of oil represent valuable fodder (Bîlteanu, 2003; Borza, 2007; Borza and Stanciu, 2010; Stepănescu and Mate, 1972; Domuța, 2011, 2012; Domuţa and Domuța, 2016; Muntean et al., 2008). Soybean has a special agricultural importance. Because of its symbiosis with bacteria Rhizobium japonicum, it fixes 80-120 kg/ha of atmospheric nitrogen in the soil out of the huge amount of 200,000 tons nitrogen that can be normally found in the atmosphere over a hectare of land (Domuţa et al., 2008). Soybean is a crop with relatively high requirements to humidity. In drought conditions the yield decreases with 31-61% (Enciu, quoted by Domuta, 2009). Drought recorded during the flowering period determines the decrease of the yield with 14-52% and the drought during the period of grain filling determines a higher yield loss. Thus, the soybean yield affected by drought represents 13-59% of the irrigated soybean yield (Berbecel and Valuță, quoted by Domuta et al., 2012; Picu, 2003). The irrigation of soybean in Crisurilor Plain was studied starting with 1976 by M. Stepănescu. He made research at Girişu Cris (1967-1975) and Oradea (1976-1980) in the field on water balance in the soil. Research of the water balance in the soil S