Irrigation and Nitrogen Fertilization Influences on Properties of Soybean (glycine Max (l.) Merr.) Varieties

Soybean is an important industrial crop in Croatia and in the last ten years (2000-2009) mean soybean harvested area was 45888 ha (from 35789 to 62810 ha) with average seed yield 2.0 t ha-1 (Central Croatian Bureau of Statistic, 2010). Seed yields of soybean varied in close connection with amount and distribution of precipitation during the vegetation period (Vučić and Bošnjak, 1980; Bošnjak, 2008; Kovačević et al., 2010; Josipović et al., 2010), intensity and longings of dry period in different growing stage (Rao and Reddy, 1990; Dragović, 1994; Brevedan and Egli, 2003; Bošnjak, 2008), properties of cultivars (Sudarić et al., 1996; Sudarić et al., 2004; Sudarić et al., 2009) soil properties and successful performing of other agro technical measures (Sudarić et al., 2009, Fehr, 1983 and Specht et al., 1999 according to Sudaric et al., 2004). Some general aspects of irrigation and nitrogen (N) fertilization effects were shown by Mađar and Vratarić (1980), Vučić and Bošnjak (1980), Bošnjak et al. (2008), Josipović et al. (2010). Bošnjak (2008) and Josipović et al. (2010) confirmed that the highest soybean seed yield was when the soil water content was maintained from 60% field water capacity (RWC) to 100% RWC. The mentioned authors also confirmed, that maintenance soil water content from 80% RWC to 100% RWC resulted in seed yield lower than on the irrigation control treatment. Vučić (1976) confirmed that irrigation, in most cases of growing soybean, increased seed yield by 30% while Mađar and Vratarić (1980) achieved higher seed yield from 23% to 49%. ISSN 1330-7142 UDK = 633.34:631.67+631.811.1