Isoflavone and protein contents in soybean under irrigation and nitrogen fertilisation management

There is awareness that proper agronomic practices are the main key to production for several field crops. In soybean, both grain yield and accumulation of secondary metabolites (e.g., isoflavones) depend on several factors, including environment, variety, and agronomic practices (Lozovaya et al., 2005). Yield and its main components (e.g., carbohydrates, proteins, fatty acids) are not as sensitive to changes in agronomic practices as secondary metabolic compounds (Berger et al., 2002). Soybean isoflavones are polyphenol compounds derived from polypropanoid metabolism, which accumulate in various forms in the seeds. Isoflavones have recently attracted the attention of the pharmaceutical industry as a good source of phytoestrogens. Soybean proteins and isoflavones have positive effects on human health if they are correctly integrated in human diet. Consumption of soy-foods is associated with many health benefits, such as lowered risk of breast, prostate and colon cancer (Lacombe et al., 2000). In poor countries, soybean protein may become a substitute for animal milk in the form of soymilk. This study examines the effects of cultivar choice, supplementary irrigation and nitrogen on isoflavone and protein production in soybean, and their relation with nodule activity (N fixation, ureide production).