干旱区生态环境知识资源中心

The accumulation of Pb and Cd in the different parts of Triticum aestivum cultivar Vlada corns was investigated. The field stationary trials were carried out at the experimental base of the University of Agriculture in Nitra located in warm, moderately arid region, with loamy brown soil characterised by weak acid soil reaction, rich in accessible nutrients. Three farming systems were applied: Conventional (1) with three variants of nourishment. Conventionally-rational (2) with mineral fertilizers used according to the yield planned and farmyard manure in the autumn prior to root crops. Alternative- -organic (3) only manure applied taking into account return rate of the organic matter and mineral nutrients to soil, excluding herbicides application. In the two just mentioned systems two soil management systems were followed: conventional (k - ploughing depth of 0.24 m) and minimal (m - ploughing depth 0.15 m). Wheat was milled our in the Brabender Quadrumat Senior mill and the values of Pb and Cd were obtained using the anodic-dissolutive-voltmetry method on mercury drop microelectrode with reference to silver-chloride electrode in the four milling fractions (I, II, III, IV). Method of Pb2+ and Cd2+ ions addition was used for evaluations. Reference trials were carried out analogously. Three years investigations (1991 to 1993) results show significant differences in Cd and Pb contents as in the different corn parts as among three farming systems. The highest (highly statistically significant) Cd content was observed for system 1 (Fig. 3). In this system particularly, Cd values even above limit were found out in milling fraction IV. Having evaluated the so-called consumable milling products (fraction I, II, III), we seldom found values above limit (fixed on maximal value of 0.05 mg.kg(-1)) for the fraction III (Fig. 5). No limit overstepping values were obtained for any year and any fraction (Fig. 6). In the case of Pb, the highest (statistically significant) content was obtained for system 3 (Fig. 4). Neither the limiting Pb content values for consumable products (fractions I, II, III - Pb max. 0.5 mg.kg(-1)), nor for bran (fraction IV - Pb max. 1 mg.kg(-1)) were overstepped during the period of the study. Both metals, as Cd as Pb, were prevailingly cumulated in outer - covering parts (fraction IV - bran) and in the more milled out fraction III with only one exception for Pb value for system 1, as can be seen in Fig. 7. The results just reported have great practical importance from the viewpoint of choosing of appropriate milling technique for above limit by heavy metals contaminated cereals processing for consumption. In our conditions, we observed enhanced Cd concentration in the corn envelopes for system 1 in the first year of trials, which caused in expulsion of this material from further reprocessing on whole-corn nourishment products.