engleski

Effect of liming on essential and detrimental trace elements transfer into food chain by grains and vegetables

Acid soils are widespread in the continental part of Croatia with acidity as limiting factor either for the field crops yield or their quality. On the other hand, liming caused a significant changes in soil properties modifying soil acidity, nutrients and trace elements availability. The solubility and therefore plant availability of most of the essential heavy metals and trace elements in soils is expected to be remarkably changed after liming. The consequences of changed solubility differ among elements, but also among various crops and vegetables, especially among different consumable parts of crops (grain) or vegetables (root, leaves, fruits). Considering crop grains and vegetables as a very important sources of minerals in food, liming may result in multiple positive results as increasing Mo content and decreasing content of Cd, Cr, Pb and Ni. Simultaneously, liming can decrease content of essential minerals as Fe, Mn, Zn and Cu. Therefore, the aim of this study was testing liming influence on essential and detrimental trace elements in crop grains and some vegetables. The study is result of two separated experiments. First experiment was conducted in continental Croatia as four-year filed trials on very acid dystric luvisol (pHKCl 4, 02) limed with 0, 10 or 20 t/ha sugar factory waste lime on soil depth 30 cm. In second season, 14 months after liming, maize was grown, in third season winter wheat and in fourth season soybean. Second was pot experiment with very acid soil from orchard (pHKCl 4, 21) limed with 0 and 10 t/ha lime. In 3, 5 L pots with 5 kg of soil, hot pepper and lettuce were grown. In both experiments edible plant parts (grains, fruits or leaves) were collected for analyses of Fe, Mn, Zn, Cu, Mo, Ni, Co, Cr and Cd concentrations after digestion of samples in microwave oven. Liming didn’t cause consistently decreasing of iron (Fe) in grains and vegetables. Fe in wheat grain was decreased 6, 6 % by lower liming dose and 9, 5 % by higher dose, and in soybean by 1, 9 and 4, 8 %. On the other hand, liming didn’t affect Fe concentration in maize grain although maize was harvested 20, wheat 29 and soybean 44 months after liming. The liming experiment with vegetables resulted without effect on Fe in hot pepper but decreased Fe in lettuce leaves by 24 %. Manganese (Mn) concentration was also decreased at least in maize grain (7, 6 %) and the most in lettuce (77, 6 %). Different liming doses decreased Mn in wheat 19, 0 and 23, 1 % and in soybean 11, 3 and 24, 5 %. Hot pepper also accumulated 56, 5 % less Mn after liming than in acid soil. Very similar was influence on Zn concentrations since lower and higher doses decreased Zn in maize only 3, 9 and 5, 2 %, in wheat 4, 1 and 9, 4 % and in soybean 5, 4 and 13, 9 %. Decreasing Zn concentration was not significant in hot pepper (7, 9 %), but was the highest in lettuce (32, 3 %). Copper (Cu) concentrations weren’t significantly affected by liming although concentrations were 6, 3-7, 8 % lower in soybean, 9, 1 % in hot pepper and 17, 4 % in lettuce. Molybdenum (Mo) was the only trace element with increased concentrations as a result of liming. The lowest increasing was 37, 2 % in lettuce and 39, 7 % in hot pepper. Lowest liming dose increased Mo in maize 37, 7 %, and in wheat and soybean 51, 5 %. Highest liming dose increased Mo in maize grain also 51, 5 %, but significantly more in wheat (67, 1 %) and soybean (77, 6 %). Cobalt (Co) was in very low concentrations in all maize and wheat samples and therefore decreasing after liming was measured only in soybean grain (12, 9 %). Co concentrations were also low in vegetables, but still significant decreasing as result of liming was measured in hot pepper (36, 5 %) and lettuce (52, 6 %). Chromium (Cr) concentrations were also very low, especially in maize grain. Nevertheless, liming affected in further decreasing of Cr in wheat (24, 3-32, 3 %), soybean (20, 5-21, 3 %), hot pepper (19, 4 %) and lettuce (18, 2 %). Nickel (Ni) concentrations were significantly decreased in all analyzed samples after liming, starting from maize (19-35 %), soybean (35-42 %), wheat (41-47 %) and ending whit highest decreasing in lettuce (50, 2 %) and hot pepper (65, 4 %). Cadmium (Cd) concentrations were in maize grain below detection limit, in wheat grain was 0, 105 mg kg-1 on very acid soil, but lower liming dose decreased Cd concentration 25, 7 % and highest dose 37, 1 %. Liming resulted in decreasing Cd in soybean by 43-54 %, in hot pepper 35, 8 % and in lettuce 20, 7 %. Finally, liming had lowest influence on maize (Mn, Mo and Ni), stronger impact on wheat (no changes in Cu and Co, small changes in Zn and Fe concentrations), even highest on soybean (no changes only in Cu) and the highest changes were in trace elements concentrations in lettuce. Liming caused the highest relative decreasing of Ni concentrations and lowest decreasing of Zn and Co. No decreasing were significant for Cu. The most consistent relative changes in concentrations caused by liming acid soils were increasing of Mo concentrations.

food chain ; grain ; vegetable ; heavy metals ; Zn ; Cu ; Mo ; Ni ; Cd ; Co ; Cr

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