Accumulation and distribution of selenium in some vegetable crops grown in selenate-Se treated clay loam soil

Abstract

A greenhouse experiment was conducted to study the accumulation of selenium by some vegetable crops commonly grown in the Indian Punjab. Eleven vegetable crops were raised in an alkaline clay loam soil treated with different levels of selenate-Se, i.e., 0, 1.25, 2.5 and 5.0 mg·kg−1 soil. Dry matter yield of both edible and inedible portions of different vegetable crops decreased with increasing Se level in soil except potato (Solanum tuberosum), radish (Raphanus sativus) and cauliflower (Brassica oleracea var. botrytis) which recorded 10%–21% increase in inedible dry matter at 1.25 mg·kg−1 Se soil. Application of 5 mg·kg−1 selenate-Se soil resulted in complete mortality in the case of radish, turnip (Brassica rapa) and brinjal (Solanum melongena). Some vegetable crops including tomato (Lycopersicum esculentum), cauliflower and pea (Pisum sativum), though, survived the toxic effect at the highest concentration of Se yet did not bear any fruit. Potato and spinach (Spinacea oleracea) proved to be highly tolerant crops. Selenium concentration in the edible as well as inedible portions of all the vegetables increased with an increase in the level of applied Se. Selenium accumulation in the edible portion of vegetable crops in the no-Se control ranged from 2.2 to 4.9 mg·kg−1 Se dry weight. At 1.25 mg·kg−1 Se soil, the edible portion of radish accumulated the greatest concentration of Se (38 mg·kg−1 Se dry weight) with that of onion (Allium cepa) bulb the lowest (9 mg·kg−1 Se dry weight). Inedible portions of vegetables accumulated Se 2–5 times more than that absorbed by edible portions. Total Se uptake by edible portions of different vegetables was the greatest at 1.25 mg·kg−1 Se soil, ranging from 7 to 485 μg·pot−1. The results suggest that vegetable crops vary in their sensitivity to the presence of selenate-Se in soil. Vegetative portions were several times richer in Se than other parts of vegetable crops.