NITROGEN FERTILIZERS AND THE AMOUNT OF VITAMINS IN PLANTS - A REVIEW

Effect of mineral fertilizers on the vitamin content of plants has rec eived very little attention by scientists in English-speaking countrie s, especially in recent years. A review of the literature, however, ha s revealed a rich source of information mostly published in non-Englis h journals. Based on these reports, nitrogen fertilizers, especially a t high rates, seem to decrease the concentration of vitamin C in many different fruits and vegetables, among them potatoes, tomatoes and cit rus fruits, the major sources of this vitamin in human nutrition in ma ny societies. Nitrogen fertilizers are also shown to increase the conc entrations of carotenes and vitamin B-1 in plants. Since excess use of nitrogen fertilizers increases the concentration of NO3 in plant food s and simultaneously decreases that of ascorbic acid, a known inhibito r for the formation of carcinogenic N-nitroso compounds from nitrite, it appears that the use of these fertilizers may have a double negativ e effect on the quality of food plants. Vitamin C and several caroteno ids have antioxidant properties and reportedly reduce the risk of card iovascular diseases and some forms of cancer. Whether long-term consum ption of food plants grown with excess use of nitrogen fertilizers wou ld have an overall positive or negative effect on the total intake of antioxidative vitamins by consumers warrants investigation.