بررسي اثر مقادير مختلف كود شيميايي اوره در تجمع نيترات در اندام هاي قابل مصرف اسفناج و جعفري

EFFECT OF DIFFERENT AMOUNTS OF UREA ON NITRATE ACCUMULATION IN EDIBLE PARTS OF SPINACH AND PARSLEY

Vegetable crops generally receive excessive amounts of fertilizers, especially nitrogen fertilizers. Recent attention has been focused on the possibility of over fertilization with nitrogen, due to their effects on the human health. Many species are known to accumulate nitrate. The nitrate has no toxic effects on plants, but it will be converted to nitrite, injurious to human consuming the crops. The objective of this project was to investigate the effect of different nitrogen levels on yield and accumulation of NO3-N in the edible parts of spinach and parsley. Five different nitrogen levels of 0, 50, 100, 150 and 200 Kg N ha-1 were used in complete randomized blocks in 1998 for spinach. Nitrogen levels of 0, 80, 160, 240 and 320 Kg N ha-1 were also used in complete randomized blocks for parsley in 1999 in Khalat Pooshan research station in Tabriz University. The results showed that with increasing of nitrogen levels for spinach and parsley, the yield was increased. Also, application of nitrogen fertilizer had significant effects on nitrate accumulation in spinach and parsley. Considering the accumulation of nitrate, there were remarkable differences among leaf blades, petiols and stems in both vegetables. Nitrate concentration in leaf blades was lower than petiols and stems. The average of nitate concentration in different nitrogen levels in leaf blades of spinach was 0.524% D.W. and in parsley was 0.21% D.W. In order to have an acceptable yield and a low concentration of nitrate in these two vegetables, it is recommended to use 50 Kg N ha-1 for spinach and 80 Kg N ha-1 for parsley, in different areas of vegetable crops production in Tabriz.