EFFECTS OF NITROGEN FORM OR SOLUTION PH ON CADMIUM CONTENT AND QUALITY OF SPINACH

Two experiments were conducted with spinach grown in NFT. In the first one the effect of nitrogen form (N-NO₃, N-NH₄ and N-NH₂) and in the second one the effect of solution pH (5.0, 6.0, 7.0) on cadmium, soluble sugars, total phenols and oxalate contents in the leaves were studied. Both, nitrogen form and solution pH had a significant effect on the studied parameters. The highest level of cadmium was shown in plants fertilized with N-NH₄ and the lowest when N-NO₃ was used. In addition, cadmium content significantly increased when solution pH was decreased. Plants fertilized with reduced forms of nitrogen contained more soluble sugars and phenols than those fertilized with N-NO3. An increase in solution pH from 6.0 to 7.0 reduced the contents of sugars and phenols in spinach leaves. The content of oxalates depended only on the nitrogen form.