Tomato investigations were carried out under greenhouse and field conditions. The aim was to determine the extent to which greenhouse conditions influence the chemical composition of tomato fruits. Plants grown under field conditions were used as the control. Tomato trials were performed during different periods. Greenhouse trials were carried out in the winter and the spring period (January-June), and field trials in the spring and the summer period (May-September). Zinc (Zn), iron (Fe) and copper (Cu) content was established in ripe tomato fruits.

The methods for estimating Fe, Mn and Zn solubility in smonitzas over Serbia (ten localities) used as fields and meadows, were studied in this paper. The total contents of these elements were found to be nearly equal to their mean values in the world soils. Regarding their availability, investigated smonitzas were found to be well supplied with manganese and, for the majority of samples, with iron.