NITROGEN–PHOSPHORUS–POTASSIUM EFFECTS ON FORMS OF SULFUR IN LEAVES AND FRUITS OF CUCUMBER |
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| Abstract: | ABSTRACT The impact that nitrogen (N), phosphorus (P), and potassium (K) application rates on the sulfur (S) fractions in leaves and fruits of greenhouse-grown cucumbers plants (Cucumis sativus L. cv. Brunex) are presented. The treatments were as follows: N (N1=5 g NO3NH4/m2, N2=10 g NO3NH4/m2, N3=20 g NO3NH4/m2, N4=40 g NO3NH4/m2), two levels of P (P1=8 g H3PO4/m2 and P2=16 g H3PO4/m2), and two levels of K (K1=20 g K2SO4/m2 and K2=40 g K2SO4/m2). The foliar and fruit contents were determined for total S, organic S and sulfate. The influence of the N treatments on the total S (St: organic S +sulfate) concentration, proved significant, showing a progressive increase in the leaf and fruit concentrations. In the leaves, the P slightly diminished the St concentration but values in the fruits did not appreciably differ from control. The K dosage did not cause the St concentration to differ from that of P, although in the fruit a slightly lower St concentration appeared in the K2 treatment. The response of the organic-S concentration in the leaves resembled that of St, and thus organic S should not be used as a diagnostic method for S status. In the relationship SO4 2-/St, the SO4 2- concentration proved more influential than did the St form, providing a more accurate representation of the potential status of this nutrient in the plant. |
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