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Humic acids have many benefits for plant growth and development, and these effects may be maximized if these materials are combined with micronutrient applications. In the present study, pot experiments were conducted to evaluate the effects of zinc (Zn) humate and ZnSO 4 on growth of wheat and soybean in a severely Zn-deficient calcareous soil (DTPA-Zn: 0.10 mg kg 21 soil). Plants were grown for 24 (wheat) and 28 days (soybean) with 0 or 5 mg kg 21 of Zn as either ZnSO 4 or Zn humate. Zinc humate used in the experiments was obtained from Humintech GmbH, Germany, and contained 5% of Zn. When Zn was not supplied, plants rapidly developed visible symptoms of Zn deficiency (e.g., chlorosis and brown patches on young leaves in soybean and necrotic patches on middle-aged leaves in wheat). Adding Zn humate eliminated Zn-deficiency symptoms and enhanced dry matter production by 50% in soybean and 120% in wheat. Zinchumate and ZnSO 4 were similarly effective in increasing dry matter production in wheat; but Zn humate increased soybean dry matter more than ZnSO 4 . When Zn was not supplied, Zn concentrations were 6 mg kg 21 for wheat and 8 mg kg 21 for 2769 Downloaded by [Akdeniz Universitesi] at 12:45 21 December 2014 soybean. Application of Zn humate and ZnSO 4 increased shoot Zn concentration of plants to 36 and 34 mg kg 21 in wheat and to 13 and 18 mg kg 21 in soybean, respectively.The results indicate that soybean and wheat plants can efficiently utilize Zn chelated to humic acid in calcareous soils, and this utilization is comparable to the utilization of Zn from ZnSO 4 . Under Zn-deficient soil conditions, plant growth and yield can be maximized by the combined positive effects of Zn and humic acids.

Cadmium (Cd) accumulation in durum wheat grain is a growing concern. Among the factors affecting Cd accumulation in plants, soil chloride (Cl) concentration plays a critical role. The effect of leaf NaCl application on grain Cd was studied in greenhouse-grown durum wheat (Triticum turgidum L. durum, cv. Balcali-2000) by immersing (10 s) intact flag leaves into Cd and/or NaCl-containing solutions for 14 times during heading and dough stages. Immersing flag leaves in solutions containing increasing amount of Cd resulted in substantial increases in grain Cd concentration. Adding NaCl alone or in combination with the Cd-containing immersion solution promoted accumulation of Cd in the grains, by up to 41%. In contrast, Zn concentrations of grains were not affected or even decreased by the NaCl treatments. This is likely due to the effect of Cl complexing Cd and reducing positive charge on the metal ion, an effect that is much smaller for Zn. Charge reduction or removal (CdCl 2 0 species) would increase the diffusivity/lipophilicity of Cd and enhance its capability to penetrate the leaf epidermis and across membranes. Of even more significance to human health was the ability of Cl alone to penetrate leaf tissue and mobilize and enhance shoot Cd transfer to grains, yet reducing or not affecting Zn transfer.