Industrial discharge Air Human uptake Animal accumulation Fertilizers Pesticides Surface water Plant and animal residue, microbial pool Plant uptake Soil.

Industrial discharge Air Human uptake Animal accumulation Fertilizers Pesticides Surface water Plant and animal residue, microbial pool Plant uptake Soil Organic Matter Minerals: Spharelite, Zincite, etc. SOIL CLAYS: Muscovite Illite Chlorite Montmorillonite Kaolinite Zn 2+ and chelates Available at pH < 7.7 Hydrolysis Species Phosphate and Nitrate Complexes Chloride Complexes Highly soluble compounds: Hydroxides Carbonates Silicates Chlorides Sulfates Phosphates Main Cycle Rainfall Adsorption + nH 2 O Precipitation + nCl Complexation + H 2 PO 4 or nNO 3 Complexation Choose Your Own Adventure With Zinc Where you can go Legend Where you have been Where you are Immediate interactions Click on an object and follow the arrows to choose your own adventure within the Zinc cycle More Info

Industrial discharge Air Human uptake Animal accumulation Fertilizers Pesticides Surface water Plant and animal residue, microbial pool Plant uptake Soil Organic Matter Minerals: Spharelite, Zincite, etc. SOIL CLAYS: Muscovite Illite Chlorite Montmorillonite Kaolinite Hydrolysis Species Phosphate and Nitrate Complexes Chloride Complexes Highly soluble compounds: Hydroxides Carbonates Silicates Chlorides Sulfates Phosphates Rainfall Adsorption + nH 2 O Precipitation + nCl Complexation + H 2 PO 4 or nNO 3 Complexation Choose Your Own Adventure With Zinc Zn 2+ and chelates Available at pH < 7.7 Where you can go Legend Where you have been Where you are Immediate interactions Click on an object and follow the arrows to choose your own adventure within the Zinc cycle Main CycleMore Info

More Info on Zinc Form taken up by plant Mobility in soil Mobility in plants Deficiency found in Toxicity symptoms Role of Zn in the plant Role of Zn in microbial growth Concentration in plants Concentration in soils Origin in soils Effect of pH on availability Interaction of Zn with other nutrients Fertilizer sources Soil test References Back to Main Cycle Back to More Info

Form taken up by plant: Zn 2+ at pH 7.7 (less available to plants). Mobility in soil: No (Low solubility): Soluble by chelation by mobile ligands. Highly soluble at pH < 6. Mobility in Plants: Low: Mobility in plants does not coincide with water flow. Zn is absorbed by plants as Zn 2+ and transported as citrate, malate and malonate complexes. More Info on Zinc Back to Main Cycle Back to More Info

Deficiency found in: Acidic, sandy soils with high leaching, calcareous soils pH>8.0, exposed subsoil horizons (erosion), Deficiency symptoms are purple margins similar to phosphorus deficiency, but also inward toward the center of leaves (purple blotching), and brown spots on rice leaves. Deficiency is rarely observed in wheat. Zn deficiency can be corrected by application of 2.5-25 kg/ha of ZnSO 4 (depending on soil pH and texture) or 0.3-6 kg/ha as chelates in broadcast or band application. Foliar application of 0.5-2.0% ZnSO 4 *7H 2 O effective for fruit trees for the growing season; 2% solution is used for seed soaking. Soil application corrects Zn deficiency for 2-5 years. More Info on Zinc Back to Main Cycle Back to More Info

Toxicity symptoms: Most plant species have high tolerance to excessive amounts of Zn. However, on acid and heavily sludged soils Zn toxicity can take place. Zn toxicity symptoms as follow: Inhibited root elongation, photosynthesis in leaves, depresses RuBP carboxylase activity, chlorosis in young leaves due to induced deficiency of Fe 2+ and/or Mg 2+. Zn 2+ has ion radius similar to Fe 2+ and Mg 2+, which creates unequal competition for these elements when zinc supply is high. The critical toxicity level in leaves is 100-300 mg per kg of dry weight. More Info on Zinc Back to Main Cycle Back to More Info

Role of Zn in the plant: 1. Component of ribosomes. 2. Carbohydrate metabolism a) a cofactor of carbonic anhydrase, which converts CO 2 into HCO 3 - b) activity of photosynthetic enzymes: ribulose 1,5 bisphosphate carboxylase (RuPPC) c) Chlorophyll content decreases and abnormal chloroplast structure occurs when Zn is deficient d) Sucrose and starch formation by activating aldolase and starch synthetase 3. Protein metabolism: Stabilizes DNA and RNA structures 4. Membrane integrity: Stabilizes biomembranes and neutralizes free oxigen radicals, as a part of superoxide dismutase 5. Auxin metabolism: Controls tryptophane synthetase, which produces tryptophane, a source for IAA 6. Reproduction: Flowering and seed production are depressed by Zn deficiency. More Info on Zinc Back to Main Cycle Back to More Info

Role of Zn in microbial growth: Indispensability of Zn in metabolism of living organisms, microflora also is highly dependent on concentrations of zinc present. Some heterotrophs can tolerate high concentration of Zn and behave as bioaccumulators of Zn, among them Zoogloea-producing bacteria, Ephiphytic bacteria, Nonsporing bacteria. Different genera of Green Algae respond differently to Zn contamination. Microspora, Ulothrix, Hormidium, and Stigeoclonium are resistant to high Zn concentrations, whereas genera such as Oedogonium and Cladophora are rather sensitive to the presence of Zn. More Info on Zinc Back to Main Cycle Back to More Info

Concentration in plants: Depending on genotype, Zn concentration varies in the range 25-150 ppm (0.0025-0.015% of dry weight) of Zn sufficient plant. Concentration in soils: 10-300 ppm (0.001-0.03%). Concentration of total Zn increases with depth, whereas extractable Zn content decreases. Concentration of Zn in the upper horizon also depends on organic matter content, which can hold up to 13% Zn. In soils, 30-60% Zn can be found in iron oxides, 20-45% in the lattice of clay minerals, and 1-7% on clay exchange complex. Highest Zn concentration is in solonchaks – saline soils in Asia, lowest in light textured soils with low organic matter. More Info on Zinc Back to Main Cycle Back to More Info

Origin in soils: Zinc composition of soils defined by parent material. Magmatic rocks have 40 and 100 mg/kg Zn in granites and basalt, respectively. Sedimentary rock composition varies in the range 10 to 30 mg/kg in sandstones and dolomites, and 80-120 mg/kg in clays, Effect of pH on availability: pH is the most important parameter of Zn solubility. General equation for soil Zn is pZn = 2pH – 5.8 The form of Zn predominant at · pH<7.7 – Zn 2+ · pH>7.7 – ZnOH + · pH<7.7 – Zn(OH) 2 More Info on Zinc Back to Main Cycle Back to More Info

Interaction of Zn with other nutrients: Increase in available P content can considerably decrease availability of Zn in the soil due to the high antagonism between these two elements. However, some authors suggest that symptoms considered as a Zn deficiency are actually P toxicity. Presence of other nutrients such as iron, copper, manganese and calcium may also inhibit Zn uptake by plants, probably due to the competition for the carrier sites on roots. Application of high rates of NPK fertilizers can aggravate Zn deficiency. More Info on Zinc Back to Main Cycle Back to More Info

Fertilizer sources: Zinc sulfate with 25-36%Zn, Zinc oxide – 50-80% Zn, Zinc Chloride - 48% Zn, Zinc Chelate – 9-14.5% Zn, and manure are used in agriculture. Soil Test: For available Zn determination four extractants are generally used: 0.1M HCL, EDTA-(NH 4 ) 2 CO 3, Dithizone - NH 4 OAC, and DTPA-TEA. Soil content of Zn of 2ppm (0.0002%) and higher are sufficient for most of the crops, <2 ppm is deficient for pecans, <0.8 ppm is deficient for corn. When Zn concentration is less than 0.3 ppm, deficiency symptoms are observed in less sensitive crops such as cotton, wheat, soybean, etc. More Info on Zinc Back to Main Cycle Back to More Info

References: Allowey, B.J. (ed.). 1990. Heavy Metals in Soils. John Wiley and Sons. New York. Johnson, G.V., W. R. Raun, H.Zang, and J.A. Hattey. 1997 Oklahoma Soil Fertility Handbook. 4 th ed. Department of Agronomy Oklahoma State University. Kabata-Pendias, A., H. Pendias. 1991. Trace elements in soils and plants. 2 nd ed. CRC Press Boca Raton Ann Arbor London. Nriagu, J.O. (ed.). 1980. Zinc in the Environment. John Wiley and Sons. New York. Prasad, R., and J.F. Power. 1997. Soil Fertility Management for Sustainable Agriculture. CRC Press LLC. New York. Raun, W.R., G.V. Johnson, R.L. Westerman. 1997. Soil - Plant Nutrient Cycling and Environmental Quality. Oklahoma State University. Robson, A.D. (ed.). 1993. Zinc in Soils and Plants. Kluwer Academic Publishers. Australia. Marschner, H. 1995. Mineral Nutrition of Higher Plants. 2 nd ed. Academic Press. London. Tisdale, S.L., W.L. Nelson, J. D. Beaton, and J.L. Havlin. 1993. Soil Fertility and Fertilizers. 5 th ed. MacMillian. USA. Authors: Francisco Gavi, Chad Dow, John Ringer, Erna Lukina, and Jon-Karl Fuhrman More Info on Zinc Back to Main Cycle Back to More Info

Industrial discharge Air Human uptake Animal accumulation Fertilizers Pesticides Surface water Plant and animal residue, microbial pool Plant uptake Soil.

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Industrial discharge Air Human uptake Animal accumulation Fertilizers Pesticides Surface water Plant and animal residue, microbial pool Plant uptake Soil.

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