LO 5.2 - Macro and Micro elements

Macronutrients * Nitrogen (N) * Phosphorus (P) * Potassium (K) * Calcium (Ca) * Magnesium (Mg) * Sulfur (S) * Carbon (C) * Hydrogen (H) * Oxygen (O) Macro and Micro Elements

• Part of chlorophyll molecule • Essential for growth of roots and above-ground parts, gives foliage a strong green colour. • Toxicity of N is rare, but when levels are excessive crops can be a darker green than normal, excessively leafy and slow to mature. • Sources of nitrogen include organic fertilisers and products such as urea and calcium ammonium nitrate. Nitrogen

• Plants deficient in nitrogen smaller, spindly stems, pale or yellowish leaves (chlorosis). Nitrogen

Plant analysis: * 2.2% N on left (deficient). * 4.8% N on right (normal) Normal range 3.5% to 5.5%N. Nitrogen

Plant analysis: * 2% N on lower leaf (deficient) * 5% N on top leaf (normal) Normal range 3.5% to 5.5%N. Nitrogen

• Phosphorus (P) is required in plants for cell metabolism. • Necessary for root development. Seedlings and young plants have a high (P) requirement. Phosphorus (P)

• Plants that are deficient in phosphorus (P) have restricted growth and fruit production. • Some plants have a purplish discolouration on their leaves. Phosphorus (P)

• Deficient leaves: 0.04% P • Normal leaves 0.49% P • Normal range 0.35% to 0.75% Phosphorus (P)

• Phosphorus (P) occurs in soils in organic and inorganic forms. • Organic (P) originates from plant and animal residues. • Inorganic (P) exists as rock phosphate. • Much of the (P) in a soil is in an unavailable form. It is released gradually from the breakdown of soil minerals and from organic matter. • Excess phosphorus can show up as zinc or iron deficiency symptoms – chlorosis, leaf distortion. Phosphorus (P)

• Important for enzyme activity in plants. • Gives some drought, disease and frost tolerance to plants. • Enhances flower colour and taste/texture of many fruits and vegetables. Potasium (K)

Potassium (K) is mobile in plants, so deficiency symptoms are seen in the older leaves first. * (Plants will always try to supply nutrients to their youngest leaves first, so mobile elements such as N, P and K will be moved to the younger leaves.) Potasium (K)

Potassium (K) deficiencies. * Leaf mottling * Pale leaf margins later becoming ‘scorched’ * Tendency to wilt (K balances the effects of N by ‘hardening up’ growth) * Reduced growth Excess potassium can induce nitrogen deficiency symptoms. Potasium (K)

Affected leaves: 0.6% K Normal leaves 4.5% K Normal range 2.5% – 5% K Potasium (K)

‘Scorching’ of leaf margins Potasium (K)

Almost all soil Potassium (K) comes from inorganic sources – for example mica which occurs in igneous and metamorphic rock. The Potassium (K) is released slowly by weathering. * Young volcanic soils are usually high in Potassium (K). * Only small amounts of Potassium (K) are found in organic matter. * Potassium (K) fertilisers include sulfate of potash and potassium chloride. Potasium (K)

• Important part of plant cell walls. • Has a role in cell division. • Regulates transport of other nutrients in the plant. Calcium (Ca)

• Symptoms include pale leaf margins followed by necrosis (death of tissue). • Symptoms tend to show in growing tips as Calcium (Ca) is relatively immobile in plants. • Disorders such as blossom end rot in tomatoes and tip burn in lettuce and brassicas are caused by Calcium (Ca) deficiency. Calcium (Ca)

• Leaves from affected plant contained 0.22% Calcium (Ca). • Normal plant contained 0.92% Calcium (Ca). Calcium (Ca)

• Affected fruit contains less than 0.08% Calcium (Ca). • Normal fruit contains 0.12 to 0.25% Calcium (Ca). Calcium (Ca)

• Reduced growth, as the efficiency of photosynthesis is reduced. • Constituent of chlorophyll, important in protein synthesis. • Magnesium (Mg) is mobile in plants, so deficiency will show in older leaves first. • Interveinal chlorosis (yellowing between the veins, sometimes becoming brown and ‘scorched’). • Found in Epsom salts and Dolomitic limestone. Magnesium (Mg)

• Excess magnesium can interfere with calcium uptake, causing necrotic spots in older leaves and browning of small veins in older leaves. Magnesium (Mg)

• Sulfur is important in the production of proteins. • It is also involved in enzyme activity. Sulfur (S)

• Symptoms include yellow or yellow-green leaves and stunted growth. • Can be confused with nitrogen deficiency symptoms. Sulfur (S)

• Symptoms include yellow or yellow-green leaves and stunted growth. • Can be confused with nitrogen deficiency symptoms. Yellow-green leaf in top is deficient in Sulfur. Sulfur (S) deficiency (Chrysanthemum) Sulfur (S)