Plant Nutrient Deficiencies - What To Look For And How To Correct Them
Working out if a plant has a nutrient deficiency is one of the first steps in returning a struggling plant back to optimal health. Different deficiencies can be hard to tell apart and there may be more than one present at any time. The following is a general guide that should hopefully help you to identify the collect nutrient deficiency affecting your plants. Additionally it should help to provide ideas on how to remove the causes of the deficiency and adjust your fertilizing schedule to include the appropriate corrective trace element. When adjusting nutrient levels remember that it's always easier to add a small amount several times over than it is to correct a nutrient toxicity (overdose) issue. Always monitor the response to the first application and add more only if required.
Nitrogen (N) Deficiency
Symptoms: Uniform pale green to yellow leaves. Occurs in older leaves first.
Causes: Removal of fallen plant material, not allowing nutrients to return to the soil. Loss via leeching. Decomposition of organic materials with a high Carbon to Nitrogen ratio 'dry compost'. Low levels of humus in soil. Conversion of plant usable forms of nitrogen to nitrogen gas under waterlogged conditions.
Correction: Apply a nitrogen based fertiliser. Use nitrogen-fixing legumes as companion plants.
Phosphorous (P) Deficiency
Symptoms: Dull, lacklustre leaves with a bluish green or purple tinge across the entire leaf surface. Poor growth and lack of vigour. Occurs in the older leaves of the plant first.
Causes: Naturally low levels of phosphorus in soil. Phosphorus may be present but unavailable for the plant uptake as it is bound to clay particles in the soil. Leaching due to excessive watering or rainfall.
Correction: Apply a fertilizer rich in phosphorus.
Potassium (K) Deficiency
Symptoms: Brown scorching common around the edges of leaves. Sometimes there may also be yellowing between leaf veins. Leaf tips may turn inwards giving the leaf a cupped appearance. Occurs in older leaves of the plant first.
Causes: Repeated removal of plant clippings, not allowing nutreints to break down and return to the soil. Leeching, particularly in sandy soils.
Correction: Apply a fertiliser rich in potassium or apply potash.
Magnesium (Mg) Deficiency
Symptoms: Patchy yellowing often with a triangular slither of green running along the central leaf vein. Severe magnesium deficiency causes grey or light brown scorching in some species. Occurs in older leaves of the plant first.
Causes: Too much potassium in the soil will inhibit magnesium uptake. Low soil pH levels will also inhibit uptake. Wet, dry or cold soil conditions.
Correction: Apply dolomite, dolomitic limestone or magnesium sulphate 'Epsom salts'.
Iron (Fe) Deficiency
Symptoms: Near total uniform loss of green colouration between the leaf veins giving the veins of the leaf a green skeletal appearance. Occurs in younger leaves first.
Causes: High bicarbonate levels in irrigation water. Alkaline soils with no additional applications of soluble iron. Excessive applications of phosphorus, copper and zinc will inhibit uptake of iron. Inactivation of plant-usable iron compounds by bark mulches. Wet soils. Low soil temperatures.
Correction: Apply ferrous sulphate.
Zinc (Zn) Deficiency
Symptoms: Reduced leaf size and/or stem length. Leaves will have distinct yellow interveinal patterns. Young leaves will appear distorted. Occurs in younger leaves of the plant first.
Causes: Low natural concentrations of zinc, especially in alkaline soils and some sandy soils. Excessive applications of phosphorus or nitrogen rich fertilisers will inhibit uptake of zinc.
Correction: Apply zinc sulphate.
Copper (Cu) Deficiency
Symptoms: Curled or cupped leaf tips, with narrowing, distortion and/or scorching of the leaf. Defoliation from tip. Interveinal or irregular yellowing. Occurs in the younger leaves of the plant first.
Causes: Low natural levels of copper, especially in sandy soils. Soils natural rich in or modified to be high in iron, manganese, zinc or phosphorus will inhibit copper uptake by plants..
Correction: Apply copper sulphate.
Manganese (Mn) Deficiency
Symptoms: Leaves will show a mottled, diffuse, pale green to yellow interveinal pattern. No reduction of leaf size. Can occur in either new and old leaves first.
Causes: Alkaline soils interfere with the uptake of Manganese by plants. Use of sewage sludge, sawdust or peat for organic material. Excessive applications of iron, copper or zinc. Cool weather.
Correction: Apply manganese sulphate.
Calcium (Ca) Deficiency
Symptoms: Death of growing points or the margins of young leaves. Breakdown of fruit tips leading to rot. Seen first in young leaves and stem tips first and also fruit.
Causes: Very low pH. Excessive applications of ammonium and/or potassium fertilisers combined with high applications of Potassium or Magnesium without added Calcium. High humidity. High pH when accompanied by high sodicity.
Correction: Apply gypsum.
Boron (B) Deficiency
Symptoms: Internal cracking or breakdown of stems and/or roots. Death of growing tips and buds. Surface cracking, giving a corky appearance to the petioles and midribs of leaves. Seen first in young leaves and stem, also affects fruit.
Causes: Low pH soils that have suffered leaching, particularly coarse sands. Dry conditions. Excessive applications of calcium.
Correction: Apply sodium borate 'Borax'.