Coppice Road Allotments Association

www.poyntonallotmentgardeners.org.uk

(affiliated to the National Society of Allotment and Leisure Gardeners Ltd)

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Nutrient

Visible Symptoms

Possible Causes & Remedial Action

Nitrogen

Uniform pale colour to leaf and stem, with yellowing, especially of lower leaves. Feeble growth and lack of branching

Nitrogen is a ‘transient’ nutrient, meaning that it cannot be ‘stored’ in the soil for any length of time; it needs regular replenishment. Deficiency could be caused by excessive rainfall or watering, or regular over-cropping without addition of organic matter to the soil.

Phosphorus

Reduced growth, especially soon after seedling emergence. Often there is no other symptom, though some species show a purple coloration of older leaves.

Phosphate ions are negatively charged so are not held by negatively charged clay particles and can be leached by excessive rainfall or watering. Phosphate can bind strongly in an insoluble form in the presence of iron and aluminium sesquioxides in the soil. Phosphate shortage is a major limitation to plant growth worldwide. Organic phosphorus from bonemeal or hoof and horn may be added but this is very slow acting. For faster results the addition of superphosphate of lime is to be preferred

Potassium

Margins of older leaves scorched and curled, either in an upwards or downwards direction. Shoot tips are weak, sometimes with shrivelling. Poor flowering and poor subsequent fruit development

Potassium ions are positively charged and are held by the negatively charged clay particles and by organic matter. Most soils contain quite large amounts of potassium, though it may be held in an insoluble form, only being released slowly by weathering. When demand outstrips supply in intensive growing conditions the only remedy is to supplement with added inorganic soluble potassium salts (sulphate of potash). If a high magnesium content is present this can hinder potassium uptake by the plant.

Calcium

Cupping and burning of leaf tips with blackening of young leaves. ‘Blossom end rot’ in tomatoes, ‘bitter pit’ in apples and pears

Calcium deficiency can be caused by an irregular watering regime, especially in tomatoes, or a period of drought. Calcium ions are highly soluble and may be leached out of soils by high rainfall, leaving soils with a low pH (highly acid). A quicker acting remedy may be effected by the addition of calcium nitrate, and a longer term, more sustainable, solution is to lime the soil every third or fourth year.

Magnesium

A yellowing between the veins in older leaves (interveinal chlorosis) giving a marbled appearance.

There is usually sufficient magnesium in most soils, but non-soil composts or a high potassium feeding regime, such as that for tomatoes can lead to a deficiency. If either potassium or magnesium presence is excessively higher than the other, it can hinder the uptake of the lesser and cause deficiency. To redress the balance a solution of magnesium sulphate (Epsom salt) should be watered into the soil or compost.

Iron

Yellowing between the veins on older leaves and the production of pale yellow or nearly white young leaves

Iron becomes less soluble at higher pH (more alkaline) and more difficult for plant uptake (lime-induced chlorosis). A solution of iron sulphate or a proprietary sequestered iron compound will usually restore the balance. More likely to affect very acid loving (ericaceous) plants growing in soil with too high a pH.

Manganese

Yellowing between veins of young leaves, but may quickly spread to other older leaves

Usually occurs quite rarely. A solution of manganese sulphate or the addition of trace elements should remove the problem

Molybdenum

Rarely occurs but can affect cauliflowers grown in sandy soil. New leaves become progressively twisted and reduced until only the midrib remains (condition known as ‘whiptail’)

Element leached out of free-draining sandy soil. Solution of molybdenum sulphate or addition of trace elements.

Zinc

This is usually quite specific for certain plant species and difficult to detect without detailed analysis

Very rarely occurs. Add trace elements

Copper

Very dependent on plant species. New leaves become greyish-green, yellow and occasionally white

Very rare. Water with v. weak copper sulphate solution or add trace elements

Boron

Brittle tissues which crack easily. Death of growing point and production of side shoots

Can occur in brassicas, especially if affected by club root. Can also occur in beet causing ‘browning’ of the root colour. Add solution of borax or trace elements. More prevalent in sandy soils.

Sulphur

New leaves are a uniformly golden yellow and/or cupped and deformed. Foliage is frequently stiff and held erect.

Sulphur deficiency is quite rare, being usually confined to very free draining sandy soils. Sulphur in organic fertilisers may be used to correct deficiencies, but they are quite slow acting. An inorganic sulphate salt of ammonia, magnesium or iron will usually act more quickly, though they will cause increased soil acidity.

Chlorine

Wilting

Osmotic balance upset, very rare. Check first that plant not suffering from drought or excessive waterlogging, then check if the roots are being attacked by pest or disease. Add weak solution of potassium chloride if none of above.

The recognition of a nutrient deficiency (or, in some cases, toxicity) in a plant does not necessarily mean that the nutrient is not present in the soil; it could be present but conditions are not favourable for its assimilation into and use by the plant. So not just a recognition of nutrient deficiency in a plant, but also a knowledge of the possible causes for it, together with remedial action is useful to the gardener. The following table gives some general symptoms of nutrient deficiency, but it must be remembered that deficiencies of micronutrients are usually plant specific, as there is usually sufficient micronutrients present in most UK soils. The main cause of micronutrient deficiency and some macronutrient deficiency is by leaching of sandy soils by high rainfall

Table: Symptoms of Nutrient Deficiency

Nutrient Deficiencies

Deficiencies in ‘macronutrients’ are more likely to occur than those of ‘micronutrients’ A shortage of macronutrient is more likely to ‘mask’ a micronutrient deficiency. Any remedial action taken may be too late to effect a remedy in the crop plant currently growing, but improvements should show in a subsequent crop. Keeping the soil in good ‘heart’ by regular manuring, or addition of well rotted compost and crop-specific fertiliser should eliminate most problems entirely.