Fertilizer Types and What They Contain

types of fertilizers

Fertilizer Types and Their Contents

Each one of the essential nutrients — nitrogen, phosphorus (in phosphate) and potassium (in potash) —can be purchased separately as so-called ‘straight’ fertilizers, or in balanced mixtures known as ‘compound’ or ‘general’ fertilizers. The latter type generally include the most important trace elements.

Below is a table detailing the nutrient content of each one, together with application method and special features.





Magnesium sulphate
(Epsom Salts)

10% magnesium sulphur Top dressing Effective against chlorosis
Nitrate of Ammonia 35% nitrogen Liquid feed Do not mix with lime
Nitrate of soda
(sodium nitrate)
16% nitrogen; trace elements Top dressing Fast acting but quickly washed out of the soil. Keep off foliage
Nitro chalk 16% nitrogen; calcium Top dressing Contains 48% lime. Long lasting, fast-acting; useful on acid soils. Can be used to aid rotting of compost.
Potassium nitrate 12-14% nitrogen; 44-46% potash Top dressing / liquid feed A general spring fertilizer. Impure Chilean potash nitrate contains only 15% K2O
Sulphate of ammonia 21% nitrogen; sulphur Top dressing Best source of N, but makes soil more acid. Do not mix with lime. Fast-acting.
Sulphate of iron Iron; sulphur Top dressing Effective against iron-induced chlorosis. Acidifies the soil
Sulphate of potash 48% potash Base or top dressing Best general source of potash. Fast-acting for flowers and fruit. Acidifies the soil
Superphosphate 13-20% phosphate Base dressing Best source of phosphates. Keep off delicate leaves. Do not mix with sodium nitrate
Urea 46% nitrogen Liquid / foliar feed Very rich source of N. Apply in spring



2-5% nitrogen; 20-30% phosphate; calcium

Base or top dressing

Slow-release fertilizer; apply in spring or autumn. Contains lime. Ensure it is sterilized

Dried blood 10-13% nitrogen Top dressing / liquid feed Fairly fast-acting. Apply in late spring or summer. Ideal for leaf vegetables
Fish meal 6-10% nitrogen; 5-12% phosphate; 1-2% potash Base dressing Fairly slow-release; apply during spring cultivation, one spade’s depth.
Hoof and horn 7-15% nitrogen; 1-10% phosphate; calcium Base dressing Fairly slow-release, though speed depends on fineness of grinding. Apply in spring
Wood ash 2-9% potash Top dressing Must be kept dry to retain potash. Young wood produces the richest ash. Not for chalky soil



7% nitrogen; 7% phosphate; 7% potash Base or top dressing Good general-purpose fertilizer. Apply in spring. Now available also in liquid form
John Innes base 5% nitrogen; 7% phosphate; 10% potash Base or top dressing Contains hoof and horn; slow-release of N. Used mainly in potting mixtures
Rose fertilizer 5% nitrogen; 6% phosphate; 12% potash; iron; magnesium Top dressing Fairly fast-acting. apply in summer. Specially formulated for roses, but suitable for others
Sequestine tonic Magnesium; manganese; iron Top dressing Cures yellowing. May include other trace elements
Tomato fertilizer 6% nitrogen; 5% phosphate; 9% potash Liquid feed Used as weekly feed throughout the growing period to promote a high yield. Ideal for growing bags.

Nutrient Deficiency Symptoms

Use the above table to assist with correcting the following plant deficiency symptoms:

Nitrogen deficiency is indicated by poor, stunted growth with pale leaves and weak stems. Leaves often turn orange, red or purplish and may fall prematurely. Fruit trees and vegetables are most commonly affected.

Potassium deficiency is indicated by brown scorching around the edges of the leaves. Flowers may be dull and sparse, and fruit yield may be low and of poor quality. Tissues are soft and more prone to pests and diseases.

Magnesium deficiency is indicated by yellow patches between the leaf veins which later turn brown. The affected leaves may wither. Roses and tomatoes are often affected. Magnesium sulphate (Epsom salts) spray is the best cure.

Manganese deficiency is indicated by yellowing between the veins of older leaves. Leaf edges may become slightly in-curled and brown. Many types of plant may be affected occasionally. Apply a sequestrine plant tonic.

28. October 2010 by Dave Pinkney
Categories: Garden Management, Manures and Fertilisers | Tags: , , | Comments Off on Fertilizer Types and What They Contain


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