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Organic Gardening:

N:P:K Analysis of common composting materials


Organic gardeners make use of a number of different fertilisers. However, because they are generally not bought in packets with an NPK analysis on the side, it's sometimes difficult to work out what each type should be used for. This is difficult if you are trying to follow a book with instructions to apply a fertiliser with a particular balance of nutrients.

Organic fertilisers generally are much more holistic in their effect, and provide a much broader spectrum of both nutrition and humus than the conventional products available in stores, and there is no reason to go back to artificial feeds when there is such a variety of organic alternatives available. Many organic products are slower to come into effect, but this means you get a sort of "timed release" effect which is not available to the gardener using conventional products.

This table gives a typical analysis of Nitrogen, Phosphorus and Potassium content of a number of different organic products, together with an idea of their speed of activity.

Type Action Nitrogen (N) Phosphorus (P) Potash (K)
Dried blood Quick 9-13 0.80 -
Blood, fish & bone Medium 5.1 5 6.5
Bone meal Slow 0.3-4.6 14.1-33.2 1.0
Chicken compost, deep litter Medium 0.80 0.55 0.48
Comfrey compost   0.77 0.29 0.92
Cow dung, strawy   0.54 0.31 0.67
Cow dung, well-rotted   0.59 0.45 0.49
Farmyard manure Slow 0.65 0.23 0.32
Fish meal Quick 6.3-8.9 6.0-8.9 1.0
Guano Quick 15 10 7
Spent hops Slow 4 2  
Hoof & horn meal Slow 6.5-13.2 0.20 -
Kainit Slow     13
Mushroom compost   0.80 0.63 0.67
Rape meal Medium 5 2 6
Seaweed meal Medium 2.88 0.22 2.29
Seaweed, dried Slow 2.88 0.22 2.29
Urine-activated compost   0.80 0.29 0.41
Wool shoddy Slow 12    

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Article ©2004 Frann Leach. All rights reserved.

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