Organic Gardening:

How to use organic fertilisers

by Frann Leach

There are lots of organic fertilisers in use, but many of them come with no instructions. So how do you know what to do with them? Not every fertiliser is suitable for every situation, and it can be confusing for a beginner just starting out.

Your basic fertilising toolkit should really contain a good broad fertiliser such as blood, fish and bone, a bottle of liquid seaweed fertiliser to give a quick boost and for use as a foliar feed at half strength, plus comfrey liquid if you will be growing fruiting crops like tomatoes, courgettes (zucchini) or, indeed, fruit.

But if someone offers you something you've never used before, it helps to know what you can do with it. This table puts the when, where and how much of various organic fertilisers at your fingertips.

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

P

Q

R

S

T

U

V

W

X

Y

Z

Material	Notes	N	P	K	per sq. m/sq. yd
Animal hair	Slow to break down, a good slow-release source of nitrogen	2			250g/8 oz
Bark, composted	Contains little nutrient value, but high in humus. Particularly good as mulch.
Bone meal	Sometimes available as bone flour and crushed bones Good for light soils.	1	3	1	85g/3 oz. 112g/4 oz for fruit bushes
Bracken	Burn when green in a slow bonfire.			2	450g/1 lb
Calcified seaweed	Every 3 years		1	1	6 oz (trees 10 oz)
Chicken manure	Very strong manure that should be stored for several months before use. Useful as a compost activator.	2	2	2	25-50g
Compost	Can be used as a mulch 3-4" deep.	2	2	2	1 barrowload per 4.5m (15') row
Dolomite (magnesium limestone)*	Neutralising agent and to prevent magnesium deficiency.				113g/4 oz
Dolomite & gypsum*	Lightens heavy clay: Apply in spring and October/November at 340g/12 oz and then 85g/3 oz in following years.				250g/8 oz
Dried blood	Dissolve in 1 litre of water, standing for three days and stirring occasionally, or sprinkle round the plants and then with water with a fine rose and tease into the surface.	4	1		56g/2 oz
Farmyard manure (Well-rotted)	Excellent soil conditioner. High in nutrients and humus (from straw). Not for mulching.	2	1		140g/5 oz
Feathers	Not for use on clay. Dig in during autumn and winter.	2			140g/5 oz
Fish, blood and bone	Apply in early spring and repeat when crops are about half grown.	5	5	6	56g/2 oz
Fish meal	Very expensive.	2	3	1	85g/3 oz
Goat manure	Compost with straw.	2	2	2	50 kg/1 cwt
Green manures	See >separate table..
Hoof and horn	Add about 56g/2 oz to each bucketful of potting soil. Do not use on spring cabbage, spinach, Swiss chard or sprouting broccoli.	2	1		112 kg/4 oz
Spent hops	Soil improver. Little nutrient value but useful as humus source or mulch.				1-1.5 kg/2-3 lb
Horse manure	Only if mixed with straw, rather than wood shavings. Compost well first.	1	1	1	1 barrowload per 4.5m (15') row
Leaf mould	Soil conditioner. Beech and oak are best. Avoid evergreens. Can also be used as a mulch. Always rake aside in winter, to allow birds to find and eat pupating pests.			1	2.25 kg/5 lb
Leaves	A new garden full of raw subsoil can have up to 6 inches of raw, dead leaves spread on the surface and rotavated through the top 8 inches or so, which chops them and distributes them through the surface layer. Give two cultivations, and before the second one spread up to 450g (1 lb) a square yard of lime to correct acidity.
Lime* Do not mix with manure	Neutralising agent Quicklime must be slaked before use: 750 g/1.5 lb max. Hydrated lime: 112g/4 oz, 250 g/½ lb on heavy soil. Dolomited limestone: 500g/1 lb max Carbonated lime for light soils: 168-250 g/6-8 oz.	-	-	-	Depends on pH of soil
Manure and peat	Not suitable for organic gardening.
Municipal compost	May contain heavy metals and fragments of glass and plastic. Do not handle with bare hands.		1	1	1.35 kg/3 lb
Spent mushroom compost	Avoid compost made entirely from straw composted with chemical activators and no horse manure. Best composted first. Contains chalk, so not for use on alkaline soils.	1	1	1	1.35 kg/3 lb
Peat	Not suitable for organic gardening
Pig manure, rotted	Contains copper. Must be composted for at least 8 months before use, preferably with plenty of vegetable matter.	1	1	1	38 kg/0.75 cwt per 4.5m (15' row
Pigeon manure	Can be used moist as a compost activator.	2	2	2	250g/8 oz dried
Plant ash				2	500g/1 lb
Poultry manure	Makes an excellent compost activator. Best composted before use.	2	3	3	250g/8 oz
Rabbit droppings	Nutrient value improves when composted.	1	2	1	500g/1 lb dried
Rock phosphate	A slow-release source of phosphorus. One dressing will last at least 3 years.		3		8oz
Rock potash	Particularly useful for tomatoes, potatoes and gooseberries. Remains in the soil for about 3 years.			3	250g/8 oz
Sawdust	Used as a mulch around gooseberries and currants.
Seaweed	Very good soil conditioner containing valuable trace elements. Best dug in, as once it dries out, it becomes light enough to be blown away. Since it contains salt, it is best to stack it (with a porous cover, such as sacking, to prevent wind loss) and either wait for a good rainstorm, or soak it really thoroughly with a hosepipe before use (or use sparingly).
Seaweed meal	Use as a spring lawn tonic at 112g/4 oz. An excellent compost activator.	2	2	2	56g/2 oz
Sewage sludge	Use only digested sludge. Contains heavy metals - best used for ornamentals only. Use in early spring and again when crop is about half-grown. Can also be used at 3 parts to 1 part seaweed meal as an excellent compost activator. Can also be used on the lawn before the first spring mowing at 224 g/8 oz.	2	2	2	168 g/6 oz
Shoddy	Waste material from wool and cotton manufacturing. An excellent slow-release source of nitrogen and humus.	0.2 -15			500g/1 lb
Soot	Use only on neutral or alkaline soils. Old gardeners used to use this to 'darken' lighter soils to aid heat retention.	1
Wood ash	Must be stored very dry. The best ash comes from tree thinnings and fruit tree prunings, used as soon as it cools.			3	4 oz maximum
Wood chips, composted	Contain little nutrient value, but high in humus. Particularly good as mulch. As it robs nitrogen, it is wise to sprinkle some Fish, Blood & Bone on the surface before applying.
Worm compost	Use in potting compost and as a mulch.	2	2	2

* Do not mix any type of lime with manure; ammonia will be released and nitrogen lost.





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