Quick guide to fertilisers – fertiliser rotation

Autumn Spring Annually
1st year
Manure General fertiliser,
eg Growmore *
Sulphate of ammonia
For a quick nitrogen boost if a soil test shows low nitrogen.
Fish, blood and bone
For a feed booster during the growing season.
When planting trees or shrubs, including roses, and as spring feed for same.
2nd year
Lime (but not where potatoes are to be planted) As above As above
3rd year
Omit manure and lime As above As above

* As an alternative to Growmore, for potatoes, tomatoes and courgettes, use a mix of 1 part superphosphate to 4 parts potash, or pelleted chicken manure which also has the advantage of being organic.

Note: It is always advisable not to use manure at the same time as fertilisers otherwise one negates the other. Make sure there is at least a three month gap between manuring and fertilising.

What is it? How to use it?

Bonemeal A mixture of crushed and coarsely ground bones used as an organic slow-release fertiliser.
High in phosphate and is suitable for all plants including trees, shrubs, roses, fruit and vegetables.
Traditionally used for encouraging strong root growth at planting or in the spring to get plants off to a
good start to the season. Use 70g-135g per square metre, applied evenly and worked
into the top 50-70cm of soil.
Calcified seaweed Seaweed contains several useful plant nutrients, including nitrogen, potassium, phosphate and magnesium. Encourages beneficial soil bacteria, helps improve heavy soil structure and neutralises acid soils (do not use with acid loving plants). An excellent feed for onions and leeks, used prior to planting.
Fish, blood and bone Made from the by-product of fish that have been processed, this is a traditional organic fertiliser that contains the three major nutrients for strong and healthy plant growth: nitrogen, phosphate and potash. Nitrogen encourages strong growth and healthy rich green foliage, whilst the slow release of phosphate promotes vigorous root growth. The added potash promotes flower colour and improves ripening of fruit and vegetables.
Garden lime Lime raises soil pH by reducing its acidity and is usually added as ground limestone, commonly called 'garden lime'. The active ingredient is calcium carbonate. Calcified seaweed and ground chalk are other forms of calcium carbonate available to gardeners. Lime is usually added in winter for annual crops, such as vegetables, just prior to digging, as the lime can take effect over the winter months and will not damage young growth. Note: Before adding lime, check your soil pH to see how much (if any) you need to add. The Royal Horticultural Society offers full information about the use of garden lime and testing soil pH. Click here to be taken to the page: RHS Lime and Liming.
Growmore Growmore, probably the most popular compound fertiliser, was first formulated as part of the Dig For Victory campaign in World War II (1939-45) - hence its full name National Growmore. It's a multi-purpose plant food with an even balance of nitrogen, phosphorus and potassium or potash. Apply 140g per square metre onto the soil 7 to 10 days before planting or sowing and fork well in. For salad crops use half the quantity. This should give sufficient nutrients for 6 to 8 weeks. Can also be applied to the soil surface once a month to keep your plants well fed throughout the growing season.
Scatter 70g per square metre onto the soil and lightly fork or hoe in.
Potash Potash is the common name for fertiliser containing potassium. The name derives from metal pots that were once used to store wood ash, in readiness for use as a fertiliser. It's a fast acting source of potassium to help the development of healthy fruit and flowers. Ideal for feeding all types of fruit trees, bushes and flowers to help them become more weather and disease resistant.
Use about 35g per square metre from March to end of August, every 4 to 6 weeks.
Sulphate of ammonia A rich, fast acting source of nitrogen which promotes above-the-ground growth and rich, green foliage. Particularly beneficial in leafy vegetable and salad crops such as brassicas, lettuce, spinach, rhubarb and leeks. It is made by a commercial process that causes ammonia to react with sulphuric acid. When added to water it becomes soluble and thus is readily taken up by plants, with effects being noticed in under 10 days. Since it is highly soluble in water it also means that it leeches from the soil easily, thus requiring regular applications. Apply during the growing period from March to August at 4 to 6 week intervals. Use about 35g per square metre. Sulphate of Ammonia is not considered for use by organic growers
Superphosphate Produced by the action of concentrated sulphuric acid on powdered phosphate rock. Encourages strong root growth and healthy plants. Fruit, root and seed crops will produce higher yields and ripening will be improved. Apply evenly at the recommended rates, then hoe or fork into the top surface of the soil and,
if dry, water well for maximum benefits.

Want to know more about using fertilisers on an allotment?
National Vegetable Society: NVS Understanding Fertilisers
Royal Horticultural Society: RHS Advice about Fertilisers