A short guide to there use: This page outlines the main categories e.g. whether organic or inorganic, suitable as a base or top dressing, together with details of the main plant requirements (nitrogen, phosphate, potash). At the end of the page are details of specific fertilisers available at highly competitive prices to members of the Society from the Store, The Pleasance, Dover House Road every Sunday morning, 10.00 am to 12 noon.

Organic fertilisers are those that originate from living organisms (plants or animals). They release nutrients slowly and may also improve soil texture. They contain trace elements as well as major nutrients but are unpredictable in what they release. If bought, they may be expensive if they are bulky and weigh heavily, but the cheapest source is always your own compost heap. They maintain long-term soil fertility and are used to prepare soil for planting shrubs and slow-growing plants. Examples include: bone meal; fish , blood and bone; horse manure and Country Natural Compost.

Inorganic fertilisers are exact in their contents and come either from quarried materials e.g. rock phosphate, limestone and Epsom salts (magnesium sulphate) or are manufactured chemically e.g. Growmore, nitrochalk and superphosphates. (The latter are not acceptable to strict organic gardeners.) Inorganic fertilisers can quickly supply a particular deficiency e.g. ammonium sulphate will supply nitrogen. Proprietary fertilisers have different N:P:K ratios (see below) for different plants e.g Cactus fertiliser has a ratio of 8:34:32. The disadvantages of inorganic fertilisers are that they may leach (drain) rapidly from soil after rain, and can damage plants if applied too liberally.

Base dressings are dug into the soil at root depth when preparing it for planting. All slow-release organic fertilisers are suitable, as are the newer (expensive) inorganic fertilisers in a resin coating e.g. Osmacote and Chempak’s Summerlong.

Top dressings are applied on the surface around established plants. They are best applied under a mulch or watered in thoroughly to distribute the fertiliser equally.

Major Plant Requirements (N:P:K)

  • Nitrogen (N): essential for growth and dark green foliage; apply as base or top dressing; particularly to young plants and sparingly to mature plants
  • Phosphate (P2O5): essential for good root development; promotes ripening of fruits and seeds; apply as base dressing or top dressing forked in to reach the roots
  • Potash (K2O): essential for production of flowers and fruits; promotes healthy growth and resistance to frost and fungal diseases; apply as base or top dressing; slow to leach away and therefore apply at any time of year

As well as a large number of commonly used garden products (e.g. seed and potting composts, Garotta, lawn feed, insecticides, weed killers, slug pellets, etc.), the Store stocks the following loose fertilisers.

  • Bone meal: organic fertiliser supplying phosphate and some nitrogen; acts slowly; do not use on acid-loving plants (use 100-125 g per sq m or 3-4 oz per sq yd)
  • Fish, blood and bone meal: as above but quicker acting with more nitrogen; apply before planting or sowing seeds or as a top dressing during growth (use 50-200 g per sq m or 2-7 oz per sq yd)
  • Growmore: (N:P:K = 7:7:7) suitable inorganic all-purpose fertiliser (use 50-125 g per sq m or 2-4 oz per sq yd)
  • Lime: inorganic; although supplying calcium its importance is in neutralising soil acidity; in turning soils alkaline it protects brassicas against club root fungus; it improves the soil texture of heavy clays
  • Nitrochalk: quick-acting inorganic nitrogenous fertiliser containing lime and therefore useful to combat acidity; use as top dressing in summer but avoid excess (use about 25 g per sq m or ½-1 oz per sq yd)
  • Rose fertiliser: made to Tonk’s formula specifically for roses (use 50-125 g per sq m or 2-4 oz per sq yd)
  • Sulphate of ammonia: quick-acting inorganic nitrogenous fertiliser; boosts growth of leafy vegetables (cabbages, lettuces, etc.) (use about 25 g per sq m or ½-1 oz per sq yd)
  • Sulphate of potash: inorganic fertiliser supplying potash (see over page); essential for tomatoes (use about 25 g per sq m or ½-1 oz per sq yd)
  • Superphosphate of lime: neutral inorganic fertiliser supplying phosphate (see over page) (use 50-125 g per sq m or 2-4 oz per sq yd)

A small 150 g yogurt carton holds about 200g (7oz) fertiliser. NB Chemical fertilisers should always be used with great care