Base Dressing or Top Dressing? Usually you will need to get the levels right before sowing or planting. This is called a base dressing, and should be worked into the top 6 to 8 inches of soil. Sometimes you will just need to top up during the year. This is called a top dressing, and is hoed into the surface of the soil, or sometimes just left on the surface without hoeing in. Some plants, like lawns for example, can only be top dressed Timing Occasionally you might want to boost a particular plant food. For example, Potash just before flowering will usually give extra colour, or Nitrogen in spring will give a boost to growth. These will probably be a top dressings. There is not much point in using fertilisers just before winter, because plants are not growing then, and heavy rainfall will wash the plant foods out of the soil before they can be used. You can also cause damage by making the plants too soft, and not able to withstand the winter frosts. You should also avoid using fertilisers in periods of low temperature, drought or exceptionally high rainfall as they will be wasted. Compatibility With Lime Some fertilisers react badly with lime (see fertiliser lists), but even with those fertilisers that are compatible with lime, it is a wise precaution to leave at least 4 and preferably 6 weeks between the use of lime and fertilisers. If this causes timing problems, it is probably best to get the lime right first, then use the fertilisers as a top dressing 4 to 6 weeks later. Apply With Care It is possible to overdose your plants on fertilisers quite easily, so any dressing more than 2.5 oz per square yard should be split into two or more doses using less than 2.5 oz each time. With highly concentrated types like Sulphate of Ammonia it would be safer to use less than 2 oz per dose. If you find it hard to apply small amounts of fertiliser evenly over an area, try bulking it up with dry sand. Provided that you mix it thoroughly, the greater volume should make it much easier to spread easily.

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How plants get their food | Nitrogen | Phosphate | Potash | Brand name fertilisers and mixtures | When to use fertilisers | Food values of different manures and fertilisers

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