Growing Food: A Guide to Food Production

Applying Fertiliser
There are four main ways to ensure that most of the fertiliser is used by the plant:

Broadcasting The fertiliser is spread, or sprayed if in liquid form, on to the

soil surface, the seedbed, before planting and then worked

into the soil with a hoe, rake or harrows. This is a quick

method, but much of the fertiliser is lost to weeds or to

leaching before the crop can utilise it.

Placement The fertiliser is put in the soil together with the seed, either

manually or by machine (a combine seed drill). The fertiliser

should never be in contact with the seed, but should be

placed either on one or both sides of the seed and/or about

2.5 cm below it. This is a much more precise method than

broadcasting, but slower. It is very often the best method to

use.

Top dressing

is very efficient but also very time consuming.

Foliar

application

Residual Value of Fertilisers
Fertiliser, and lime, which is applied to a crop is usually not completely used up by that
crop. A residual value of fertiliser or lime is then available for the following crop.
Potash is mostly used up after two crops, while phosphate can remain for three or
four. Nitrogen is not usually carried over in this way, but is rapidly either used by plants
or leached out of reach of plant roots. This is just one of the many factors to consider

For example, legumes and cereals are often planted after potatoes so that they
benefit from the large amount of fertiliser that is often given to potatoes.
The value of land sold or rented may increase if it has a high content of residual
fertiliser.

The fertiliser, normally N, either liquid or solid, is applied

grassland are very often top-dressed with nitrogen in the

directly on to the growing crop. Winter sown crops and

spring. Small-scale farmers and gardeners often place the

fertiliser by hand around individual plants and trees, which

The fertiliser can be applied together with irrigation water, a

technique suitable for dry fertilisers, ammonia, liquid com-

pound fertilisers and gypsum. But foliar sprays, as supplied

by overhead sprinkler systems, are only suitable for small

quantities of fertilisers because leaves are damaged by

high concentrations of salts. Normally trace elements rather

than major elements are applied this way; if large amounts

of fertiliser are to be applied, surface (flood) irrigation is

normally more suitable.

GROWING FOOD – THE FOOD PRODUCTION HANDBOOK 35

1.

2.

3.

4.

when planning a crop rotation, discussed further in 1Ha. “Rotation”, page 65.