It is important to understand that all vegetables require a supply of nutrients. Of these the most important are nitrogen, phosphate and potash.
The main questions to ask are:
i) What are the best sources of these nutrients?
ii) In what quantity are they required?
iii) When should they be applied?
Nitrogen promotes vigorous dark-green growth in vegetables, and is of greatest benefit to all green crops and other leafy vegetables e.g. lettuce, celery and spinach.
Sources of n
Inorganic – Sulphate of ammonia Contains 15-23% N
Nitro chalk
Nitrate of soda
Organic – Dried blood
Hoof & horn
Farmyard manure
Quick-acting.
Gives a steady supply of N throughout the season.
Helps soil structure and water retention as well.
Sulphate of ammonia and nitrate of soda are usually applied at about 33g/sq.m (1 oz/sq.yd) either before sowing, or 10-14 days after sowing or planting, or during the growing period of the plant.
Phosphate stimulates the development of seedlings by encouraging a fibrous root system. It hastens maturity and increases yields – particularly of root crops.
Sources of p
Inorganic – Superphosphate
Organic – Bone meal Use sterilized bone meal
Superphosphate may be raked into the seed bed before sowing, usually at a rate of 50g/sq.m (1 ½ oz/sq.yd).
Potash maintains balanced growth in vegetables and helps plants resist adverse conditions e.g. poor light, shallow soil and severe winter weather.
Source of k note
Inorganic – Sulphate of potash
Muriate of potash Not equally suitable
for all vegetables.
Organic – Manures e.g. farmyard manure
The normal rate of application is around 33g/sq.m (1 oz/sq.yd).
Many of the compound fertilisers which contain N, P and K can be used in the vegetable garden, e.g. Growmore. A general mix which can be used as a base dressing colild include:
1.8kg (4 lbs) – Sulphate of ammonia 2.2kg (5 lbs) – Superphosphate V 0.9kg (2 lbs) – Sulphate of potash
These fertilisers should be raked in well a fortnight before sowing or planting, at the rate of 100g/sq.m (3 oz/sq.yd).
There are a number of proprietary liquid feeds which can be watered on during the growing season. These give speedy results.
Liming
Continual cropping, and the addition of compost and manures, may make the soil rather acid. To counteract this apply a dusting of lime in winter – 106g/sq.m (3 ¼ oz/sq.yd). Avoid over-liming, as this will not help growth. One can test the pH by using a proprietory soil-testing kit.
pH Crop/soil acidity tolerance
7.0 asparagus, radish
6.5 cauliflower, spinach
6.0 lettuce, leek, onion, parsnip
Critical levels of tolerance
5.8 beans, peas, brassica, carrot, celery / 5.0 cucumber, marrow, tomato, sweetcorn
Some soils are naturally free from particles of chalk or limestone, and the local flora will probably include heather, rhododendrons and bilberries. These soils are likely to benefit from the use of lime in the vegetable garden.
In other parts of the country, the Salisbury Plain and the Mendips for instance, -much of the mineral soil is composed of fragments of (CaCO2) – the chalk/limestone group which neutralize acidity and make soil alkaline (pH over 7). Some plants do not cope well with high pH conditions and their leaves may become golden or ivory-colored in the absence of the essential chlorphyll (green) structures. Such plants’ decline rather than thrive.
