Tips for Fertilizing Vegetables

While well-rotted compost and farmyard manure applied regularly to a vegetable plot certainly help to maintain the fertility and health of the soil, crop yields can be increased considerably by the discreet use of fertilizers. Generally the best results are obtained from the application of so-called balanced fertilizers, in other words those that have nitrogen (N), phosphates (P) and potash (K) in their formulations. Nitrogen encourages leaf growth, phosphates aid root and seed development, whereas potash ensures healthy growth and at the same time improves vegetable flavor. Balanced fertilizers may be based entirely on inorganic ingredients, for example `Grow more', which has long been popular with vegetable growers. One hundred per cent organic formulations are available but usually at a higher price; these are slower acting but contain minor or trace elements not present in inorganic fertilizers. And then there are fertilizer mixtures on the markets with both organic and inorganic constituents.

It is at the beginning of the season when the winter dug soil is being broken down for seedbed or planting preparations that we get the best value from balanced fertilizer applications, worked in with a rake at 2 oz to the square yard (60 g per m2). For follow-up surface applications between the rows of growing crops, half the pre- sowing rate is sufficient. Granular or dry fertilizer formulations applied during the growing season are more effective and act more quickly when lightly hoed in and followed up with a watering when the weather is dry.

Leafy crops, brassicas in particular, sometimes need a tonic, especially in the spring or early summer to get them going. Nitrogen alone is suitable for the job. Here again the choice can be inorganic - i.e. sulphate of ammonia, nitro chalk or nitrate of soda, at no more than 1 or to the square yard (30 g per m2) around the plants .

Other straight fertilizers are super phosphate of lime, freely available, basic slag with its trace elements (not so easy to find these days), and sulphate of potash, sometimes used on its own when plants are making excessive amounts of leaf growth.

Foliar fertilizers, applied either as a spray or watered on to the foliage, are quick acting, some of the nutrients being taken up in part by the leaves, a useful emergency treatment which should be applied in the late evening during hot, dry weather in the summer.

While garden lime is not a fertilizer in the true sense of the word, the calcium it supplies enables the plants to make better use of other nutrients, particularly phosphates. Its application improves the texture of heavy clay soils, making them easier to work. Continual vegetable cropping, plus repeated applications of compost or farmyard manure, to make light and medium al, progressively more acid, a condition which slowly reduces yields in most crops, with the possible exception of potatoes. For continuous brassica growing, with its consequent risk of clubroot, the soil should he somewhere near or slightly below neutral pH 7. The degree of acidity or alkalinity in a soil can be determined by the use of a simple soil testing kit or pH meter. For soils below pH 6 apply 3 oz to the square yard (90 g per m2) of garden lime, but never before planting potatoes. And be particularly careful not to over-lime, as it can produce problems.