Trace element deficiencies
Many organic gardeners are convinced that gardencures all . However, the evidence obtained so far indicates that cures of apparent diseases are really a matter of the compost ending trace element deficiencies. The compost supplies the very small amounts needed by plants of these essential minerals in a form that is readily available to their roots. It is very easy for a non-expert to mistake a trace element shortage for a virus attack.
The commonest of all the trace element deficiencies is magnesium deficiency. Gardeners who have fed their tomatoes andyear after year with potassium fertilizers can easily ‘lock’ their magnesium out of the reach of plant roots, which shows in the leaves turning yellow while the veins stay green.
One remedy for magnesium deficiency is to water with 60 g (2 oz) of Epsom Salts (magnesium sulphate) dissolved in 9 L (2 gal) of water per 3.3 sq m (4 sq yd) of, as soon as the trouble begins to show.
Another remedy is to spread 0.45 kg (1 lb) per sq m (sq yd) of ground dolomite limestone on the surface of the soil and dig it in during the winter. This dolomite is about half-and-half calcium and magnesium carbonates, and it will last in the soil for many years. It is much better to use dolomite limestone than Epsom Salts, provided that your soil is not already very alkaline.
The other area of the garden where you are likely to have trouble with trace element deficiency is the raspberry bed, for, whenever you cut out the fruited canes and burn them, you are taking away magnesium. The deterioration this causes may lead you to think your fruit have caught a virus disease and you would probably mistakenly dig up the bed and destroy the canes.
Try the Epsom Salts trick if you find that the leaves have yellow or red patches and green veins, and see if they are all right next year. Otherwise dig in dolomite when you turn under the mulch of lawn-mowings.
You can also dig in dolomite together with garden compost or even manure without problems. If you think your tomatoes are suffering from a virus disease, it is worthwhile digging in 0.45 kg (1 lb) of ground dolomite per sq m (sq yd) to ‘unlock’ your soil, which may well be suffering from too many chemical fertilizers, or have been ruined by the horticultural hypochondria that makes many organic gardeners pile on dried blood, bonemeal, fishmeal and anything else organic that they can find.
Dolomite is available in Britain, though it may take some tracking down, but it is widely used in Europe where there are many associations of organic gardeners.