Keeping your vegetables in strict rotation; GARDEN RULES.
Each autumn when I stow my beans sticks away for another year, I am mindful that growing vegetables in the same place is not generally advised because this encourages soil-borne pests and diseases.
But since visiting a friend's allotment I'm not so sure, at least for the cultivation of runner beans.
His is no ordinary allotment with a rusting shed in one corner and a greenhouse with ragged plastic sheeting instead of glass, but a showpiece producing a variety of vegetables to make the mouth water.
The focal point is metal scaffolding poles no different to those used as platforms for house-builders except that in this case they support his runner beans. Since the poles were soldered together there is no way the edifice could be dismantled annually which could only mean the beans are always grown in the same place.
In fact, the structure has been in situ for 30 years, supporting my friend's runner beans without any apparent problems with soil-borne diseases or decline in quality and yield. But he feeds them massively, every autumn opening up a trench beneath the twin rows of scaffolding poles and filling it with every scrap of vegetable and plant waste.
For seven months of the year the trench is a steaming compost heap until May when it is back filled with earth excavated the previous autumn which having been exposed to the elements all winter disposes of soil-borne diseases and pests. For good measure, slug pellets are scattered along the trench.
This flies in the face of perceived wisdom which states that crop rotation, whereby a crop does not occupy the same ground for three years running, is essential to reduce disease and make the best possible use of plant foods in the soil.
The theory of plant rotation is based on the fact that plants differ in their food requirements, some needing more of one chemical and some of another. Members of the cabbage family require heavy supplies of nitrogen, whereas root crops, such as carrots, parsnips, turnips and beetroot, need less nitrogen but more phosphate.
YOUR TO DO LIST | Clay soils are rich in nutrients but need liming to make these more readily available. | Nutrients are quickly washed out of sandy soils which need an annual application of a balanced fertiliser like Growmore. | Pot up parsley and bring inside for fresh winter foliage.
| Prune berry fruits after harvesting, cutting out old stems and tying in new ones.
| Remove one third of old branches from mature blackcurrants.
It follows therefore that a plot prepared for brassicas with plenty of farmyard manure or equivalent rich in nitrogen will, once the cabbage has been harvested, carry sufficient residual phosphate for a crop of carrots the following year.
The general practice is to lime one third of the vegetable garden in autumn where brassicas are to be grown. The area reserved for root crops receives only general fertilizer while the potato patch is manured but not limed because that causes scab.
The following year brassicas are grown where the potatoes were, the potatoes where the roots were, and root crops follow the brassicas.
Some salad crops can be grown before brassicas are planted while peas and beans may be grown in the root crop plot so long as a trench is taken out first and manured which explains my friend's continuing success.
Onions are frequently grown in the same ground year after year, which gives good results provided the soil is well manured and white rot fungus is avoided.
While not everyone can stick to the strict rotation of crops, on balance some rotation is recommended for cultivating healthy plants and making the most effective and economical use of fertilisers.
The theory of plant rotation is based on the fact that plants differ in their food requirements, some needing more of one chemical and some of another
A crop of runner beans