This section is from the book "Commercial Gardening Vol4", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
For over three hundred years market gardeners, or maratchers, in the neighbourhood of Paris and other parts of France have practised a wonderful system of cultivation, by means of which they succeed in obtaining several large crops of salads and vegetables from a comparatively small patch of ground in the course of the year. Notwithstanding the improvements in greenhouse structures and heating apparatus the French gardener still continues to grow his Lettuces, Carrots, Cauliflowers, Radishes, Endives, Turnips, and Melons in the same way as his forefathers, and in many cases the mysteries of the art have been transmitted from father to son for several generations. Even now, when one fears that the almost universal adoption of the motor car will render it more and more difficult to obtain manure easily and at a reasonable rate, there seems to be no abatement in the number of gardens, nor in the amount of produce from them. While it is, of course, possible that motor cars will interfere to a certain extent with the massing of manure in the large cities, it may be taken for granted that there will be no appreciable reduction in the number of horses as a whole, either in France, in the United Kingdom, or in Germany. What is, however, likely to happen is that the manure will be more widely distributed throughout the country, and provincial growers may have as good an opportunity of obtaining large supplies as their brethren have hitherto had in the neighbourhood of large cities like London, and Paris, and Berlin. But good manure and plenty of it is one of the first essentials wherever the French system of intensive cultivation is to be practised.
In many quarters there is an impression that even if manure should become scarce its place can be easily taken by hot water. This is a delusion, and one likely to prove costly to those who rely upon it. In the first place, the great advantage of having plenty of manure is that the beds can be made in different parts of the garden year after year, and even during each season of growth, without one bed interfering with another, or the crops upon it. Whereas, if hot water is used, the pipes and structures are fixtures in one particular spot, and cannot be interfered with or moved from place to place with ease. And, again, to secure anything like a reasonable minimum output on commercial lines, far more glass would have to be used with hot-water apparatus than is necessary under the true French system, where only manure, lights and frames, and bell glasses are used. Perhaps these facts will appear more forcible from a comparison between the material required to cultivate a 2-ac. French garden and a similar area of ground under glass in the usual way.
900 lights (for 300 frames).........
20 per cent allowance for pathways
3000 cloches ...
20 per cent allowance for pathways
Total space covered with glass
Total space uncovered but useful for other crops
A.rea of 2 ac. ... • • • ... ... ..
It will thus be seen that when every light and every cloche is in use, and making an allowance for pathways, only 2860 sq. yd. - or less than one-third of the whole area - is covered with glass, most of the remaining two-thirds being available for other successional crops. And it must be remembered that some of the ground which is open one season will be covered with cloches and frames the next, so that a perfect rotation of crops and a thorough sweetening and "sterilizing" of the soil by exposure to the weather takes place in regular order.