The improvement of native agriculture in relation to population and public health / by Sir A. Daniel Hall.

  • Hall, A. Daniel (Alfred Daniel), Sir, 1864-1942.
Date:
1936
Catalogue details

Licence: In copyright

Credit: The improvement of native agriculture in relation to population and public health / by Sir A. Daniel Hall. Source: Wellcome Collection.

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    methods of restoring fertility on the soils of second quality, which are best under arable cultivation but can only grow cereals for sale. There it has become general to exchange the four-course or allied rotations, which have now become too costly in labour for the root crop, by an alternation of three or four years of grass and wild white clover, which in our climate is perhaps the most efficient gatherer of atmospheric nitrogen, with three or four successive cereal crops, for the growth of which little or no fertilizer nitrogen is then required, so considerable is the stock left behind by the clover and grass residues. This system of alternating a temporary ley, in which wild white clover plays a prominent part, with a short succession of cereal crops appears to have originated among the sheep farmers of the Border counties, but has become regular practice in the Midlands and south of England, where it has been found necessary to eliminate the turnip crop because of the labour involved. In this case the farmer is making use both of the nitrogen¬ collecting power of the wild white clover and of the further gain of nitrogen by Azotobacter working upon the basis of carbohydrate material left behind in the roots and stubble of the grass crop. In the other countries of western Europe we see at work similar methods of maintaining fertility. The rotations adopted always contain a leguminous crop; the constituents of the fodder crops and the residues of the saleable crops are restored to the soil by the intervention of animals and their conversion into farm-yard manure. It is a conservative system, the ultimate draught upon the soil is light, and there are recuperative periods when a crop like lucerne occupies the soil for some years. But the level of fertility thus maintained is not high, and the population that can be supported from the land is not dense. As I have discussed elsewhere,10 in western Europe about 2\ acres of cultivated land appear to be used in providing for one unit of population, even though in these countries a considerable proportion of extraneous fertility is imported as fertilizers or feeding-stuffs. Even in Den¬ mark, perhaps the most intensively cultivated area, the