642 TRANSACTIONS OF SECTION M. 
by evaporation of the soluble salts in the surface layer until plants refuse to 
grow. The annual cutting off of the cotton crop in Egypt as the water-table 
rises with the advance of the Nile flood affords a good example of asphyxiation, 
but in the neighbourhood of irrigation canals we also find many examples of 
sterility due both to the high water-table and an accompanying rise of salts. 
The governing principle is that drainage must accompany irrigation. EHven 
if free from salts at the outset the land must accumulate them by the mere 
evaporation of natural waters, and they will rise to the surface where they 
exert their worst effect upon vegetation, unless from time to time there is 
actual washing through the soil and removal of the water charged with salt. 
Without drainage the greater the quantity of water used the greater the 
eventual damage to the soil, for thereby the subsoil water-table carrying the 
salts is lifted nearer to the surface. With a properly designed irrigation system 
the danger of salting ought not to occur; there are, however, many tracts of 
land where the supply of water is too limited to justify an expensive scheme 
of irrigation channels with corresponding drainage ditches at a lower level. 
Take the case of a single farmer with some water from an artesian well at 
his disposal, with perhaps little rainfall, with land subject to alkali, and no 
considerable natural fall for drainage. If he merely grades the land and waters 
it, sterility rapidly sets in; the only possibility appears to be to take a com- 
paratively limited area and to cut out drainage ditches or tile drains 4 or 
5 feet below the surface, even if they have to be led into a merely local 
hollow that can be abandoned to salt. The bed thus established must then 
be watered at any cost until there is a flow in the drains, after which the 
surface is immediately cultivated and the crop sown. ‘There should be no 
further application of water until the crop covers the land, the use of water 
must be kept to a minimum, and by the ordinary methods of dry cultivation 
evaporation must be allowed only through the crop, not merely to save water 
but to prevent any rise of salt. With a loose surface and wind-breaks to 
minimise evaporation it has thus proved possible to grow valuable crops even 
on dangerously alkaline land. Superphosphate and sulphate of ammonia have 
proved to be useful fertilisers under these conditions; both tend to prevent 
the reaction of the soil becoming alkaline, and the calcium salts of the super- 
phosphate minimise the injurious effects of the sodium salts that naturally 
accumulate in the land. On the other hand, nitvate of soda is a dangerous 
fertiliser. Attempts have been made to reduce the salts in the land by the 
growth of certain crops which take up a large proportion of mineral matter, 
but I have not been able to ascertain that much good can be thus effected. 
Sugar-beet and mangolds do appreciably reduce the salt content, but are hardly 
valuable enough to pay for such special cultivation and the limited irrigation- 
water; the best thing appears to be to grow salt-bush on the non-irrigated 
margin of such areas, if only to prevent the efflorescent salts from blowing on 
to the cultivated portion. 
Let us now turn to the problem of land réclamation as it occurs in North- 
Western Europe. There are two main types of land that have hitherto been left 
waste, the peaty and the sandy areas. Of the peaty areas we can distinguish 
again between the low-lying moors bordering the lower courses of the great 
rivers ; for example, in England near the mouth of the Trent, and the upland peat- 
bogs of which Ireland furnishes so many examples. They have these features 
in common—an excess of water, a deficiency of mineral salts, and, particularly 
in the upland bogs, a strongly acid reaction; but they possess great potential 
wealth in their richness in nitrogenous organic matter. It is in Germany and 
Holland that the methods of bringing into cultivation these moors have been 
most completely worked out; in Germany, for example, it is estimated that 
there are about five million acres of moorland, of which about 10 per cent. is 
now under cultivation. The reclamation process must begin by drainage, which 
may be carried out by open ditches, but is most satisfactorily effected by pipes, 
despite the greater cost. The water-table must be kept some 3 feet below the 
surface. In districts which afford a market for peat, as, for example, on the 
Teufelsmoor near Bremen, the reclamation often begins by cutting out the 
peat, the lower layer of firm peat being won, dried, and sold for fuel. The 
upper spongy peat can be used for litter, but some part at least must be thrown 
