386 THE POPULAR SCIENCE MONTHLY 



panying rise of salts. The governing principle is that drainage must 

 accompany irrigation. Even 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 pos- 

 sibility appears to be to take a comparatively 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 

 minimize 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 fertilizers under these conditions; 

 both tend to prevent the reaction of the soil becoming alkaline, and the 

 calcium salts of the superphosphate minimize the injurious effects of 

 the sodium salts that naturally accumulate in the land. On the other 

 hand, nitrate of soda is a dangerous fertilizer. 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 man- 

 golds 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 reclamation as it occurs in 

 northwestern Europe. There are two main types of land that have 

 hitherto been left waste, the peaty and the sandy areas. Of the peaty 



