IX.] CAUSES OF STERILITY 283 



fair crop of dineba (grass), 2 feet high, can be grown ; 

 with 1 per cent, it attains its full height of 4 feet, and 

 sells as a standing crop at from 20s. to 25s. per acre. 

 For ' berseem,' or clover, the percentage of salt should 

 not exceed h, and about the same for ' sabaini (quick- 

 growing or seventy-day) rice.' " Much, however, depends 

 upon the relations between water supply and evapora- 

 tion, as to the amount of salt in a soil which would be 

 tolerable to vegetation. From time to time cases occur 

 in this country of crops being destroyed, and land 

 rendered sterile by the incursion of sea water ; the effect 

 is not always apparent at first, though sea water contains 

 as much as 27 per cent, of sodium chloride and 05 per 

 cent, of other soluble salts, but the permanent pasture 

 becomes seriously injured, and for two or three years 

 even the arable land yields very indifferent crops. 

 Dymond has attributed this after-effect to the injurious 

 action of the sea water on the texture of the soil, due 

 to the attack of the sodium chloride upon the double 

 silicates of the soil, lime in particular being displaced 

 by soda. The result is the deflocculation of the clay, 

 which will not settle down for many weeks when sus- 

 pended in water. The sodium chloride of the sea water 

 would also interact with any calcium carbonate in the 

 soil, giving rise to sodium carbonate, the deflocculating 

 effect of which upon the clay has already been noticed. 

 Biological effects may also be surmised : it is always 

 seen that the earth worms are killed in the land which 

 has been flooded with sea water, and in view of the 

 known unfavourable effect of chlorides on nitrification, 

 it is possible that the rate of production of nitrates in 

 the inundated soil is seriously lessened. 



