Soils — fertilizers. 3l7 



The proportion of sulphate decreased with the depth at which the water was 

 obtained. 



The proportion of ions in the deep water from two fields, one old and the 

 other new, as compared with those present in normal sea water indicate that 

 " the sulphate ion present in the sea water, from which the majority of the 

 salts were doubtless directly or indirectly derived, has been replaced by the 

 carbonate ion, the proportion of calcium has been somewhat reduced, that of the 

 potash somewhat increased, whilst the proportions of magnesium and of sodium 

 have been increased at rates of nearly 20 per cent, the additions, probably de- 

 rived from the land, being in the form of carbonates." 



Taking the weight of an acre-foot of the soil just below the water table as 

 4,278,.3G0 lbs., with a water content of 42.8 per cent, estimates are made of the 

 amounts of various solid constituents in the water of an acre-foot of soil. 

 These show that " the soil waters in the fertile parts to a depth of 12 ft. from 

 the surface contain in one acre about 43 tons of sodium chlorid (common salt), 

 3§ tons of magnesium carbonate, 3* tons of magnesium sulphate, 2 tons of 

 magnesium chlorid, 1 ton of potassiimi chlorid, 4 cwt. of sodium carbonate, and 

 nearly 3 tons of calcium carbonate. 



" On the nonproductive section the quantities of sodium chlorid and potassium 

 chlorid are simi\ar in amount to those on the fertile parts, but the total mag- 

 nesium salts, which are a little less than in the fertile land — 9 tons as com- 

 pared with 9.3 tons— contain, in round figures, (> tons of magnesium carbonate 

 in place of 31 tons, whilst only about half as much (1| tons) of calcium 

 carbonate is present in it as there is in the fertile land." 



In experiments in which (1) soil water was allowed to evaporate into the 

 air and (2) caused to evaporate into an atmosphere consisting almost entirely 

 of dry carbon dioxid, it was observed that " where the evaporation takes place 

 in air nearly free from carbonic-acid gas, practically the whole of the calcium 

 salts are deposited as calcium carbonate whilst the water is being concentrated 

 to about one-third of its original bulk, and the remaining water becomes a 

 highly saline one containing large proportions of magnesium salts — the chlorid, 

 sulphate, and carbonate — in solution. The calcium salts, which are well 

 known to exercise a profound influence in reducing the highly toxic action of 

 the magnesium chlorid and carbonate on plants, are almost completely re- 

 moved from solution and the soil water becomes in a condition which is poison- 

 ous to vegetation. This is what probably takes place during periods of pro- 

 longed dry weather on more or less wornout sugar-cane soils in which, by in- 

 judicious cultivation and especially by long-continued destruction of the trash 

 by burning, the normal proportions of organic matter have been largely reduced. 

 Where, on the other hand, the evaporation takes place in an atmosphere heavily 

 charged vv^ith carbonic-acid gas as is the air present in soils containing the 

 proportion of organic matter normal to good soils, the lime salts remain in 

 solution until the liquid commences to become a saturated brine and thus for 

 a prolonged period continue to modify the toxic action of the magnesium salts. 

 It is possible on such land that the soil water during drought may become 

 concentrated in the upper layer of the soil without very material injury to 

 the plants until, by concentration of the soil water, the toxic action of the 

 sodium chlorid exerts itself." 



Results of observations on evaporation from sod, 1897-1907, V. Rhip- 

 CHiNSKii {Zliur. Ojnjtn. Agron. (Russ. Jour. Expt. Landtv.), 11 {1910), lS!o. 

 2, pp. 161-177). — Observations on evaporation from sod by means of a special 

 form of apparatus are reported. The apparatus used was a modification of 

 that devised by Rykachev and consisted of a i-eservoir sunk in the soil to its 

 top with an inner box 40 by 25 by 30 cm. in size, into which a piece of sod was 



