1588 



OPENING UP LAND FOR CULTIVATION 



OPENING UP 



LAND FOR 

 CULTIVATION 



under suitable conditions, the reactions causing soil acidity proceed ac- 

 cording to chemical laws. The acidity in well aerated soils, in particular 

 in cultivated upland soils, is due to the hydrolysis of silicates, of which 

 the bases are removed by plants and by soil water, and to the silica and 

 acid silicates left behind. The weathering process in soils can be repro- 

 duced by treating powdered basalt, granite felspar, etc., with carbonated 

 water and filtering : the residues are acid to litmus. In dry regions the 

 soluble salts acciimulate and cause alkalinity. In these soils organic 

 acids derived from plant residues are of little importance : they may be 

 formed, but are quickty transformed. In badly aerated soils e. g.in peat 

 soils, the plant remains are decomposed much more slowly ; instead of 

 being oxidised to carbon dioxide, much of the carbon remains in the soil 

 in organic combination as the so-called humus acids, and eventually is 

 transformed into coal. 



The latent acidity of a soil may be largely due to kaolinite and si- 

 milar compounds, or to free quartz; and the results of the determinations 

 of active and latent acidity show that the amounts of different hydroxides 

 that react with the insoluble acids, are approximately chemically 

 equivalent. The fact that acid soils do not take up equivalent amounts 

 of different bases from salt solutions possessing a common ion, is not 

 opposed to the hypothesis that soil acidity is due to the presence of free 

 acids, for the reactions involved would be much influenced by secondary 

 reactions. Bj'' using small quantities of finely powdered soil and large 

 volumes of salt solutions, and minimising the time of contact, the effect 

 of such side reactions can be practically annulled ; and determinations 

 of soil acidity under these conditions give results which are best explained 

 on the assumption of the existence of free acids. Further, the adsorp- 

 tion hypothesis would lead to the conclusion that the acidity of a soil 

 would increase if the particles were ground to an impalpable powder : 

 experiments showed a slight decrease. 



1 164 - The Reclamation of Arid Steppe Soil and of Shifting Sands in the Province of 



Astrakan, Russia. — Vysotzkif G., The flora of Ergenia and the conditions under which 

 it is developed. Tpydu B)opo no npUKMiduou EomanuKl'b {Bulletin of Applied Botany). 

 Year VIII, Nos. lo-ii, pp. 1113-1418. Petrograd, October-November 1915.- — II. Firstov 

 J. G., The shifting sands of the province of Astrakan. CejlbCKoe Xo3HUcmeo u Jlnco- 

 eodcmeo (Agriculture and Sylviculture), Vol. CCV. pp. 616-630. Petrograd, April igi6. 

 Geographical conditions. — In Russia there are three distinct regions 

 of arid steppes : 



i) The Pontic region around the northern margin of the Black 

 Sea. 



2) The Transdon region and that of the northern Caucasus which 

 together form a triangle with apices at Novotcherkassk, Tzarytzin and 

 Mozdok. 



3) The Transvolga region also in the form of a triangle with api- 

 ces at Kamichin, Saratov and Uralsk. 



The last two regions are situated on the edge of a vast semi-desert 

 area which surrounds the Caspian Sea and occupies the greater part of 



