1084 SOIL PHYSICS, CHEMISTRY AND MICROBIOLOGY 



tural phosphates is difficult to utilise in basic soils ; the use of fertilisers 

 of this kind must therefore be carefully avoided in soils shown by microbio- 

 logical analysis (i. e. with Azotobacter) to be basic. On the contrary, there 

 cannot be any relation between the reaction and basic quality of the soil on 

 the one hand and the utilisation of superphosphates and basic slag on 

 the other, nor yet between the property of assimilating phosphates difficult 

 of solution and the capacity of setting free acids, as for instance acetic 

 acid from calcium acetate (i). 



XIV. — ■ Influence exercised by the Nature of Earths on the Bacteria and 

 Chemical Condition of the Soil (2). 



84 ] - Conversion of Soluble Phosphoric Acid into Insoluble Phosphoric Acid in the Soil 

 under the Influence of Physical, Chemical and Biological Factors. — SkalkijS., in 



lO.M-cHo-pjicch'an C('.ihrh(>-xn-_if/i(cm6i-HHnfi ro.ifWd (Agricultural Gazette of 

 Southern Russia), XVIIth Year, Nos. 33, 34, 36, 37 and 38, pp. 6-7; 6-7; 7-8; g-ii ; 

 and 6-8. Kharkov, 1915. 



The experiments were carried out at the agricultural experiment Sta- 

 tion of Ploty (Podolia), where, for several years running, both by chemical 

 analysis of the soil and experiments condticted in the laboratorj'' and the 

 open field, it was ascertained that among the principal elements of ferti- 

 lity in the soil of the vStation, classed as " tchernoziom ", the most deficient 

 was phosphoric acid, that is, in a form which could be readily assimilated 

 b}^ plants (3). 



The object of the experiments was to study the intensity of fixation 

 of phosphoric acid soluble in water, added to the soil, under the influence of 

 chemical, physical and biological factors, in variotis layers of soils under a 

 different cultural condition. By biological factors is meant the action of 

 the micro-organisms of the soil and that of plants. In the experiments un- 

 dertaken, plants were excluded. Consequently only the fixation of phos- 

 phorus by micro-organisms was studied. 



The experiments were conducted with 4 different soils : April fallow 

 soil, i. e. that begun to be tilled in April ; soil which had been uncultivated 

 for many years ; kitchen-garden soil ; and finally the soil of an old oak wood. 

 Two layers were studied in each of these lands, the one arable o to 17.7 

 cm. deep, and the other below the first, from 17.7 to 35.5 cm. deep. For each 

 experiment a quantity of earth corresponding to i kilogram in absolutely 

 dry condition was taken. The experiments are divided into 2 series : in 



(i) Tidsskrift for Landbriigets Planteavl, VoL XX, pp. 90-104. Copenhagen, 1913. — Fiih- 

 liiig's landwirtschaftliche Zeitiing, Year LXII, pp. 392-405. Stuttgart, 1913. 



(2) See B. June 1915. No. 682. (Ed.) 



(3) In the publication of the Department of Agriculture « Ce.TibfKO-xonHiicTBOUHun, 

 ii})OMHfeJl'i> BT. Pocciii » (Agricultural Industry' in Russia), (1893-1913), Petrograd, 1914, 

 published in Russian and I'rench, it is stated, in connection with the Ploty Station (in the 

 chapter where brief particulars of the scientific work of the principal Russian Agricultural 

 Kxperiment Stations arc given), that " its investigations in connection with the conditions 

 affecting the contents of the soil in two principal elements of fertility, nitrr)gen and phos- 

 phorus, have gained it a wide reputation ". The results of the experiments summed up in 

 this article supplement thoNO which appeared on page 188 of the publication in (lueslion. 



