SOIL PHYSICS, CHEMISTRY AND MICROBIOLOGY I74I 



changes take place in the chemical constitution of a soil when it is moved 

 from an arid to a humid climate or vice versa. In general, bacterial acti- 

 vities are far more pronounced under humid than under arid conditions ex- 

 cept with regard to cellulose decomposition. This is probably due to the 

 decrease in the carbon of soils under arid conditions and to the decrease 

 in the water soluble substances. 



1257 - The Relationship between the Osmotic Pressure of the Soil Solution and the 

 Growth ofWheat. — TyjiAiiKOBb M. H. (ToulaikowM. N.) in JKijpHaAo Onumuou 

 AipoHOMiu a.WMti n. C. KoccoBiiiA (Review of Ai^ricultural Experiments dedicated 

 to the memory of P. S. KosSovitch). VoL XVII, No. 2, pp. 123-163. Petrograd, 1916. 

 In order to determine the correlation between the salt content of the 

 soil and the growth of plants, a series of experiments were undertaken at 

 the Station of Besentchouk whore the alkali soils of the Province of Sa- 

 mara are under special investigation. The osmotic pressure of the soil 

 solution was artificialh' raised by the addition of mineral salts to the 

 soil and was studied in its relationship to the growth of Bielotourka 

 wheat, a hard spring variety which is wideh' distributed in the region. 

 The experiments were begun in iQioand a first report has already been 

 jmblished (i). Plants were grown in zinc c^dinders each of which con- 

 tained 5 kgs. of black soil (Tchermozem) and about 50 gms. of a 

 mixture of nutrient salts. Before being filled into the pots the soil was 

 dried in the sun till its moisture content had been reduced to to ton 

 per cent. The nutrient salts were added in the form of solution, l)ut the 

 salts used to raise the osmotic jtressure of the soil sokition {i. e. sodium 

 chloride, nitrate and sulphate; ammonium chloride and salphate; calcium 

 chloride) were applied in the solid form and in three different ways; 



i) The whole amount was mixed with the soil at the start so that 

 the soil solution was immediateh- brought \\\) to the required osmotic 

 pressure. 



2) The salts were added at the rate of one sixth of the total amount 

 per week for 6 weeks. By this means it was possible to reproduce the natural 

 conditions prevailing in alkali soils where the osmotic pressure of the so- 

 lution increases as the growing season advances owing to the decrease of 

 the water content in the soil. By spreading the applications over 6 weeks, 

 the ]dants had received the whole amount before flowering. 



j) The whole amount was added in a single dressing at the time of 

 flowering. 



Distilled water was used for bringing the moisture content of the soil 

 up to 5o per cent of its maximum water holding capacity or in other words 

 to 24 per cent of the dry soil. Selected seeds or pure lines of Bielotourka 

 wheat were employed and careful records were kept of the dates of 

 germination, tillering, shooting, flowering, and ripening. The height of 

 the plants was also measured at different times. When the plants were 

 harvested, the dried grain and straw were weighed separately and the 

 grain was analysed for total and protein nitrogen and for moisture; the 



(i) vSee A'. 191 1, No. 987. {Ed.) 



