SOIL CONDITIONS AND PLANT GROWTH 



coefficient is found to vary from year to year with the external 

 meteorological conditions, being greatest in dry years and 

 lowest in wet years ; it is also higher in wet soils than in dry 

 ones. Toulaikoff considers that it is these conditions, rather 

 than the biological character of the plant, that determines the 

 magnitude of the coefficient (284). 

 Some of his results are : 



The year 1911 was excessively dry, 1913 was very rainy: 

 1912 was an average year and 1914 was rather dry. 



The effect of variations in water and food supply on the 

 water requirements of plants was studied by Hellriegel, and 

 subsequently by von Seelhorst at Gottingen (256-258), who 

 has worked extensively at the various water relationships of 

 plants. His results with oats are given in Table X. 



TABLE X. EFFECT OF VARYING WATER SUPPLY * AND FOOD SUPPLY ON THE 

 WATER REQUIREMENTS OF OATS. VON SEELHORST (257*1). 



1 The variations in water supply were : 



Where 100 = saturation of the soil. 



