394 



THE SMALL GRAINS 



such cases several causes have been assigned. Sometimes 

 it is said to be due to too much available plant-food, caus- 

 ing an overgrowth of the plant above ground compared 

 with the roots. The roots are thereby not able to furnish 

 moisture to the plant in a dry period as rapidly as it is 

 evaporated, and the plant dries out or burns, and the 

 spikes fail to fill. As a partial proof of this cause, it is 

 stated that winter cereals are not so affected, as they have 

 larger root systems. However, winter cereals are so nearly 

 mature before the hottest weather begins, that usually 

 they cannot be injured. If crop burning is due to an over 

 supply of plant-food, either summer fallowing should be 

 done every third year or some cultivated crop should re- 

 place the fallow (Thorn and Holtz, 1914, pp. 25-27). 



The following tabular statement will be of interest in 

 this connection, showing the excess of nitrate foods that 

 are formed in the soil under summer fallow. The inves- 

 tigations were made at the Longerenong Agricultural 

 College in Victoria, and are given by Richardson (1912-13). 



TABLE X. FORMATION OP NITRATES IN FALLOWED AND 

 NON-FALLOWED LAND AT LONGERENONG AGRICULTURAL 

 COLLEGE (VICTORIA), 1911-12. THE FIGURES ARE NITRATE 

 NITROGEN IN PARTS TO THE MILLION OF THE SOIL. 



