PRINCIPLES OF MANURING 113 



Rough-stalked Meadow Grass, and Perennial 

 Ryegrass. The herbage, therefore, of the 

 nitrate plots, being deeper rooted, is better 

 able to withstand drought ; and this charac- 

 teristic, combined with the more extensive 

 feeding range of the deep roots, has reacted 

 beneficially on the yield. It may be added, 

 also, that an acid condition of the soil, in- 

 duced by the long-continued use of ammonium 

 salts, has encouraged the increase of Sorrel, 

 and the same cause has markedly repressed 

 the growth of the Leguminosae. 



Other things being equal, sulphate of 

 ammonia is relatively more suitable for 

 application to turnips and potatoes, because 

 in the case of these crops the manure can be 

 thoroughly incorporated with the soil, and, 

 moreover, growth taking place at a time of 

 year when the micro-organisms of the soil 

 are specially active, ammonia is quickly 

 brought into a condition in which the plants 

 can utilize its nitrogen. But although sul- 

 phate of ammonia appears to be relatively 

 well adapted for use on root crops generally, 

 notable exception is furnished by the man- 

 gold crop, which at Rothamsted has re- 

 sponded in a very marked manner to the 

 use of nitrate of soda as contrasted with 

 sulphate of ammonia. The causes of the 



