160 The Rothamsted Grass Experiments. 



The result is, over the twenty years, considerably more 

 than twice as much hay as without manure, nearly twice as 

 much as by the same amount of ammonia-salts used alone, 

 and nearly once and a half as much as by the same mineral 

 manure used alone. During the second period, however, 

 there was a falling off, as compared with the first, of nearly 

 10 per cent. 



The average annual yield of nitrogen per acre was more 

 than twice as much as without manure, more than once and 

 a third as much as by the same amount of ammonia-salts 

 alone, and nearly once and one-third as much as by the same 

 mineral manures used alone. There was a decrease in the 

 yield over the second ten years as compared with the first. 



Of total mineral constituents about two and one-third 

 times as much were taken up as either without manure, 

 or with the ammonia-salts alone, and about once and a third 

 as much as when the same mineral manure was used without 

 ammonia-salts. There was a falling off of 18 per cent, in 

 the second period as compared with the first. 



[n discussing the character of the herbage, it is necessary 

 to bear in mind the corresponding results obtained (a) without 

 manure, (&) with mixed mineral manure, (c) with ammonia- 

 salts alone. On the plot now under notice, the mixture of 

 nitrogenous and mineral manures gave rise to herbage still 

 more gramineous than that produced by the ammonia-salts 

 alone; in fact, the weight per acre of gramineous herbage 

 averaged more than twice as much ; the proportion of the 

 produce due to both leguminous and miscellaneous species 

 was also less, though the average weight per acre of both 

 was rather more. But the botanical composition of the 

 gramineous herbage was more varied. Thus, whilst Festuca 

 ovina and Agrostis vulgaris contributed by far the larger 

 proportion of the total herbage grown by ammonia-salts 

 alone, and Anthoxanthum odoraturn (sweet vernal), Holcus 

 lanatus (Yorkshire fog), and Dactylis glomerata (cocksfoot) 

 were only very moderately, and every other grass sparingly 



