166 The Rothamsted Grass Experiments. 



nitrogen, than in the amount of total growth that is, 

 produce of hay by doubling the application. In other 

 words, the percentage of nitrogen in the produce was very 

 much increased ; it was, indeed, abnormally high, and 

 indicates a deficient assimilation of other constituents in 

 proportion to the nitrogen taken up. 



An examination of the herbage shows that, with the com- 

 bination of mineral manures and ammonia-salts, the greater 

 the quantity of the latter the more nearly does the produce 

 become exclusively gramineous, and the more does it consist 

 of a few of the most freely growing grasses (Dactylis gloni- 

 erata, Alopecurus pratensis, Agrostis vulgaris, Holcus lanatus, 

 Avena elatior). These, too, take possession of the ground 

 very much in tufts or patches, and grow coarse, strong seed- 

 stems, and broad, flaggy, dark-green leaves. The herbage is, 

 in fact, very coarse, often laid, and dead at the bottom before 

 it is ripe ; indeed, it generally matures irregularly and 

 imperfectly, yielding hay of low quality, though, if the grass 

 were fed off young, or cut green for feeding, it would probably 

 be fairly good food. 



The ash analyses reveal some striking differences in the 

 mineral composition of the produce. There is a markedly 

 lower percentage of lime, a lower percentage of magnesia, 

 and, notwithstanding the produce is so prominently grami- 

 neous, a lower percentage of silica, in the dry substance of 

 the hay, than where the growth is less forced, and the 

 herbage is at the same time more mixed. Of phosphoric 

 acid, and especially of potash, there is, on the other hand, a 

 considerably higher percentage in the dry substance of these 

 coarse gramineous crops, as also there is of chlorine. The 

 percentage, in the dry substance, of lime, magnesia, soda^ 

 sulphuric acid, and silica, has decreased over the later 

 compared with the earlier years, whilst that of the potash 

 and phosphoric acid (and also that of the chlorine) has 

 increased over the later years. The percentage of lime 

 especially has decreased the more, but that of the soda, 



