164 EXPEEIMENTS UPON GRASS LAND 



Plot 16, which receives the smaller quantity of nitrate of 

 soda, still grows a very large crop, averaging 48 cwt. over the 

 whole period. The vegetation resembles that of Plot 14, but is 

 even more varied, there being about four times as much 

 leguminous herbage, among which the Meadow Yetchling 

 predominates. This plot probably marks the limit of the 

 amount of nitrate of soda which it would be profitable to apply 

 in ordinary farming, since the second 275 lb. per acre of nitrate 

 of soda on Plot 14 has only produced an average increase of 11 

 cwt. of liaj^ 



Reviewing the whole of the evidence, nitrate of soda is 

 distinctly a better manure for hay on the Rothamsted soil 

 than are ammonium-salts, producing more grass and that of 

 a better quality. 



On Plot 10 the potash is omitted from the mineral manm'e, 

 though the other minerals and the nitrogen are the same as on 

 Plot 9. The result of the omission of the potash is a consider- 

 able decline in yield, which has become more accentuated as 

 the experiments have progressed and the original stock of 

 potash in the soil has been reduced. The herbage consists 

 even more wholly of grass than does that of Plot 9, and the 

 development of flower and seed is distinctly later. 



Plot 4-2 receives the same ammonium-salts, supplying 86 

 lb. of nitrogen, and superphosphate only, so that it compares 

 with Plot 9, except for the entire absence of alkaline salts. 

 The lack of potash shows itself in a great reduction of crop, the 

 average over the whole period having been only 35 cwt. against 

 54 cwt. on Plot 9. It is thus much below Plot 10, also with- 

 out potash, but which receives magnesia and soda. The herbage 

 on this plot again consists almost wholly of grasses, which have 

 a very dark green colour and are late to mature. The dwarf- 

 growing and shallow-rooted grasses predominate ; Sheep's 

 Fescue constitutes more than one-half, and Avith Sweet Vernal 

 and Smooth-stalked Meadow Grass, as much as 85 j^er cent, of 

 the whole herbage. 



The characteristic appearance of the herbage is well seen in 



