276 THE EFFECT OF MANURES. 



tivation occasions instant war. A grass likes the best that can 

 be got. It will swallow soda, but not when it can get potash. 



"On general principles, all manures tend to drive out the 

 weeds by increasing the better herbage." 



This is certainly very satisfactory, but not true in every par- 

 ticular. 



Mineral Manures Alone. The leguminous plants were largely 

 increased at the expense of the grasses and weeds. The grasses 

 proper scarcely increased at all, whilst the whole plat was thickly 

 covered with perennial red clover and some other leguminous, 

 plants. 



Very different was the action of ammoniacal salts which caused 

 the exclusive increase of the grasses proper, there being scarcely 

 a leguminous plant to be found upon the plot. 



Siqierphosphate of lime, when used alone, slightly increased 

 the grasses and miscellaneous plants, diminishing the legumin- 

 ous. It proved to be of little or no use. 



Ammonia salts alone but slighty increased the crop. The crop 

 was moderate and but little better than the plot unmanured. 



Farmyard manure gave a considerable increase of chiefly gram- 

 inaceous hay and some few weeds, such as Rumex and Achillea, 

 Ranunculus, Carum, attributed chiefly to its mineral and nitro- 

 genous constituents. 



The general result is, that leguminous plants in the meadow 

 were much increased in growth and assimilated more nitrogen 

 from unaided sources over a given area, when they were liberally 

 supplied with certain mixed or primarily soil constituents. 



Farmyard manure greatly encouraged the growth of the good 

 grass Poa trivialis and the bad one Bromus mollis, and when in 

 conjunction with ammonia salts the Dactylis glomerata, under 

 both conditions, Festuca duriuscula and F. pratensis were nearly 

 excluded, and Avenaflavescens, A. pubescens, Agrostis vulgaris, 



