S88 WEEDS : GENERAL 



are prominent members. Such weeds, by their pecuUar anatomy 

 and physiological powers, are adapted to live in acid and water- 

 logged soils with poor aeration and abundant supply of water. A 

 removal of the latter conditions makes the ground unfit for their 

 growth. All British cultivated farm plants require thoroughly 

 aerated soil and an absence of stagnant water for their satisfac- 

 tory cultivation ; draining of wet arable land makes a vast im- 

 provement in the yield of the crops to be obtained from it, and 

 exterminates many troublesome weeds such as those mentioned 

 above. 



The draining of marshy pastures and damp meadows removes 

 from them many weeds which cannot practically be annihilated 

 in any other way. 



(/) The application of manures and various other substances 

 to the ground makes a difference in the vegetation of a field. 



Nitrate of soda, for example, stimulates leafy growth of the 

 grasses, and the latter then choke out many plants which are not 

 so much influenced by it. A dressing of lime often improves 

 the growth of the leguminous portion of the flora of a meadow 

 or pasture, and checks many useless plants. Many mineral 

 manures are employed to reduce weeds ; those acting most 

 beneficially for the purpose are common salt, lime, gypsum, 

 superphosphate of lime and basic slag. 



It is almost impossible to apply any substance to the surface of 

 grass land without making some alteration in the component 

 vegetation, and it is important that careful observations should 

 be made upon this subject by farmers. 



Ex. 273. — Separate plots of old pasture land, about A of an acre in area 

 should be manured with 3 cwt. nitrate of soda, 6 cwt. superphosphate of lime, 

 10 cwt. basic slag, and I ton of lime per acre respectively, and the effect upon 

 the nature of the herbage noted. Comparison to be made with a similar plot 

 untreated. 



Note the prevalence of coarse or fine grasses, clover, and other plants. 



