REMEDIAL MEASURES 41 



older plants of Penny Cress were dead." Although 

 some of the leaf tips of the wheat were slightly burned, 

 " the yield of grain was considerably larger than from 

 an equal unsprayed area." The question of destroying 

 weeds by spraying is more fully discussed at p. 43. 



Ploughing weeds under is usually satisfactory where 

 weeds are getting the upper hand, especially where 

 annuals are concerned, but this should be before seeding 

 takes place. In garden cultivation weeds may be deeply 

 buried when trenching is done ; even Couch, Bindweed, 

 and Creeping Thistle may be dealt with in this way, as 

 we have proved, but the work must be well done. It 

 has been suggested that Couch might well be piled in 

 large heaps and rotted for manure (see p. 3). 



Use of Tarred Paper. A plan much recommended in 

 the United States for eradicating patches of perennial 

 weeds, like Creeping Thistle and Stinging Nettle, is to 

 cover the whole surface with large sheets of strong 

 tarred paper in order to exclude light. The paper may 

 be pegged down and have a few stones placed on the 

 top. This method is stated to be of great value and 

 very effective. 



" Lawn sands," the basis of which appears generally 

 to be sand and sulphate of ammonia, are largely used 

 for the improvement of lawns, the finer grasses being 

 encouraged, and the weeds suppressed or choked out. 

 Such treatment occasionally has an almost marvellous 

 effect. 



Manuring is a valuable aid in the war against weeds, 

 land in high condition enabling the crop to hold its 

 own. Grass land is rapidly improved by the use of 

 manures (see Chap. V.), and liming is frequently of 

 great value, especially in combating Sheep's Sorrel, 

 Corn Marigold, Spurrey, and some other weeds. 



It was shown many years ago by Heinrich's experi- 



