The Effect upon the Crop. 237 



action begins when 10 milligrams of copper oxide are present in 

 1 liter of water, but when only 5 milligrams per liter are present 

 no marked effects can be seen. 



" 2. If solutions of copper sulphate and of copper nitrate are 

 applied to soils, the plant food present, especially lime and 

 potash, are dissolved and washed away; the copper oxide is 

 absorbed by the soil. As a result of these two processes, the 

 fertility of the soil is more or less decreased. 



" 3. Barley and oats suffer more than grass from solutions of 

 copper sulphate and copper nitrate; copper sulphate is more 

 injurious to corn than to beans. 



"4. The injurious action of copper sulphate and copper 

 nitrate is counteracted if an excess of the carbonate of lime is 

 present in the soil. But as soon as this excess has been acted 

 upon, the injurious processes take place in the same manner as 

 in soils in which no lime is found." 



V. UPON THE VALUE OF THE CROP. 



It is scarcely necessary to enter into details regarding the 

 benefits derived from proper applications of insecticides and 

 fungicides. Experiment stations and private growers have 

 many times demonstrated that the market value of the product 

 is increased to such an extent that the cost of materials and of 

 labor is returned many-fold to the grower, whenever proper 

 applications have been made. Indeed, the conditions now are 

 such that it is as necessary to spray certain crops as it is to cul- 

 tivate them. Doubts are no longer entertained concerning the 

 treatment of potatoes with arsenites ; the operation is generally 

 performed as one of the regular duties in obtaining a crop. The 

 majority of the best apple growers have come to feel the same 

 concerning apples. They spray with insecticides for the codlin- 

 moth and other insects, and with the Bordeaux mixture for 

 fungous diseases. The operations have passed the stage of 

 experiment, and are now considered in the light of a necessity. 



The grape is another striking illustration of the same truth. 

 In many sections, especially in the southern states, it is practi- 

 cally impossible to obtain a sound crop on account of the abun- 

 dance of fungous diseases. There it is not only a question of 

 profits, for it is difficult to obtain any crop whatever. Peaches, 



