100 FIELD AND LABORATORY STUDIES OF CROPS 



plants grow only serves the purpose of scattering them, 

 unless that cultivation is persistent enough to keep down 

 all growth of foUage. Salt, coal oil, and sulphuric acid 

 may also be applied, but these are expensive, and per- 

 sistent cutting will usually be found to be the cheapest 

 and most effective method. 



(3) Some weeds indicate poor soil conditions, and the 

 remedy is to improve these conditions. For example, the 

 presence of horse sorrel indicates an acid condition of the 

 soil. An application of lime will improve the soil and cause 

 this weed to be crowded out by more desirable plants. 

 No amount of cutting or cultivating will eradicate it so 

 thoroughly. Wet spots are usually covered with swamp 

 grass and sedges. No amount of cutting will destroy them, 

 but tile drainage will cause them to disappear. 



