Care of the Growing Crop 165 



practice of doubtful advantage. In most cases, practically 

 all of the weeds can be killed by driving along the row. 

 The weeder is a tool for prevention of weeds rather than 

 their cure. It will not kill those which have got much of a 

 start above the soil or those with underground rootstocks 

 like quack-grass. 



A comparison of potato-growing of 1916 with that of 50 to 

 75 years ago shows how great has been the substitution of 

 tools operated by the power of animals for those worked by 

 man. Where formerly the plow and harrow were nearly 

 the only tools not worked by hand labor, the farmer may 

 now use the horse-drawn planter, fertilizer-sower, manure- 

 spreader, numerous types of cultivators, weeders, ridgers 

 and other tillage tools, the sprayer and the different types 

 of diggers. 



Within the last twenty years the gasoline engine has 

 been developed to a wonderful degree. Millions have been 

 built for automobiles and probably millions more have 

 been sold for farm use, for threshing, feed grinding, pump- 

 ing water and other uses. Gasoline tractors are being 

 rapidly developed to draw farm tools in the field. As yet 

 they have been little used in potato-growing except for 

 plowing and harrowing. A great obstacle to the use of 

 present tractors between potato rows is the width of a track, 

 usually four or five feet. Potato rows are usually about 

 three feet apart and tools for work between the rows must 

 have a tread of about three feet, or else have a six-foot 

 tread, like most potato sprayers. Four-wheeled tractors 

 used to draw tools need two operators, one for the tractor 

 and another to handle the tools. On any but perfectly 

 level land the side movements of front or rear wheels in 

 skidding quickly injure the potato plant. New types of 

 tractors are being developed by which the same two wheels 



