WORKING THE SOIL 151 



after year. We are using lime to correct the acidity, 

 but the use of lime requires better plowing and better 

 after cultivation to thoroughly mix the trash with the 

 earth to make soil conditions favorable to the different 

 kinds of soil bacteria. Unless we pay special attention 

 to the humus content of the soil we are likely to use 

 lime to dissolve out plant foods that are not needed by 

 the present crop, and, therefore, cannot be utilized. 

 This is what the old adage means which reads : ' i Lime 

 enricheth the father but impoverisheth the son. ' ' When 

 that was written the world had no proper tillage tools 

 and the importance of humus was not even dreamed of. 



Not so many years ago farm plows were made of cast 

 iron. Then came the steel moldboard, which was sup- 

 posed to be the acme of perfection in plow making. 

 Steel would scour and turn the furrow in fluffy soils 

 where cast iron would just ropt along without turning 

 the ground at all. Later the art of molding steel was 

 studied and perfected until many grades and degrees 

 of hardness were produced and the shape of the mold- 

 board passed through a thousand changes. The idea 

 all the time was to make plows that would not only 

 scour but polish in all kinds of soil. At the same time 

 they must turn under all of the vegetable growth to 

 make humus, to kill weeds and to destroy troublesome 

 insects. Besides these requirements the soil must be 

 pulverized and laid loose to admit both air and mois- 

 ture. These experiments gradually led up to our pres- 

 ent high grade plows of hardened steel and what is 

 known as chilled steel. 



Besides the hardness there are different shapes de- 

 signed for different soils so that a plow to work well on 

 one farm may need to be quite different from a plow to 

 do the best work in another neighborhood. The furrow 



