96 CIVIC BIOLOGY 



tearing off half the roots of the corn plants for centuries, 

 and laboriously reducing the yields from 30 to 50 or more 

 bushels per acre, some one hit upon the idea of studying 

 applying " cultivated thought " to the roots of the single corn 

 plant. It was discovered that many of them spread out near 

 the surface, five, six, or even seven feet in every direction. 

 Next came the thought, May not too deep cultivating injure 

 these roots ? The experiment has now been tried of shaving 

 the weeds without stirring the soil at all, applying careful 



FIG. 48. Two plots of corn on peaty swamp land 



Left, fertilized with phosphorus (not needed) ; crop, 0. Right, fertilized with 



potassium ; crop, 72 hushels per acre. Seed, cost of fertilizer, and lahor on the 



two plots about equal. Photograph hy Cyril G. Hopkins 



shallow tillage to comparable rows in the same fields. Results 

 have shown, on the average, equal yields from the uncultivated 

 rows. Figure out, for your farm, township, county, state, or 

 for the United States, how many dollars' worth of labor this 

 one discovery may save annually. 



Pure-bred selected strains. Again, we have learned that by 

 breeding and selection of productive strains the crop may be 

 increased without additional labor. This fact gives the added 

 value to pure-bred stock in animals and plants. Plalf the plants 

 in an ordinary field of potatoes or corn may be "loafers"; half 

 the trees in an ordinary orchard may be " resters " ; half the 



