i6o 



Bulletin 130. 



every ton of dry matter of potatoes produced there is required 

 422.7 tons of water. In the case of the average yield for 1896 

 with seven tillings when there was produced 343 bushels per 

 acre, the amount of dry matter was 4,342.38 pounds, or 2.17 tons. 

 To mature this amount would require some 917.25 tons of water. 

 This was secured to the plants by early and deep plowing of the 

 land to establish the earth mulch and to prevent loss of the spring 

 rains, and then by frequent surface tillage the mulch was renewed 

 to lessen the loss of moisture by evaporation. 



The conservation of moisture by frequent tillage cannot be 

 too strongly enforced. The liberal application of fertilizers, or 

 the presence of large amounts of readily available plant-food 



55. — Cultivator well suited to potato culture during earlier period of growth. 



will prove of but little value if the moisture supply is 

 deficient. The old notion that tillage must cease as soon 

 as the potatoes blossom, is wrong. It should be continued 

 as late in the season as the growth of the vines will psrmit. 

 As the tops spread out and begin to cover the space between the 

 rows, they partially shade the soil and thus lessen the loss of 

 moisture by evaporation. The cultivator should be narrowed 

 and the middle of the open space kept covered with a loose earth 

 mulch (Fig. 34). The implement best adapted to this work is 

 one having many smill teeth so that it will leave the soil com- 

 paratively level. (See Frontispiece.) Fig. 35 shows an imple- 



