MANURING AND FERTILIZING 49 



Wisconsin, shows that if it is assumed that under the 

 existing climatic conditions of that State 18 inches of 

 rainfall during the growing season is sufficient for po- 

 tatoes, then, on this basis, there was a shortage of 4 

 inches or more in ten of the past twenty-one years. In 

 Utah ' it was noted that the largest yield was obtained 

 from a plat irrigated every eighth day and receiving 14 

 inches of water, and another year* 16.62 inches of water 

 withpradlicall)' no rain produced a yield of 423 bushels 

 per acre. The importance of water was also shown at 

 the same station/ when amounts of water var>'ing be- 

 tween 4.3 inches and 9.45 inches were applied between 

 July 18 and August 6, and the yield increased with 

 the increase in amount of water. At the New Jersey 

 Station* irrigation increased the yield 36.4 per cent., 

 while at Wisconsin the increase has been 159.58 ^ bush- 

 els per acre over the unirrigated plat, and the average 

 gain per year during the six years — 1896-1901 — was 

 83.9 bushels per acre. That some risk must be taken 

 in irrigating heavy soils in a humid climate was 

 demonstrated at Wisconsin.* Thus, in one year, 

 while there was an increase of 81.4 bushels per acre 

 from irrigating sandy land, on heavier land the yield 

 was reduced 56 bushels per acre because heavy rain 

 followed the second irrigation. 



Corn and potatoes require somewhat similar amounts 

 of water to make one pound of dry matter. The figures 

 of Wilfarth and Wimmer ' and Whitson* are as follows: 



1 Utah Report, 1893, p. 180. " Utah Bui. 26, p. 14. 



» Utah Bui. 5. * N. J. Report, 1900, p. 184. 



* Wis. Report, 1901, p. 198. • Wis. Report, 1900, p. 1S8. 



* E. S. R., XIV., p. 561. * Wis. Report, 1902, p. 191. 



