132 THE IRRIGATION AGE. 



month later, so that the amount for the year is from 8.4 to 13. 5 inches, 

 or about 33 per cent more, while the mean yield per acre was 23.4 

 bushels in 1879, as against 16.1 bushels in California. There is here 

 in Washington, as in California, a dry period of some 60 days, in 

 which the crop is forced to come to maturity. 



It appears, therefore, from the observations and experiments re- 

 garding the number of inches of water which may be used in produc- 

 ing a ton of dry matter, and from practical experience in arid climates, 

 that on deep, fertile soils, well managed, good paying yields of wheat 

 may be realized where the amount of rain is as small as 7 to 8 inches 

 and large yields when it reaches 12 to 15 inches. 



But like amounts of rainfall are not equally productive and three 

 notable examples may be cited. The first is the San Joaquin Sacra- 

 mento valley, the second in eastern Washington, to which reference 

 has just been made, and the third is a broad belt lying just west of 

 the 97th meridian stretching through the western Dakotas, Nebraska, 

 Kansas and on into western Texas. These areas received very nearly 

 the same amounts of rainfall for the year, but the distribution of it in 

 time is very different. In California the rain all falls in the six months, 

 November to April, inclusive; in Washington it is from October to May, 

 inclusive; while in the 97th meridian region much the larger part of 

 the rain falls during the months between April and September. The 

 eastern region, therefore, has its moisture well distributed through. 

 the growing season, while both of the western areas mature their 

 crops in from 30 to 60 days on continuous nearly rainless weather; and 

 yet, if we compare the yields of barley, oats, ryes and wheat in the 

 three districts taking the Tenth Census figures for California, Wash- 

 ington and Kansas for comparison, the yields are largest in Washing- 

 ton and smallest in Kansas, standing as follows: 



Washington ' California Kansas 



bu. per acre bu. per acre bu. per acre 



Barley.. 36 21 12.5 



Oats 41 26.8 19 



Rye 14 9 12 



Wheat 23 16.1 9-3 



As the soils in the three regions are notably fertile, and were in 

 1879 very close, on the average, to virgin conditions, the differences 

 in yield can hardly be attributed to differences in plant-food other than 

 as influenced by soil moisture; and as the quantity of rain which falls 

 in Kansas during the growing season, April to September, inclusive, 

 is 11.5 to 16.8 inches, while that in Washington is only 8.4 to 13,5 

 inches, it appears plain that in some way the available moisture is 

 more effective on the Pacific border than it is in the 97th meridian 

 region . 



It would be of very great practical importance to understand fully 

 the causes which permit so small an amount of rain as that of eastt m 



