THE IRRIGATION AGE. 233 



drained land is from eight to ten degrees warmer than the same land without drain- 

 age, and the additional warmth makes a very material difference in the growth of the 

 trees and plants. 



Lands irrigated from wells which yield cold water, should have individual stor- 

 age reservoirs, so that the water can be pumped into them and allowed to stand and 

 become warm before going on the land. All growing plants are checked in their 

 growth by the application of cold water. In case a reservoir is impossible, then it 

 would be best to irrigate every other space between the trees, so that only one-half 

 of the roots of a tree would be chilled at one time. In fact, this latter method of 

 irrigation seems to work most successfully, whatever the source of the water supply, 

 and many orchardists believe it to be the only real way to keep up a continuous 

 growth. 



Good land is in such abundance, that land underlaid with hard pan close to the 

 surface should at present be passed by. Young trees may do well on such soil and 

 come to fruiting early, but the trees are short lived and the land requires too fre- 

 quent watering while the fruit is maturing. Test wells determine the depth to the 

 water. 



The necessity for a year or more's weather record is also self-evident. We 

 could then tell by comparison approximately the amount of average temperature^ 

 also the amount of wind: and all these points should be most carefully studied. Had 

 such local tests been made before the attempted development of many of our locali- 

 ties, thousands, yes, millions of dollars spent in experimental planting would have 

 been saved. 



3. What crops can be grown and what will be the average revenue per acre? 

 The first part of this question can be determined by: 



a. The character of the soil, the temperature, the wind, in brief its general 

 local conditions. 



b. A comparison of this data with that of well-established communities. 



The question can then be answered very readily, if the products proposed to be 

 grown are such as have been marketed for a considerable period of time, staple pro- 

 ducts as we call, them, and upon such production only would it be safe to base an 

 estimate. 



Speculative agriculture can form no basis of calculation. How many hogs for 

 sausage, not how many lilies for perfume, must be the ratio; how many people will 

 a given area sustain, not how many roses can be raised. 



4. How much water will be required to produce an average crop? No other 

 question furnished such a variety of answers at the convention at San Francisco as 

 this. The answers were based upon personal observation and whereas one man 

 stated positively that three acre-feet of water was needed in his location, another 

 said that a crop of citrus fruit would follow the application of one-half an acre-foot. 

 In the first case the depth to the surface water was under fifty feet, and in the sec- 

 ond, presumably more than one hundred. Ln general, three things will fairly de- 

 termine the amount of water necessary in the locality. 



a. The character both of top soil and substrata. 



b. The average ratio of evaporation. 



c. The variety of crops to be raised. 



As a rule, the soil that drinks in the moisture most readily parts with it most 

 slowly. Sandy loams retain water longer than adobe soils, especially if not perfect- 



