THE IKRIGATION AGE. 



81 



tremendous difference within such narrow limits seems 

 unreasonable. 



If, however, moisture stored in the soil above the 

 limit to which wheat can exhaust soil, be taken into 

 consideration, the value per inch of the first 2.5 inches 

 of irrigation, plus the soil moisture, was a little less 

 than three bushels, while the corresponding inch value 

 when five more inches of irrigation water were added, 

 was about 2.3 bushels. Such a gradual decrease is, of 

 course, more reasonable. 



As more irrigation water is added, the bushel yield 

 per inch steadily decreases, thus showing that, inch 

 for inch, the water stored in the soil in the spring is 

 of higher crop producing value than any irrigation 

 water applied. Certainly, in considering the effect of 

 any depth of irrigation upon crop production, the 



optimum amonsit in this paper, but simply to call 

 attention to the fact that in the case of all annual 

 crops, the supply of moisture must be most available 

 from early youth to the time of flowering. Especially 

 does the demand rise just before and during early 

 flowering time. When the flowers are once well pro- 

 duced, the crop needs much less water for its life proc- 

 esses, and then the soil moisture may be allowed to 

 fall. If this be so, we have another argument in favor 

 of the largest possible amount of capillary water in 

 the soil in early spring. Thus, also, the supplementary 

 nature of irrigation is emphasized. 



CONCLUSION. 



The limits of this paper do not permit the develop- 

 ment of this subject. The barest notice must suffice 



An Irrigation Scene on Union Pacific Railway In the South Platte Valley. 



amount of moisture in the soil must always be taken 

 into consideration. 



ANOTHER VALUE OF EARLY SOIL MOISTURE. 



Plants do not possess the power of regulating the 

 amount of moisture that may be taken from the soil. 

 From a moist soil much more water is taken per day or 

 week than from a drier soil. If the soil is kept very 

 dry, much of the energy of the plant is lost in over- 

 coming the attraction between the soil particles and the 

 thin water film. If the soil is kept very moist, much 

 of the energy is consumed in evaporating immense 

 quantities of water into the air. In either of the 

 above cases, the lost energy means a reduction in the 

 yield of dry matter per acre. It should be the aim of 

 the wise irrigator to keep the soil supplied with the 

 best amount of water at all times, that is, the propor- 

 tion of soil moisture that will furnish the amount 

 necessary for thrifty plant growth in the most econom- 

 ical manner. It is not the purpose to discuss this 



at this time. All plants are like wheat in the manner 

 in which they appreciate the start given them by an 

 abundance of moisture, stored in the soil in early 

 spring. When it shall be understood by irrigator and 

 canal manager, that over a large portion of the irri- 

 gated area, irrigation should be supplemental to 

 the natural precipitation, very little irrigation will 

 be given wheat and the other grains, and correspond- 

 ingly less water will be given sugar beets, potatoes 

 and other longer growing crops. As a consequence, 

 the water at the disposal of the farmer, will he made 

 to cover more acres; more crops will be obtained per 

 acre inch of water, and the wealth of the irrigated area 

 will be increased. 



We are yet in the beginning of irrigation knowl- 

 edge. There is a vast undiscovered field covering the 

 relation of crops and soils to water under the climatic 

 conditions of the Western United States. The sup- 

 plemental value of irrigation will not be the least 

 important branch of that coming study. 



