CEREALS UNDER IRRIGATION 429 



463. Increasing the duty of water. In the experi- 

 ments at Gooding, Idaho, described above, the acre-yields 

 of spring wheat in the duty of water tests ran from 15.87 

 bushels to 26.08 bushels, while those of the time irrigation 

 experiments with the same cereal ranged from 29.22 bushels 

 to 50.12 bushels, with no difference in conditions what- 

 ever, except that the former experiments were on raw sage- 

 brush soil and the latter on old alfalfa ground. The 

 yields on alfalfa ground were almost twice those on new 

 land. One lesson learned from the 2 series of experi- 

 ments compared, therefore, is that increasing the soil 

 fertility also increases the duty of water. The applica- 

 tion of stable manure would, without question, have a 

 similar effect. There is not only an immediate gain in crop 

 returns following the alfalfa of nearly 100 per cent, but the 

 soil is put into a condition permitting economy in the use 

 of water probably for some time afterward, a fact of the 

 greatest importance, considering the future scarcity of 

 irrigation water that will certainly occur. 



464. Making the most of the precipitation. Another 

 fact of importance in connection with economy in the use 

 of water is that after all, even in the driest districts, the 

 natural precipitation produces a large percentage of the 

 dry matter of the irrigated crop, often the larger propor- 

 tion. Much of the water commonly applied in irrigation 

 is never used and may be actually harmful. Unless the 

 rainfall is exceedingly light there is always sufficient, if 

 well conserved, to make a considerable crop. It was the 

 study of these questions of the quantity of water required 

 for a crop and what can be expected from the rainfall 

 alone, with proper soil management, that had much to 

 do with the development of dry-farming. In determin- 

 ing the dry matter to an acre of different crops produced 



