GROWING BY IRRIGATION. 289 
to the amount of water available. A yield of 6 tons 
per acre actually needs 30 inches of water and cer- 
tainly there will be some loss by evaporation from 
the surface of the soil and by percolation through 
into the subsoil. The Utah Agricultural Experi- 
ment Station in co-operation with the United States 
Department of Agriculture made numerous tests of 
water used, with varying amounts and varying fre- 
queney of application. Briefly, it was learned that 
frequent applications gave much larger returns than 
infrequent, and that the yield was somewhat directly 
in proportion to the amount used. 
RESULTS OF EXPERIMENTS IN IRRIGATING ALFALFA IN UTAH. 
Inches of water Number of Yield per acre, 
applied. irrigations. in tons. 
17.058 3 3.125 
17.33 4 3.468 
24.97 4 5.017 
25.002 2 1.55 
61.465 12 6.243 
Penetration of Roots in Irrigated Soius.—Soils in 
the arid regions are quite unlike those of humid 
regions. There is often little difference in physical 
texture or fertility between the surface soil and sub- 
soil. Furthermore they are usually more permeable 
than soils in humid regions; both water and air can 
enter them readily. Thus alfalfa roots penetrate to 
great depths in such soils. Roots have been traced 
to a depth of 30’ and even farther. And all down 
in that soil will be found air, nodules, bacteria; it 
is a vast factory of nitrogen-gathering, wonderwork- 
ing plant life. No wonder the ‘‘deserts blossom as 
the rose’’ when water is applied to them. 
Grassing the Ditch Banks,—It is a convenience to 
