240 



SOILS. 



as actually observed in the work of the Irrigation Division of 

 the U. S. Dep't of Agriculture, under the direct supervision 

 of Prof. R. H. Loughridge of the California Station. The 

 mode of percolation is shown for two soils, a heavy loam and 

 a sandy one, both in the vicinity of Riverside, Cal. 



The upper section shows the variation in penetration in one 

 and the same soil with the same kind of furrow, the broken 

 line indicating the cessation of the flow in the furrows; after 

 which there was a still farther penetration of the water to from 

 6 to 9 inches deeper. 



The second section from above shows the percolation of the 

 water respectively in wide and narrow furrows of the same 

 depth. It is evident at a glance how much more effective is 

 the wide furrow in utilizing the limited time during which the 

 irrigator usually has the flow at his command. 



The third section shows several practically important points 

 in favor of the wide and deep instead of narrow and shallow 

 furrow. It is seen that in doubling the width and depth, the 

 penetration has also nearly doubled. Moreover, it is seen that 

 in the deep furrow the water has not in the course of seven 

 hours reached the surface at all, being still six inches away; so 

 that in view of the diminishing ratio of capillary ascent, it 

 probably would not have reached the edge of the furrow, at 

 the surface, in less than thirty hours. Thus all surface evapo- 

 ration, which oftentimes causes the loss of 50 % of the water 

 entering the shallow furrows, would be prevented ; and a dry 

 furrow-slice might be turned into the furrow immediately after 

 the cessation of the water-flow, effectually obviating the need 

 of subsequent tillage also. The cost of the latter, together 

 with the saving in water, and increased efficiency of the water 

 by deeper penetration, will much more than offset the addi- 

 tional cost and trouble of plowing deeper furrows. 



There is therefore every reason for doing away with the 

 wasteful, easy-going practice of irrigating in numerous shal- 

 low furrows, by which the irrigator loses up to half of the 

 water paid for, by evaporation ; is compelled to wait for the 

 soaked surface to dry before being able to turn back a furrow- 

 slice into the furrows to prevent the drying-out of their mois- 

 ture; and by losing penetration of the water, is obliged to 



