rimicATioN kxi'kimmknts in idaiio. 



35 



the months of Juno and July. Many instances have come to the 

 attention of the writer where the advocates of a high duty have over- 

 looked the unequal requirements of the different months of the season, 

 and it is desired to emphasize the fact that this must not be ignored 

 if the best use of the water is to be secured. 



Table XVIII gives a general summary of the results that have been 

 obtained upon porous, sandy, and gravelly soils. This table has 

 been constructed by averaging the requirements -of grain and alfalfa 

 on these soils during the first two years of the investigation in the 

 same manner used with the clay soils, there not having been a sufficient 

 number of tracts of this type of soil experimented upon during the 

 last two years of the investigation to be included in such a summary 

 table. 



Tablk XVIII. — Average depths of water applied to 21 selected fields of grain and alfalfa 

 on porous, sandy, and gravelly soils. 



[Altitudes ranging from 2,G00 to 5,800 feet.] 





Season. 



Num- 

 ber of 

 plots. 



Depth of water applied. 





Crop. 



April — 



May. 



June. 



July. 



Au- 

 gust. 



September— 



Total 



for 

 season. 





1-15 



10-30 



1-15 



10-30 





Alfalfa 



1910 ' 

 1910 

 1911 

 1911 



7 



10 

 6 



8 



Feet. 



Feet. 

 0.53 



Feet. 



1.12 

 .03 

 .92 



Feet. 

 1.69 

 1.44 

 1.84 

 .90 



Feet. 

 1.96 

 .66 

 1.12 

 1.06 



Feet. 

 1.13 



.30 



2.27 



.94 



Feet. 



Feet. 



Feet. 

 6.43 









2.49 



Alfalfa .- 



.18 



0.20 





6.58 





2.90 



















.18 

 3.9 



.52 

 11.3 



1.47 

 32.0 



1.20 

 26.0 



1.18 

 25.6 



.06 



1.3 





4.60 













1 









Table XVIII shows that porous soils require a larger supply of 

 water for their efficient irrigation than the medium soils, the exact 

 quantity required being governed by the porosity of the soil, the 

 method of preparation, and the skill used in the application of the 

 water. The results shown in this table indicate that an application of 

 4.6 feet to the acre per annum will be required for this type of soil, 

 of which 3.9 per cent will be required during the last half of April; 

 11.3 per cent during the month of May; 30 per cent during June; 26 

 per cent during July; 25.6 per cent during August; and 1.3 per cent 

 during the first half of September. 



SURFACE WASTE. 



The measurements just given do not include waste from irrigated 

 lands. In the variation experiments the waste from the various 

 plots was measured, with the results shown in Table XIX. 



