TRRTCATTON EXPERIMENTS IN IDAHO. 



33 



that this tabic may bo used far more than the corresponding one 

 (Table XVIII), which shows the average volumes of water applied to 

 porous soils. As has been stated elsewhere in this report, the irri- 

 gation requirements of any particular crop on any soil are influenced 

 by many factors and will bo found to vary on different farms and 

 during different years, but as this table includes the results of 171 

 selected tracts of this particular type of soil, covering a period of 

 four years, thus effectually neutralizing the individual differences of 



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Fig. 9.— Amounts of water required each month of the irrigation season by an Idaho project devoted 

 to equal areas of grain and hay on medium clay loam or sandy loam soil. 



the seasons, of irrigators, and of the tracts themselves, it is consid- 

 ered that the results will be found to be very dependable 



Keeping in mind that the table shows averages only, and that 

 individual crops, farms, projects, and seasons are bound to depart 

 from the average, the table shows that a project devoted to equal 

 areas of (1) grain, orchards, and general root crops, and (2) hay, 

 including alfalfa, clover, timothy, and pasture, on average southern 

 Idaho soil should furnish sufficient water so that an average of 2 feet 

 can be retained on each and every irrigated acre during the season. 

 Of this quantity, which is exclusive of the precipitation, 0.01 foot in 

 depth, or 0.5 per cent, will be required during the first half of April; 



