20 



BULLETIN 339,, U. S. DEPARTMENT OF AGRICULTURE. 



teristics: (1) The heavier soils, consisting of the clay, clay loams, 

 sandy loam, and fine sandy soils; and (2) the porous soils, consisting 

 of the coarse sandy and gravelly soils. The difference in the require- 

 ments of these two classes is illustrated hj Table IX. 





Table IX. — Average volumes of water used on tracts with 



different types of 



soil. 



/ 



Description. 



Acre-feet used. 



No. 



All soils. 



Impervi- 

 ous soils. 



Porous 

 soils. 



1 





12.06 

 3.35 

 1.56 



U.60 

 2.40 

 1.32 



4.66 



? 





7.10 



3 





3.19 









i Average low, due to fact that 74 per cent of tracts included was grain. 

 VARIATIONS IN IRRIGATION REQUIREMENTS OF CROPS. 



Table X is made up from the data secured on the medium clay 

 loam type of soils and shows, by crops, the average quantities applied 

 to the majority of the tracts of this type included in the investigation. 



Table X. — Average volumes of water applied to different crops on medium or clay loam 



soils. 



No. 



Kind of crop. 





Average 



Number 

 of plots. 



volume of 

 water 

 applied 





per acre. 





A cre-feet. 



15 



0.82 



216 



1.27 



79 



2.43 



13 



13.02 



17 



1.71 



11 



1.45 



Winter grain. 

 Spring grain. . 



Alfalfa 



Pastur.e 



Potatoes 



Orchard 



i Waste not deducted from volume applied to part of tracts included. Proper average quantity retained 

 approximately 2.8 acre-feet. 



Table X shows that different crops received different volumes of 

 water and that for the purpose of comparison they may be safely 

 divided into two classes — the winter and spring grains, potatoes, and 

 orchards falling in one class and the alfalfa and pasture falling in the 

 other. The table does not show the irrigation requirement for the 

 various crops on this type of soil, for some of the experiments showed 

 rather low yields, due to excessive or insufficient water. 



In order to throw light upon the irrigation requirements of the two 

 classes into which the crops observed may have been divided, the 

 data have been combined in a different manner in Table XL In 

 this table the yields from the plots making the maximum yields 

 from all experiments on clay loam soils, irrespective of the quantity 

 of water applied, are compared with the average quantities applied 

 and yields produced from all plots on the same type of soil. 



