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 by Table IX. 
TABLE 1X.—<Average volumes of water used on tracts with different types of soil. 
| 
Acre-feet used. 
No. Description. 
. Impervi-| Porous 
Allsoils. | Gus soils.| soils. 
el SALbtraetcimeludedan: Theinvesticavionas. 5. a ee 12.06 11.60 4. 66 
2 | Allalfalfa tracts included in the investigation _........._.......-..-- 3555 2.40 7.10 
3 | All grain tractsincluded in the investigation. ...................--.- | 1.56 32 3.19 
1 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 
souls. _ 
ee 
: ee volume of 
No. Kind of crop. | Nene water 
P applied 
| per acre 
A cre-feet 
a VV G ere rain Se sk Se Seine ee Ss Seep 15 0. 
Qe PSplin Sonat 6 ees eee Tae SE Sas Se eee ee 216 12a 
Sal SAU Aas eee 8 8 SSS i re os Se ek ee 79 : 2.43 
2 Ua bo Bes] AD RS \eo ne AR eh ee ar eae rege eee cee edge Spl ee Co ea sae et oe ee oon 13 13.02 
Eyal) TEQOT RS RO Sh oR eee ie, Aree oe een ene See ee eh eS oe sie ee ae iy; 17 
6s|sOrchard=-=3 OAS 5) Sak SNES A PO EE ee ee ee 11 1.45 
1 Waste not deducted from volume applied to part oftractsincluded. 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 fallmg 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 XI. 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 ‘hie average quantities applied — 
and yields produced from all plots on the same type of soil. 
