IRRIGATION REQUIREMENTS OF THE GREAT BASIN 
31 
The first of the series of three experiments was conducted on a 
field of red clover 11.6 acres in extent and irrigated in borders. The 
soil and subsoil are composed of sand, gravel, and cobbles, and are 
typical of this locality. During the latter part of August, when the 
second crop of clover was about 14 inches high, a strip of the field 
49.5 feet wide and 2,359 feet long was selected for the experiment. 
This strip was divided into seven equal parts, each 337 feet long, and 
a head of water of approximately 2% cubic feet per second was 
turned on at the upper end. The stream was allowed to flow unin- 
terruptedly over the entire length of the strip, the time being noted 
when the advance of the water reached each division. The results 
are summarized in Table 4. 
Table 4. — Time required to irrigate equal subdivisions of a strip of land in red 
clover near Rlgby, Idaho, and the quantity of water applied to each 
No. of division 
Length 
of 
division 
Area of 
division 
Time 
required 
to 
irrigate 
Quantity 
of water 
applied 
per acre 
1 
Feet 
337 
337 
337 
337 
337 
337 
337 
Acres 
0. 3835 
.3835 
.3835 
.3835 
.3835 
.3835 
.3835 
Ets. min. 
1 22 
1 50 
2 00 
2 30 
3 00 
6 00 
7 00 
Acre-feet 
0.2605 
2 
.3499 
3 
.3818 
4 _ 
.4772 
.5727 
8_ . . 
1.1454 
1. 3363 
Totals 
2,359 
2.6845 
23 42 
4.5238 
An alfalfa field containing 16.5 acres, located 7 miles southwest of 
Rigby, Idaho, was selected for the second experiment. Formerly 
this field had been irrigated in three border strips each 2,560 feet 
long. In order to determine the benefits, if any, to be derived from 
shorter runs, the middle strip was subdivided into three equal parts 
by the building of two extra head ditches, thus reducing the run to 
one-third its former length. The average quantity of water in each 
irrigation applied to each of the two outer strips was 1.25 acre-feet 
per acre, while that applied to the middle strip was 0.9 acre-foot per 
acre, thus effecting a saving in water of 28 per cent and securing a 
larger yield of alfalfa. 
The third experiment was conducted on a 16-acre oat field in the 
vicinity of the former experiments. The soil and subsoil were simi- 
lar in character. The field was irrigated by flooding in three par- 
allel border strips 90 feet wide subdivided into different lengths. 
The length of the run in the first strip was 428 feet, the second 857, 
and the third 2,570 feet. Each strip was given three irrigations, the 
first receiving a total of 2.9 acre-feet, the second 3.23 acre-feet, and 
the third 4.26 acre-feet per acre. The yields of the respective strips 
were 76.7, 63, and 74.7 bushels of oats. 
It is well to bear in mind that the length of run and the quantities 
of water absorbed by porous soils do not apply to the tight soils, 
since in applying water to the latter type it is difficult to secure suffi- 
cient penetration of moisture. One of the means used in moistening 
clay soils to the requisite depth is to apply a small head of water to a 
long border or furrow for a sufficient time to insure proper penetra- 
tion of the moisture, 
