IRRIGATION 
Fig: .3. Two Longi- 
Check-Furrow System. 
tudinal Furrows are Connected by Four Cross 
Rills for Each Tree. By putting check dams 
in the main furrows water can be held 
around the tree until taken up by the soil. 
sufficient to make the ground too wet for 
cultivation. 
Third: Placing the water below the 
surface, at a depth of from 1 to 3 feet, 
causes the roots to penetrate more deep- 
ly, to break up a new substratum of 
soil from which they extract food which 
is equivalent to extending over a much 
wider lateral surface, and therefore in- 
creasing the life of the tree besides in- 
creasing its rapidity of growth and bear- 
ing capacity. 
Fourth: In case of sub-irrigation from 
other lands this underground system is 
a drainage system as well as an irriga- 
ting system. 
Fifth: It tends to aerate the soil, for 
a certain amount of air passes through 
these underground ditches. 
Sixth: In case there is lack of water, 
this system will save enough above any 
other system known to enable us to grow 
cover crops which may be turned under 
at the proper period and thus fertilize the 
soil. 
These reasons urged by some who ad- 
vocate that system are not universally 
accepted; for on the other hand it is 
argued: 
First: That while there is less evap- 
1175 
oration, the loss by drainage is greater 
often than by evaporation. 
Second: While it is true that the tend- 
ency of the root system is toward the 
water, yet the feeding roots are natural- 
ly near the surface, and the water should 
be placed where they are. 
Third: In case a surface coating of 
manure is given, surface irrigation car- 
ries the fertility downward to the roots, 
whereas by the underground method, al- 
kali and other injurious substances are 
lifted to the surface by capillarity. 
FACTORS DETERMINING DUTY OF 
WATER 
FF. E. JONES 
The method of applying water is an 
important factor, for it has been found 
that furrow irrigation saves more water 
than the flooding method, and deep fur- 
rows have an advantage over shallow ones. 
Sub-irrigation is not practical, but re- 
sults in a great saving of water over the 
other methods of application. 
The method of planting enters into the 
amount of water required to mature the 
crop, for if crops are planted thinly, less 
water will be used; the amount of shade 
produced by the plant affects the evap- 
oration; and a cultivated crop will con- 
serve more moisture than an uncultivated 
one. 
Kind of tillage. In order to be most 
effective, cultivation must be promptly 
done after the water has been applied, 
for aS much water is lost in the first 24 
hours as is lost in the three days follow- 
ing. On heavy soils it is necessary some- 
times to wait two or three days. 
The kind of ditches. Small, shallow 
ditches result in a great percentage of 
loss. | 
The skill of the irrigator. This is one 
of the most important factors in deter- 
mining amount of water used. 
The amount and frequency of irriga- 
tion is a factor in the duty of water, for 
the land must be very level to make it 
possible to use as little as two inches of 
water at one irrigation. As a rule, a four 
or five inch irrigation will thoroughly 
wet a soil as far as the roots of ordin- 
ary crops go. Heavier amounts neces- 
