The Colorado Potato Industry. ii 
and the hollow between the rows becomes deeper, thus ditching 
is more easily done. 
Ditching and irrigating are delayed as long as possible. The 
rule is not to irrigate if it can be avoided till the potatoes are in 
bloom or the tubers set. 
Ditching. The ditching is done with a narrow double 
mold board plow. Three horses are attached and the plow is 
run once in each row at about the depth of cultivation or ten to 
twelve inches. This ditching takes the place of one cultivation 
and if the ground is hard or if the first irrigation fills the ditches 
to any extent, the operation is repeated so as to make the ditches 
deep enough to keep the water below the surface of the potato 
ridges. 
Irrigation. .The details of irrigation depend upon the size 
and contour of the field to be irrigated. Many of the fields are 
arranged so that the rows are from one-fourth to one-half mile 
long. If the land slopes sufficiently and continuously across the 
field from the supply ditch, the problem is simple. At the first 
application the water is turned into a lateral at the head of the 
rows. A canvas dam is placed in the lateral so as to hold the 
water back and raise it into the rows. After the water has 
run in these rows a sufficient length of time to thoroughly wet 
the soil, the canvas dam is pulled out and reset farther down the 
lateral, and the water is stopped by blocking the heads of the 
irrigated rows with soil. In large fields the water is run in al¬ 
ternate rows only. 
The head of water let into the rows depends upon the slope 
and length of rows. If the rows are short and the incline steep, 
the head must be small or the stream will reach the far side so 
quickly that enough water will not be used to thoroughly wet 
the soil. On the other hand, if the rows are long and the land 
nearly level the head of water is increased so as to force it along 
the rows faster, or a transverse ditch is cut through the middle 
of the field so as to shorten the distance that the water has to 
flow. If ridges occur in the field transverse ditches are run along 
at their top and irrigating is done both ways from it. When 
the water has run in the ditches till it seeps through to the unirri¬ 
gated row, the soil is sufficiently wet. At the second irrigation 
the water is run in the rows not irrigated the first time. As 
the vines become large, the irrigation becomes more difficult owing 
to the lodging of the vines in the ditches, till at last , considerable 
trouble is sometimes experienced to get the water through. On 
the other hand as the vines grow larger the soil is more protected 
from the sun so that the evaporation becomes less and the plants 
suffer less from want of water. 
