22 
Coj,ORADO Experimen'i' vSta'i'ton. 
IV. FIELD SrrUDIES OF HEAT AND SOAKAGE AND 
OTHER FIELD OBSERVATIONS. 
Tlirough the co-operation of the Board of Commissioners of 
Rio Grande county, who furnished the equipment, and of Mr. R. A. 
Chisholm, who cared for the work and took the yields, a field 
experiment to determine the best level of water for the sub-irriga¬ 
tion of potatoes was performed during the season of 1912 at Del 
Norte in a mellow, sandy loam soil. 
Four watertight galvanized iron tanks, four feet long, four feet 
deep and two feet wide (Figure 14) were set in the ground flush 
with the surface. In a corner of each a five-foot piece of corru¬ 
gated galvanized iron eavestrough piping was placed upright, the 
lower end being notched and placed on the bottom of the tank. To 
Figure 14.—Setting tanks for the study of the bpst water level for the sub¬ 
irrigation of potatoes. 
prevent clogging, the bottoms of fhe pipes were surrounded with a 
little pile of good-sized pebbles. Then the tanks were filled with 
earth, and Pearls were planted in each. 
A record of rainfall was kept, and deficiencies from an aver¬ 
age rainfall were made up by sprinkling a calculated amount of 
water upon the top of each tank. Additional water was run down 
the pipes, through which, also, the water levels were measured so 
