234 Bulletin 37. 



ter level fell. Thus, it seems that the upper stratum to a depth 

 of about 25 feet was influenced by above-ground operations and 

 conditions, while the soil below was influenced only or principally 

 by the changes -in the ground water level. Investigations after 

 the heavier precipitation of the past winter will throw additional 

 light on this subject. 



Gain in Water During Winter iSgo-igoo. 



During the winter of 1899- 1900 each 25-foot column gained 

 1 25 pounds, or an equivalent of two feet of water. The gain being 

 greater than the loss during the preceding summer, the soil at 

 the end of the irrigating season, March 12th, was moister than 

 at the same time the previous spring. This gain is one foot less 

 than the depth given on a preceding page as to the amount ap- 

 plied. This does not mean that a foot of the water applied was 

 lost by evaporation and percolation during the winter. For it is 

 to be remembered that it was ascertained during the winter of 

 1899 that the growth of rootlets begins early in February. The 

 production of these rootlets, the rise of sap in the tree, the swell- 

 ing of the flower and leaf buds, and the putting forth of bloom 

 and early leaves (as had some of these trees when the samples 

 were taken ) all mean the withdrawal of water from the soil. 



Loss of Water During Summer of /goo. 



It will be observed that the total loss of moisture between 

 March 9th and October 8th was a little greater than that given 

 for the previous summer. This was undoubtedly due to the fact 

 that the samples were taken earlier in the growing season than 

 they were the previous spring. Experiments were planned and 

 inaugurated during the spring of 1900 to ascertain how much of 

 the total loss of moisture would be due to withdrawal by the 

 trees, and how much would escape directly from the soil. But it 

 developed that the methods pursued were not adequate. As has 

 been stated, one space between four trees was covered with an 

 air-tight sheet of metal bordered with four-inch strips that were 

 sunk into the soil. The purpose of this was to prevent the escape 

 of moisture directlv from the soil in that section. It happened 



