Winter Irrigation of Deciduous Orchards. 235 



also, that a few of the trees near the center of the orchard had 

 died when young, leaving a vacant space for the center of which 

 it was thought no moisture would he withdrawn by the trees. 



When the samples were taken from the covered area October 

 9th it proved, as has been stated previously, that the surround- 

 ing trees had put out additional rootlets and caused all the soil, 

 with the exception of a few surface inches, to be as dry as that of 

 the adjacent uncovered area. While the soil samples from the va- 

 cant space showed the presence of considerably more moisture 

 than in the part occupied by trees, a little reflection resulted in 

 the conclusion that no definite calculations could be based on the 

 results, as it was not known during what part of the summer any 

 particular portion of the losses occurred, in either section. It 

 seemed evident that the comparative losses should have been de- 

 termined, from week to week, since moisture that trees (had they 

 been present) might have withdrawn from the upper five or six 

 feet early in the season, would be lost from the vacant area, by 

 capillary action and evaporation, during a later part of the sum- 

 mer. Samples should have been taken also from the covered area 

 at least once a month, in order to determine the comparative 

 changes that were occurring. It is hoped that experiments now 

 under way in this orchard will bring results that will throw some 

 light at least upon this problem as to how much water orchard 

 trees use under the conditions existing in the vicinity of Phoenix. 



Moisture Content Changes of 1899 Compared with those of 1900. 



By reference to Tables I and II, and to Figs. 8 and 9, it will 

 be seen that each foot of the 25-foot column lost moisture during 

 the summer of 1900, instead of the stratum between the 20th and 

 the 26th foot, gaining, as was the case the previous year. As 

 Fig. 8 shows diagrammatically, the decrease in moisture content 

 was quite regular from the 16th to the 26th foot. This difference 

 between what occurred during the summer of 1899 and w 7 hat 

 occurred during the summer of 1900 was undoubtedly due to the 

 fact that the comparatively dry stratum encountered between the 

 20th and the 26th foot, April 1899, had become about as moist as 

 it could remain. In other words, this stratum was, at the begin- 



