Winter Irrigation of Deciduous Orchards. 219 



20th, 1900, revealed that at the depth often to sixteen feet, even, 

 young roots three to six inches long had already grown. At this 

 date there were few above-ground indications of growth, and it 

 would not have been supposed by making a casual observation 

 that the trees would make use of any water that might be applied. 

 While the air above-ground is still too cool to start the develop- 

 ment of the buds, the roots far beneath the surface are making a 

 growth that prepares the tree for the demand for water that the 

 leaves will make later. Thus, if the trees have an abundance of 

 water during the winter, the early root growth that will be made 

 will enable them to make a rapid growth as soon as the air above- 

 ground is warm enough to permit it. These facts account for the 

 rapid and vigorous growth that the winter-irrigated orchard made 

 in early spring, compared with those that had not been thus irri- 

 gated. 



Effects of Summer Irrigations. 



During the summer the climatic conditions and the demands 

 of the trees are quite the reverse of those of the winter. The high 

 temperatures and the low relative humidity cause such rapid evap- 

 oration that much of the water applied quickly escapes into the 

 atmosphere. The supply of water for irrigation being very low, 

 it is not ordinarily possible to apply sufficient quantities of water 

 to reach the deeply-seated roots of the tree. In summer a large 

 percentage of the water applied escapes directly from the soil with- 

 out passing through the trees. This is the case whether its sur- 

 face is cultivated (as should be done) and the upper few inches 

 loses all its moisture as a result ; or the soil is left to bake (as 

 should not be done) and not only the surface becomes dry and 

 hard, but a large amount passes up from below through the baked 

 soil. 



Summer irrigations are ordinarily surface irrigations. Only 

 a comparatively small percentage of the water applied becomes 

 available to the trees. While the surface may be wet, the roots 

 below may be in comparatively dry soil. Furthermore, from the 

 time that water is applied until a cultivation can take place, the 

 soil is practically sealed air-tight. This exclusion of air, for the 

 reasons stated above, retards the growth of the trees. Most of 



