Winter Irrigation of Deciduous Orchards. 239 



14. The surface earth-mulch (which can be secured only by 

 cultivation) conserves the moisture stored in soil by checking 

 capillary action, and by preventing evaporation from all the soil 

 except the mulch itself; and it also permits air to enter the sub- 

 soil freely. 



15. The results of the underground investigations illus- 

 trated, among other things, the superior ability of fine soils to 

 absorb and retain moisture, and the inability of coarse soils lying 

 next to fine soil to long retain much water. 



16. The moisture content of the upper 25 feet of soil was 

 effected appreciably by above-ground operations and local climatic 

 conditions. 



17. The ground water evidently affects the moisture content 

 of clay eight or ten feet above it, the per cent of water in the 

 respective feet of that stratum decreasing as the water level falls, 

 and increasing as the water level rises. 



1-8. Growth of rootlets begins on deciduous trees, in our 

 climate, about a month before there are indications of growth 

 above-ground. 



19. The set of samples taken June, 1899, showed that about 



15 inches of water had been lost from the upper 25 feet (of which 

 the upper five feet lost about eight inches), and that from the 16th 

 and 17th feet considerable water had percolated into the drier soil 

 below. 



20. From June 18 to September 30 there was a loss of but 

 a little over three inches of water from the upper 25 feet, of which 

 the upper five feet lost a little over two inches. 



21. The total loss of water from the upper 25 feet, during 

 the spring, summer and autumn of 1899 was about 20 inches, of 

 which about 80 per cent was lost the first three months, about 



16 per cent the next three, and only about 4 per cent the last 

 three months. 



22. Deciduous orchards use and need the major part of the 

 water supply during spring and early summer, which need can 

 best be supplied in most of southern Arizona by filling the subsoil 

 with water during winter. 



