CONTENTS 



PAGE 



Introduction 207 



Climatic conditions of southern Arizona 207 



Precipitation • 207 



Temperature and relative humidity 208 



Supply of irrigating water in Salt River valley 209 



Prevalent methods of orchardists 210 



Purpose and scope of experiments 211 



Above-ground operations and results 211 



During 1898-1899 211 



During 1899-1900 214 



During 1900-1901 ■. 216 



Discussion of principles involved 216 



Reasons for favorable results. 216 



Effects of summer irrigation 219 



Reasons for cultivation and weed destruction 220 



One summer irrigation considered advisable 221 



Underground investigations 222 



During 1899 , 222 



During 1900 222 



Table I : Results of moisture content determinations 223 



Discussion of moisture determinations 225 



Conditions found April 12, 1899 225 



Table of losses and gains 228 



Changes from April 12 to June 18 230 



Changes from June to September 230 



When trees use the most water 231 



Losses of water during entire season 231 



Effects of changes in level of ground water 232 



Gain in water during winter 1899-1900 234 



Loss of water during summer of 1900 234 



Moisture content changes of 1899 compared with those 



of 1900 235 



Amount of water needed by an orchard 236 



Summary and conclusions ■ • - 237 



