SAVING WATER BY CULTIVATION 63 



row while it leaves the top soil loose and open. The merit 

 in this process is that the loose top soil permits the easy 

 entrance of water into the soil and also acts as a mulch 

 to prevent evaporation. To accomplish such sub-sur- 

 face packing the Campbell machine may be used, or the 

 soil may be thoroughly cross-disked. 



Rolling, whether on top or below the surface, is of 

 small and questionable value in any system of irriga- 

 tion practice. 



REFERENCES 



BRIGGS, LYMAN J., and BELZ, J. O. Dry-Farming in Relation to 



Rainfall and Evaporation. United States Bureau of Plant 



Industry, Bulletin No. 188 (1911). 

 BUCKINGHAM, EDGAR. Contributions to Our Knowledge of the 



Aeration of Soils. United States Bureau of Soils, Bulletin 



No. 25 (1904). 

 BUCKINGHAM, EDGAR. Studies on the Movement of Soil Moisture 



United States Bureau of Soils, Bulletin No. 38 (1907). 

 FORTIER, SAMUEL. Evaporation Losses in Irrigation and Water 



Requirements of Crops. United States Office of Experiment 



Stations, Bulletin No. 177 (1907). 

 FORTIER, SAMUEL, and BECKETT, S. H. Evaporation from Irrigated 



Soils. United States Office of Experiment Stations, Bulletin 



No. 248 (1912). 

 WHITNEY, MILTON, and CAMERON, F. K. Investigations in Soil 



Fertility. United States Bureau of Soils, Bulletin No. 23 (1904). 

 WIDTSOE, J. A. Factors Influencing Evaporation and Transpira- 

 tion. Utah Experiment Station, Bulletin No. 105 (1909). 

 WIDTSOE, J. A., and MCLAUGHLIN, W. W. The Movement of Water 



in Irrigated Soils. Utah Experiment Station, Bulletin No. 115 



(1912). 

 WIDTSOE, J. A. Dry-Farming. Chapter VIII (1911). 



