Under normal precipitation the variety of crops which can be successfully grown in the West is limited. Of necessity, irrigation was practised and with it came many complex problems. The water requirements of different crops, the water-holding capacity of soils, the movement of soil moisture, and numerous other related problems have given themselves up for investigational work.
Harris, F. S. and Brakcen, A. F., "Bulletin No. 159 - Soil Moisture Studies Under Irrigation" (1917). UAES Bulletins. Paper 125.