820 EXPERIMENT STATION RECORD. [Vol.38 



" More moisture was held in the upper 6 ft. of spring-plowed than of fall- 

 plowed fallow. In years of high precipitation, moisture was stored to a depth 

 of 7 ft. in summer fallow, while in dry years it accumulated only to a depth 

 of 3 or 4 ft. Plowing both in the fall and in the spring did not store more 

 moisture than either spring or fall plowing alone. Practically the same amount 

 of moisture was found in land plowed shallow, deep, and subsoiled. 



" Cultivation of fall-plowed fallow by eradicating weeds and volunteer grain 

 conserved a great deal of moisture, but the cultivation of spring-plowed fallow 

 was of doubtful value. 



" Mulched fallow retained only slightly more moisture than fallow on which 

 the weeds were killed with a sharp hoe but not mulched ; hence, destroying 

 weeds is more important than maintaining a mulch in conserving moisture 

 in fallow land. Straw mulches were more efficient in preventing evaporation 

 than soil mulches. Deep mulching was more effective in retaining moisture in 

 spring-plowed fallow than in fall-plowed fallow. Fallow soil lost from 0.5 

 to 2 per cent in addition to the rainfall between spring and fall of the fallow 

 summer. 



" Continuously cropping to winter wheat did not deplete the moisture supply 

 to a depth of 10 ft. more thoroughly than alternate cropping. Although the 

 intertilled crops — corn, peas, and potatoes — used moisture to a^ depth of 5 ft.', 

 they did not dry the soil so thoroughly nor so deeply as did winter wheat. 



" Manure, especially when as much as 20 tons to the acre was added, increased 

 the water-holding capacity of cropped soil and slightly increased that of the 

 second foot in fallow. 



" Winter wheat used moisture to a depth of 6 ft. Stubble and fall-plowed 

 soils gained considerable moisture to a depth of 6 ft. between the fall of 1915 

 and, spring of 191G. Moisture penetrated deeper and more quickly in moist 

 than in dry soil. Summer tillage aided materially in conserving soil moisture. 



" At Nephi about 18 in. of water can be stored in the upper 6 ft. of soil. 

 Indications are that crops extend their roots into the lower soil layers for 

 water, but that little moisture is raised from great depths by capillarity in 

 this soil. It required from 0.5 to 1 in. of rain in the fall to connect the dry 

 surface soil on fallow with the moist soil below. 



" The minimum point to wliich winter wheat used water from the soil was 

 about 10 per cent. Hence, water above 10 per cent is available for this crop. 



" From 54 to 65 per cent of the precipitation falling between September 20 

 one year and the following September was found in the upper 6 ft. of soil. 

 Fallow land at Nephi averaged 17.5 per cent water in the upper 6 ft. of soil 

 in the fall. At seeding time about 6.4 in. of this moisture was available for 

 plants. During the winter after the fallow there is usually about 4 per cent, 

 or 3.5 in., of available moisture stored. Probably never more than 10 in. of 

 water in the upper 6 ft. of this soil is available for plant use. Even in the 

 best years following a fallow considerably less than one year's precipitation 

 was available for crops in the first 6 ft. of the soil." 



Soil moisture studies under irrigation, F. S. Harris and A. F. Bracken 

 (Utah Sta. Bui. 159 {1911), pp. 26, figs. 19).— This bulletin reports the results 

 of several thousand moisture determinations of cropped and uncropped field 

 soils during a number of years under irrigation, in a study of some of the prob- 

 lems of soil moisture movement and distribution under field conditions, includ- 

 ing experiments with potatoes and beets under irrigation, observations of mois- 

 ture conditions in furrow irrigation and after flooding, the effect of mulches in 

 conserving moisture, a comparison of cropped and fallow soils, and the effect 

 of manure. The work was conducted on a deep, rich clay loam, dark in color 



