from the outwash of the Sierra Nevada Ranre at the southern end of 

 the valley. The land slopes to the southwest at the plot area at 

 about 30 feet per mile (0.6 percent). 



Irrigation in the area is supplied from deep wells 

 lifting water several hundred feet. All of the Arvin plots are 

 located on Hesperia fine, sandy loam. This soil has no apparent 

 clay or cemented layers. Moisture drainage is good, Noncontinuous 

 silt layers and pockets of silt of varying thickness are found 

 from 3 feet down to 22 feet below the surface. Plot sites were 

 located where the least amount of silt layers are found. Sur- 

 rounding the sampling areas were irrigated orchards, vineyards, 

 alfalfa, cotton, and other crops. The irrigated area extends 20 

 miles to the north, 15 miles to the east, kO miles to the south, 

 and 60 miles to the west. 



Four crops, cotton, alfalfa, plum orchard, and fescue 

 grass, were sampled. All sites were irrigated by furrow or border 

 methods. In order to obtain reasonably precise data, more than 

 20 sampling tubes were installed on the cotton and alfalfa. Six 

 tubes each were installed on the plums and grass plots for ex- 

 ploratory purposes, the intent being to determine moisture extrac- 

 tion patterns. 



The plum orchard is planted on a 24-foot square pattern. 

 Water is applied to five or six straight furrows running in one 

 direction. Results of the neutron probe measurements indicate that 

 the extraction of moisture is greatest from the furrov/ area near 

 the trees, intermediate from the middle furrows, and least from the 

 soil in the tree rov;s. Extraction was noted to a depth of l6 feet. 

 Depth of extraction probably depends largely on Irrigation practices, 



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