On the grass plot, the moisture was extracted primarily 

 from the upper 2 or 3 feet. With such a large portion of the total 

 water use from such shallov/ depths, the inherent uncertainty of 

 surface neutron probe measurements assumes greater importance. It 

 has been concluded that the neutron scattering technique is not well- 

 suited for measuring evapo trans pi rat ion of grasses due to their 

 shallow moisture extraction patterns and frequent irrigations. Plan 

 have been made to use evapotranspirometers on this crop. 



On the alfalfa plot, ample tubes were sampled to obtain a 

 good estimate of moisture depletion. 



On the cotton plot, three sets of seven tubes each were 

 placed at the upper, middle, and lower ends of the 440- foot furrow 

 runs. The tubes were placed diagonally, crossing the rows, such 

 that the tubes were located in the plant row, and in the furrow 

 bottoms and furrow shoulders. The number of tubes was adequate to 

 determine moisture change with good precision. 



Cotton is not normally overirrigated, which is an advantag 

 in soil moisture depletion studies, since soil moisture movement is 

 not as much a problem in data interpretation as with most other crop 

 Portable water meters were used to measure the water applied to the 

 cotton. These measurements confirmed the seasonal depletion record 

 obtained from the neutron probe measurements. 



Evapo transpirometer Measurements 



Evapotranspirometers, sometimes referred to as lysimeters, 

 are instruments designed for the measurement of evapotranspiration. 

 They can be of various shapes, sizes, and designs. Essentially, 



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