Arizona Agricultural Experimknt Station 405 



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wheat, the black alkali content will be held constant and other 

 factors varied until the influence of concomitant conditions has 

 been analyzed. To facilitate and shorten the time of this work 

 the present equipment for pot culture should be greatly increased. 

 Considerable difficulty was experienced in getting large sam- 

 ples of soil of desired alkali concentration to be used in these 

 experiments. At first field samples were taken, analyzed, and a 

 wagonload of soil from the selected spot brought to the laboratory. 

 This was dried, mixed by repeated shoveling on a cement floor, the 

 whole passed through a 2 m.m. sieve, again mixed, sampled and 

 analyzed. It was soon discovered that the field samples bore prac- 

 tically no relation to the large sample taken several days later 

 from the same spot. It was, therefore, necessary to take the large 

 samples without preliminary sampling and run the chance of their 

 being usable. 



SAMPLING FIELD SOILS 



The difficulties of sampling field soils have long been recognized, 

 and Lipman and his associates have shown that single field samples 

 are usually of little value. This is perhaps more true of alkali than 

 any other soil constituent. The movement of alkali in a field is 

 best described as billowy ; always in motion, shifting up and down 

 and laterally. During the year we were asked to inspect a farm 

 two miles south of Tucson. Surface appearances and the native 

 vegetation indicated the general presence of black alkali. Samples 

 of 'the first and secoud foot taken with the soil auger showed no 

 black alkali, but a fair amount of gypsum, or its equivalent in other 

 black alkali neutralizing salts. The analyses are shown as Nos. 

 7161 and 7162 in Table I. Since the analysis seemed contrary to 

 field indication, several days later a square yard was marked off 

 in the same field not far distant from the place where the auger 

 samples had been taken. The soil in this yard was removed care- 

 fully with trowels in two-inch layers to the depth of two feet, each 

 layer being thrown on a canvas and carefully sampled. The results 

 of the analyses are recorded in Table I, Nos. 7173 to 7184. The 

 surface layer was weakly of the gypsum type, changing into black 

 alkali in the third and fourth inch. The black alkali increased to a 

 maximum at the eighth inch, then decreased and changed back into 

 gypsum type at the sixteenth inch. In very large numbers of sam- 

 ples taken on small areas at the University Farm in connection 

 with field experiments in neutralizing black alkali with gypsum, 

 the most erratic results were obtained from adjacent borings. 



