20 CIRCULAR 112, BUREAU OF PLANT INDUSTRY. 



These results confirm those of the previous year as to the effect of 

 differences of soil texture upon the size and vigor of the plants, and 

 also give a more definite expression of the effect upon the fruitfulness 

 (number of bolls). There was apparently no consistent effect upon 

 the height of the first fruiting branch. 



It is evident, therefore, that in the absence of appreciable quantities 

 of alkali salts, the size, vigor, and fruitfulness of Egyptian cotton 

 plants in alluvial soils along the Colorado River is largely determined 

 by the depth of the layer of silt with its relatively high moisture 

 capacity and its doubtless greater supply of plant food. 



The very sandy soils have so low a moisture capacity that they 

 hold very little water even immediately after an irrigation and with 

 the customary intervals between irrigations they soon become so dry 

 that much of the time the plants are without available water. This 

 frequent condition of virtual drought seriously impairs the yield and 

 quantity of fiber produced in such soils. 



ALKALI CONTENT OF THE SOIL. 



In a previous publication l the results of observations on the 

 growth of Egyptian cotton plants hi alkali soil at Sacaton, on the 

 Gila River, hi southern Arizona, were summed up as follows: 



No plants grew at Sacaton in places where the average amount of alkali in the first 

 3 feet of soil was as high as 1.7 per cent. While resistant individual plants can pro- 

 duce a small amount of fairly good fiber in the presence of from one-half to 1 per cent 

 of alkali, it is probable that land containing considerably less than one-half of 1 per 

 cent must be selected in order to obtain anything like a full stand and the best quality 

 of fiber. The actual limit of safety remains to be determined. 



Since this statement was written, further observations upon the 

 alkali resistance of this plant were made at Sacaton, Ariz., hi 1910, 

 and at Bard, Cal., hi 1911. Even with these additional data the 

 quantity of alkali of a given composition which limits the successful 

 growing of Egyptian cotton can be stated only approximately. 2 



In a general way, however, the more recent observations confirm 

 the conclusion previously readied that Egyptian cotton is superior to 

 many other crop plants in its ability to endure an excess of salts hi 

 the soil. 



OBSERVATIONS AT SACATON, ARIZ. 3 



A portion of one of the fields planted to the Yuma variety of 

 Egyptian cotton was located where the soil contained more or less 

 salts and where as a consequence the stand was very irregular. The 



i Circular 29, Bureau of Plant Industry, entitled "Experiments with Egyptian cotton in 1908," 1909, 



p. 18. 



2 A discussion of the varying factors which make it difficult to determine in the field the limits for the 

 growth of a particular plant in the presence of alkali will be found in Farmers' Bulletin 446, entitled " The 

 choice of crops for alkali land," 1911, pp. 8 to 12. 



3 These were made in October, 1910, at a time when the cotton had begun to ripen in most parte of the 

 field. 



[Cir. 112] 



