10 



and is susceptible of taking a high polish. When wet the lumps are 

 very plastic and sticky, making a refractory soil which it is very dif- 

 ficult to cultivate.- Upon drying the soil becomes very hard and 

 cracked. Sorghum and millet were grown this year on several hun- 

 dred acres of this land in the vicinity of Calexico which produced 

 good crops. The sorghum, however, was the best, the yield being 

 or 8 tons to the acre. 



Cultivation of this clay soil will be very difficult. A similar soil is 

 found in the Salt River Valley as a phase of the Glendale loess and is 

 localh' known as "slickens." The farmers of that neighborhood have 

 considerable difficult}' in managing this soil and it is not a- refractory 

 as much of the Imperial clay. Either annual crops or crops which 

 can be cultivated throughout the growing season are productive of 

 best results on this soil, for the heavy and hard crusts need to be 

 broken up and thoroughly pulverized occasionally. Alfalfa does not 

 do well on such a soil, for the crusts seem too hard and the soil too 

 dense and impenetrable to permit the constant extension of the tine 

 rootlets so essential to permanency in an alfalfa tield. Deep plowing 

 and thorough cultivation will in a few years greatly improve this soil. 



Aside from the difficulties in the physical properties of the soil, the 

 greater part of it contains too much alkali to warrant its continued 

 cultivation. Two or three crops may be taken off the land, but the 

 rise of the alkali is almost inevitable, and the cultivation of soils con- 

 taining more than 0.4 per cent alkali is not recommended. 



In the area surveyed there were 23,000 acres of this soil. Of this, 

 3 per cent carried less than 0.2 per cent alkali, 43 per cent carried from 

 0.2 to 0.4 per cent, and 54 per cent had more than 0.4 per cent alkali. 



ALKALI IN THE SOIL. 



By popular usage any harmful accumulation in the soil of salts of 

 any kind is referred to as alkali, distinctions being made between dis- 

 tricts containing a large amount of sodium carbonate and those which 

 do not. The sodium carbonate areas are popularly called ''black 

 alkali" areas, and all others ""white alkali" areas. The white alkali 

 salts are usually found associated with the sodium carbonate in black 

 alkali areas, while in the white alkali regions there* is usually a pre- 

 dominance of the sulphates or chlorides, with smaller amounts of 

 other salts. So far as is yet known, the amount of white alkali that 

 crops will withstand is influenced more by the presence or absence of 

 lime as a constituent of the soil than by the chemical composition of 

 the salts. It has been determined by experiment, both in the field 

 and in the laboratory, that where there is an excess of lime in the soil 

 in the form of sulphate or carbonate, plants will withstand a greater 

 percentage of alkali than where the lime contend is small. In the 

 Colorado Desert gypsum (sulphate of lime) and carbonate of lime are 

 nearly always present in the soil. 



