4'iO EXPERIMENT STATION RKCORD. 



AIR— WATER— SOILS. 



Salt River Valley soils, R. II. Forbes {Arizona Sta. Bui. 28, pp. 

 66-99, map /). — This bulletin contains general remarks on the physical 

 and agricultural features of the Salt River Valley, the objects of soil 

 analysis, essential plant food, and interpretations of analyses, accom- 

 panied by tabulated analyses of 21 samples of soils from different parts 

 of Salt River Valley. 



The average composition of the soils examined is shown in rhe 

 following table: 



Average composition of Salt River Valley soils. 

 [In fine earl h. \\ ater free.] 



Per cent . 



Organic and volatile matter 3. 569 



Insoluble matter — sand, etc. 64. 575 



Soluble silica — from clay 13. 781 



Alumina — from clay 6. 433 



Iron oxid — from clay 4. 922 



Calcium oxid 2. 372 



Potassium oxid 821 



Sodium oxid . 425 



Magnesium oxid 1. 835 



Manganese oxid (Mn ; 0.i) .055 



Phosphoric acid 130 



Sulphuric acid . 059 



Carbon dioxid 1 1.025 



Chlorin 110 



Total 100. 112 



Humus . 1)50 



Nitrogen . 045 



Alkaline salts : 



Total soluble salts 167 



Sodium carbonate . 044 



Sodium sulphate .030 



Sodium chlorid . 041 



The results indicate that — 



"The soils of Salt River Valley, generally speaking, are amply supplied with the 

 more essential mineral | ash ) plaut foods, including lime, potash, and phosphoric acid. 



"Nitrogen and humus are undoubtedly deficient in quantity, and the addition of 

 these soil ingredients is desirable, perhaps imperative. 



"Alkaline salts are not prevalent in excessive amount except in occasional locali- 

 ties of limited area. The alkali is very 'white' in character and, consequently, its 

 injurious effects are minimum. 



"Probably the most serious difficulty with our virgin soils is a physical one. 

 Their dense, compact condition must be remedied by suitable methods of culture. 



"The cheapest and best methods of supplying the lack of humus and nitrogen, 

 and of improving the tilth and water-holding power of these soils is by growing 



1 This amount of carbon dioxid calculates to 2.33 per cent of carbonate of lime. 



