212 CROPS FOR ALKALI LAND 



Jensen and Mackie (15) place the limit of profitable pro- 

 duction below 500 parts per million. The quantity of 

 sodium chloride that may be tolerated without notable 

 injury to wheat has been placed at from 100 to about 

 5000 parts per million by the various investigators. Few 

 observations have been made where sodium chloride or 

 sodium sulphate were the main salts. Traphagen (29) 

 states that the danger limit for wheat when the salts 

 consist of sulphates, two-thirds sodium sulphate, and the 

 rest magnesium sulphate is about 10,000 parts per million. 

 Considering only the sodium sulphate, this estimate is 

 nearly the same as the figures of Shutt (26) and the au- 

 thor (6), but much above these of Loughridge (19). It is 

 probable that the great discrepancies shown in these ob- 

 servations are partly due to a number of factors such as 

 the nature of the soils, mixtures of the salts, and feeding 

 zone of the roots. The variety of grain, as indicated in 

 the seedling tests noted in Chapter V, would probably 

 have some influence but not so much as the figures indicate. 

 Barley is the high-yielding grain of the West which 

 corresponds to corn in the central states. It is commonly 

 looked upon as being the most tolerant of the ordinary 

 grains for alkali. A number of observations have in- 

 dicated that this crop grows practically unhindered with 

 2000 to 4000 parts per million of white alkali and that it 

 frequently produces a good crop of grain with as much as 

 6000 parts per million of white alkali in the soil. When 

 grown as a forage crop, there will be a satisfactory yield 

 when the soil contains from 6000 to 8000 parts per million, 

 provided the seedbed is kept fairly free at first, according 

 to Kearney (17). Jensen and Mackie (15) found a poor 

 stand of barley on soil containing 500 parts per million 

 of sodium carbonate, but Holmes (14) states that this 



