Oct. 4, 1915 



Effect of Alkali Salts in Soils on Crops 



49 



makes it impossible to say exactly what are the practical limits of 

 alkalies. 



In getting the limits given below it was considered that when alkali 

 retarded germination and growth to about half what they were in soils 

 without alkali the practical limit had been reached. Certainly it would 

 not be profitable to use a soil where alkali decreased yields below half 

 normal. 



Figures 46 and 47 show the practical limits of growth of wheat in 

 loam and sand for 13 different salts. It will be noted that these salts 

 bear a similar relation to each other in both kinds of soil, although only 

 about half as much alkali is required in sand to reach the toxic limit as 

 in loam. One of the most striking features about the diagram is the 

 fact that in sand the carbonates are proportionately more toxic when 

 compared with other salts than they are in loam. 



Fig. 46.— Diagram showing the percentage of alkali salt in loam soil giving about half normal germination 

 and production of dry matter in wheat. 



Loam having 0.3 per cent and sand having 0.2 per cent of sodium 

 chlorid contain a limit of this salt for the profitable production of crops. 

 The other chlorids may be somewhat higher, while the nitrates may be 

 about 0.1 per cent higher than the chlorids. On loam crops grow well 

 with as high as i per cent of the sulphates, while in sand from 0.5 to 

 0.7 per cent of the sulphates is injurious. 



Figure 48 gives a comparison of the resistance of barley, oats, wheat, 

 alfalfa, sugar beets, com, and Canada field peas for sodium chlorid, 

 sodium carbonate, and sodium sulphate in loam. Barley can withstand 

 0.5 per cent of sodium chlorid, i per cent of sodium carbonate, and more 

 than I per cent of sodium sulphate. All crops in the test except oats, 

 sugar beets, corn, and field peas produced more than half normal growth 

 where i per cent of sodium sulphate was present. There was a great 

 difference in the resistance of various crops to sodium carbonate, the 



