WATER CAPACITY OF SOILS 



155 



Table XXIII, continued 



But all of this moisture is not available to crops. 

 The third column gives the per cent of water in these 

 soils which would be unavailable, or the point at which 

 plants would ordinarily wilt. This per cent, or amount 

 of water at which plants are just able to survive, is 

 termed the minimum or critical moisture content, while 

 the highest per cent at which the plant will survive 

 is termed the maximum moisture content. The inter- 

 mediate point at which any crop makes its best growth 

 is termed the optimum moisture content. 



Each of these points, or moisture conditions, is very 

 definite for each soil and for each crop. The minimum 

 for different crops on the same soil is not the same as 

 the results of a number of investigators have shown. 

 Storer reports that, on a calcareous soil having a hygro- 

 scopic capacity of 5.2 per cent, the minimum for grasses 

 was 9.85 per cent, and for legumes 10.95 per cent; while, 

 on peat (muck) with a hygroscopicity of 42.3 per cent, 

 the grasses suffered at 50.87 per cent of moisture, 



