UNFAVORABLE FACTORS 



83 



If all the staves were as high as the concrete sides of the tank, 

 the tank would then hold its greatest amount of water. If all the 

 fertility factors were most favorable, the soil would have power 

 for producing maximum yields. 



Just as the water-holding capacity of the tank may be limited 

 by the shortest stave, so fertility or the productive power of a 

 soil may be limited or brought to naught by one deficient element 

 or an unfavorable soil condition. Thus it is possible for a soil to 



FIQ. 33. Soil fertility illustrated. Just as the water-holding capacity of the tank may 

 be limited by the shortest stave, so fertility or the productive power of a soil may be limited 

 or brought to naught by one deficient element or an unfavorable condition. 



lose its fertility or productive power through the depletion or loss 

 of a single fertilizing element. 



Unfavorable Factors. Many soils are unproductive because 

 one or more factors are unfavorable. In case of drained peat, the 

 common cause of poor crops, or failures, is the lack of potassium. 

 This condition can be corrected through the use of potash fertil- 

 izers or in terms in harmony with Fig. 33, the shortest staves 

 may be lengthened by applying fertilizers carrying potassium. 



In many instances, poor yields and failures in growing alfalfa, 



