PART THIRD 



POTASH IN FERTILIZING MATERIALS AND 

 FERTILIZERS 



414. Introduction. The potash present in unfertilized soils 

 has been derived from the decay of rocks containing potash min- 

 erals. Among these potash producers feldspars are perhaps the 

 most important. For a discussion of the nature of their decom- 

 position and the causes producing it, the first part of Volume I 

 may be consulted. Potash is quite as extensively distributed as 

 phosphoric acid, and no true soils are without it in some propor- 

 tion. Its presence is necessary to plant growth and it forms, in 

 combination with organic and mineral acids, an essential part of 

 the vegetable organism, existing in exceptionally rich quantities 

 in the seeds. It is possible that potash salts, such as the chlorid. 

 sulfate, and phosphate, may be assimilated as such, but, as with 

 other compounds, we must not deny to the plant the remarkable 

 faculty of being able to decompose its most stable salts and to 

 form from the fragments thus produced entirely new compounds. 

 This is certainly true of the potash compounds existing in plants 

 in combination with organic acids. The potash which is assim- 

 ilated by plants exists in the soil chiefly in a mineral state, and 

 that added as fertilizer is chiefly in the same condition. That 

 part of the potash in a soil arising directly from the decomposi- 

 tion of vegetable matters may exist partly in organic combina- 

 tion, but this portion, in comparison with the total quantity ab- 

 sorbed by the plant, is insignificant. 



It is then safe to assume that at least a considerable part of 

 the potash absorbed by the plant is changed from its original 

 form of combination by the vegetable biochemical forces, and is 

 finally incorporated in the plant tissues in forms determined by 

 the processes of vegetable metabolism. 



The analyst is not often called upon to investigate the forms 



