8o Journal of Agricultural Research voI.xv.no. 2 



portion of the same soil which has, during the same period, received no 

 fertilizer addition of any kind, but which has been tilled and cropped the 

 same, gives the following results: 



(i) The proportion of the potash dissolved by strong, hot acid is some- 

 what greater where the potash dressings have been used. In weak 

 solvents (distilled water, carbonated water, weak solution of ammonium 

 chloiid, and N/^ hydrochloric acid) twice as much potash is dissolved 

 in a short time at moderate temperatures from the fertilized soil as these 

 solvents take, under the same solution conditions, from the unfertilized 

 soil. 



(2) Of the w^eak solvents named, the TV/j acid dissolves the most 

 potash. The quantities of this element dissolved by the other weak 

 solvents, differ, of course, with the solvent; but each forms in each soil 

 the same percentage proportion of the amount dissolved by the N/^ 

 acid — that is, the solvent effects are parallel. 



(3) The potash dissolved upon a second extraction with ammonium- 

 chlorid solution is very much less than is dissolved by the first extraction 

 with this solvent, and the quantities are practically the same for each 

 soil; whereas that removed by the first extraction from the soil dressed 

 with potash is twice as great as the amount taken from the unfertiUzed 

 soil. 



(4) The clays and nonclays of these soils, after separation by sedi- 

 mentation in water, show the following characteristics as to potash 

 content and solubility : The clays contain less potash than the nonclays. 

 The clay of the potash soil is richer in potash than that of the unfertilized 

 soil. The same is true, but in less degree, of its nonclay fraction. Unit 

 weights of the clays give up much more potash to ammonium-chlorid 

 solution than unit weights of the nonclays. Both fractions of the 

 potash-dressed soil exceed those of the unfertilized soil in this respect, 

 but the clays much more than the nonclays. Unit surface areas of the 

 clay particles, as conventionally calculated, give up much less potash 

 to the solution than equal surface areas of the nonclays. This may, 

 however, be due to a reduction of free-clay surface to less than the con- 

 ventional area by cementing of the particles in drying, or because of the 

 flocculating influence of the saline solvent used. 



(5) The soil is naturally rich in potash, and potash dressings cause 

 little or no crop increase. These dressings are followed, however, by an 

 increase in the amounts of potash taken up by the crops. Five crops 

 examined all show this increase. On the average "for a rotation, the 

 crops harvested from the land dressed with potash carry off in a given 

 weight of harvest, 40 per cent more potash than a like harvest weight 

 from the unfertilized land contains — that is, both chemical solvent and 

 plant agiee in indicating a higher availability for at least part of the 

 potash in the potash-dressed soil. Moreover, the crops grown the 



