38 SCIENTIFIC REPORTS OF THE AGRICULTURAL RESEARCH 



mediately formed in situ, thus limiting the distribution Of 

 the phosphoric acid through the soil and causing the 

 superphosphate to have a very localized value. On' the 

 other hand, in non-calcareous soils it would appear probable 

 that the range of action would be wider and the distribu- 

 tion more uniform throughout the mass of the soil. To test 

 this, the distribution of the phosphoric acid of different 

 phosphates by percolation through columns of the type soils 

 was studied. The results showed that the distribution of 

 superphosphate through a non calcareous soil is of an 

 uniform type. The phosphoric acid penetrates to a con- 

 siderable depth and consequently the effect of applications 

 of superphosphate to such soils is widespread. On the 

 other hand, the distribution of superphosphate in the case 

 of calcareous soils is of a non-uniform type, the major por- 

 tion of the phosphoric acid being held in the top layers of 

 the soil. Consequently, the application of superphosphate 

 to these soils has a very restricted effect and has therefore 

 probably much less efficiency than equivalent amounts ap- 

 plied to soils of the opposite type. In proportion to the 

 amount of superphosphate applied to the columns of soil, 

 the soil solution of calcareous soils contains a much less 

 concentration of. phosphoric acid than in the case of non- 

 calcareous soils. In the light of present knowledge this can 

 only mean that the phosphoric acid retained is in a much 

 more available form in the latter soils. 



• It has further been found that the presence of even 5 

 per cent, of calcium carbonate in a non-calcareous soil 

 restricts the diffusion of the phosphoric acid of super- 

 phosphate. In fact, in such a case the phosphoric acid is 

 practically completely retained in the top few inches. This 

 shows that calcium carbonate is the determining agent. 



On the other hand, it has been demonstrated that the 

 distribution of the phosphoric acid of those soluble phos- 

 phates which are without action on calcium carbonate, 

 through a column of soil is of an uniform type even in 

 highly calcareous soils, and that the phosphoric 8[cid pene- 

 trates to a considerable depth. It would, therefore, seem 



