AGRICULTURAL ANALYSIS 



soils on which Crawley worked, are very strongly basic and hence 

 are in a condition better suited to fix and hold the phosphoric 

 acid than the acidic soils with which the chemist is usually called 

 upon to work. The obvious conclusion from an experimental 

 work of this kind is that in determining the power of any par- 

 ticular soil for holding the phosphoric acid applied to it, its 

 character, especially as regards its acidity or basicity, should be 

 carefully considered. 



245. Absorption of Phosphoric Acid of Superphosphates. 42 Mr. 

 Joffre states that contrary to what is usually thought, the com- 

 binations soluble in water appear to be absorbed by vege- 

 tation. The proportion absorbed is, without doubt, very small, 

 but it may have a very great importance because the absorption 

 takes place at a moment when the plants have used up the ma- 

 terial in the seed and have not yet developed sufficiently to evapo- 

 rate the large quantity of water and to be able thus to extract from 

 the soil the useful substances, difficultly soluble, which there 

 exist. 



This theory explains perfectly the results of the remarkable 

 researches of Schloesing and Prunet who have found that, when 

 fertilizers are planted in the rows, they produce greater effects 

 than when they are mixed with the soil. This evidence depends 

 upon the fact that when they are planted in rows, they become 

 soluble less rapidly and the plants thus have more time to absorb 

 the combinations of phosphoric acid soluble in water. 



On page 698 of the same volume, Joffre continues the dis- 

 cussion of the subject. In this communication he has subjected 

 to field experiments, the operations which he has previously con- 

 ducted in the laboratory. He says: "Moreover, in the culture 

 experiment made in pure sand where there was nothing which 

 could produce insolubility of phosphate soluble in water and 

 where it is seen that this body causes an increase in the crops, it is 

 necessary to admit that the combinations of phosphoric acid solu- 

 ble in water enter into the plant and are assimilated there. I 

 have not said that insoluble phosphate is without utility in agricul- 

 ture. It produces, indeed, in certain earth effects which are as 

 Bulletin de la Socit chitnique de Paris, 1895, [3], 13 : 522. 



