14 



loss of phosphoric acid. Four soils loam, marl, clay and humus 

 were analysed and the total phosphoric acid compared with 

 that found in the drainage water. From the data thus obtained 

 the annual loss was estimated. The results showed a loss of 

 9146 grams per hectare in the case of the clay, while the humus 

 lost 21995 grams per hectare. The humus contained the smallest 

 per cent of phosphoric acid, but lost the largest amount. 



Schreiber 1 grew oats followed by turnips on sandy, humus, 

 and loamy soils using two fertilizers, viz : (i) a mixture of di- 

 calcium phosphate, calcium sulphate, and magnesium carbonate, 

 (2) a mixture of sodium phosphate, and carbonates of calcium 

 and magnesium. The first mixture gave the best results in 

 every case. The author thought that the diminished action in 

 the second case was due to the precipitation of phosphoric acid 

 by the carbonates of calcium and magnesium. His results with 

 peaty soils showed that the humus phosphoric acid, soluble in 

 alkaline ammonium citrate, was almost useless for vegetation. 

 In some cases the humus acted on the assimilable phosphoric 

 acid in a manner analagous to calcium carbonate. 



Joffre 2 made vegetation experiments to determine the relative 

 values of superphosphate, tri-calcium phosphate, and the ferric 

 phosphate obtained from a sample of manure containing very 

 little tri-calcium phosphate. Crops of mustard were grown on 

 plots which differed only with regard to the nature of the phos- 

 phate present. The ferric phosphate was little better than no 

 fertilizer, while the other phosphates gave a large increase. 



On mixing basic slag and superphosphate with soil, Smora- 

 wski and Jacobson 3 noticed that the phosphoric acid originally 

 soluble in water was rapidly converted to the citrate soluble 

 form, and this compound underwent no further change. 



Stoklasa 4 called attention to the fact that ferrous, salts in the 

 presence of phosphoric acid soluble in water, give rise to the 

 production of di-tri-ferric phosphate, unless there is an excess of 

 free phosphoric acid present. With soluble phosphoric acid 



1 Exp. Sta. Rec., 1895, 804. 



2 Bull. Soc. Chim., 1896, (3) 15, 42. 



3 Bied. Centr., 1896, 580. 



4 Ann. Agron., 1897, 23, 588. 



