MANURES AND MANURING 



14 1 9 



Table IV. — Relation of per cent of crop area in perennial grass to crop 

 index in Chester Co. Pa. (1914 survey). 



Table V. — Average percentage of area of intertilled crops, annual crops not 

 intertilled, and perennial grass, Chester Co. Pa., (1914 survey). 



(i) The figures for this column are derived from a 1912 survey. 

 (2) All hay crops including annuiUs. 



1063- "Tetra phosphate". — V'inassa, G. (Turin Agricultural Experiment Station) in Le 

 Slazioni Spcrimcntali Agrarie Italiane, \o\. XLIX, Nos. 7-8, pp. 357-365. Modena, 1916. 



" Tetraphosphate " is a new fertiliser recently put on the market, 

 and has been suggested as a substitute for basic slag. It is prepared b}' 

 mixing powdered phosphorite with carbonates of the alkaline earths (at the 

 rate of 6 per cent by weight of the carbonates) and heating the mixture 

 to 400" C. in special ovens. The mass is then moistened and inert bodies 

 are added till a substance containing 20 per cent of total phosphoric acid 

 is obtained. The finished product is a drj^ greyish-white powder, al- 

 most insoluble in water with which it gives an alkaline reaction, and partly 

 soluble in acids which cause an evolution of carbon dioxide. 



" Tetraphosphate " was treated with a number of solutions and the 

 solubility of its phosphoric acid was determined ; similar tests with Sfax 

 phosphorite were carried on at the same time. The results are given below. 



M.VNURES 

 -VND M.VNURING 



