156 EXPERIMENTAL FARMS 



1-2 EDWARD VII., A. 1902 



Its fertilizing value may be said to depend upon two factors : the percentage of phos- 

 phoric acid present, and the degree of fineness to which the slag has been ground. Al- 

 though only introduced into Canada some three years ago, it is fast growing in favour, 

 being found a useful source of phosphoric acid, more especially for sour soils, those 

 rich in humus, and those deficient in lime.* 



Basic slags, as might be expected, will vary in composition, but usually they con- 

 tain between 15 per cent and 20 per cent of phosphoric acid, of which we have found 

 about two-thirds is soluble in a 1 per cent solution of citric acid, and hence may be 

 considered as more or less ' immediately available.' There is also present a certain 

 amount of free lime, generally about 15 per cent, and it is this fact that gives the slag 

 an additional value for soils of the character we have mentioned. With respect to the 

 fineness of grinding already referred to, it has been ascertained that the solubility of 

 the phosphoric acid, in other words, the activity of the fertilizer, is in proportion to 

 the degree of fineness — the coarser the slag the slower does it set free its phosphoric 

 acid for crop use. 



To obtain data upon the degree of availability of its phosphoric acid, certain la- 

 boratory experiments were made upon a sample of ' Thomas' Phosphate Flour,' forward- 

 ed by a correspondent in Nova Scotia, in which province, as well as in New Brunswick, 

 we learn this fertilizer has a large sale. It was in the form of a fine, almost impalpable 

 powder. 



The total phosphoric acid present was found to be 18 -23 per cent. 



Citric Acid, 1 per cent. — One gram of the fertilizer was shaken up with 100 c.c. 

 of 1 per cent citric acid solution (a solvent presumed to be approximately equal to the 

 exudations of roots in strength or power of rendering soluble mineral plant food) for 

 two hours at ordinary temperatures and filtered. Analysis showed that 10 -33 per cent 

 phosphoric acid had entered into solution. In the next experiment 1 gram of the fer- 

 tilizer was shaken up with 200 c.c. of the 1 per cent citric acid solution, time and tem- 

 perature being the same as in the preceding trial. Phosphoric acid to the extent of 

 11 -55 per cent had been dissolved. 



Further investigation will be made to ascertain, if possible, the limit of solubility 

 or availability, but these data are in themselves sufficient to indicate that a very large 

 proportion of the phosphoric acid may be rendered assimilable during the first season 

 of application. Further, it is evident that this fertilizer is not, as thought by some, to 

 be considered in the same category, as regards availability, with ' phosphate rock,' 

 4 floats,' &c, forms of phosphoric acid which can scarcely be used directly owing to 

 their very slow solution in the soil. 



In England and Germany, countries now using large quantities of this fertilizer 

 (Basic slag), especially as a top dressing for grass lands, the relative value of a sample 

 is determined by the amount of phosphoric acid soluble in a 2 per cent citric acid 

 solution (Wagner's method). By this stronger solvent we obtained from the sample 

 under consideration 12 "77 per cent phosphoric acid. 



WOOD-ASHES. 



In the course of the examination of many soils from British Columbia, it has been 

 made evident in a number of instances that it would be advisable to apply lime, either 

 to supply a deficiency in this element of food, to serve as a correction for sourness or 

 to aid in the conversion of certain injurious iron compounds found in badly drained 

 lands. To this end we have advised the application of wood-ashes, which would not only 

 furnish lime, but also notable amounts of those important constituei 1 ^ of plant food — 

 potash and phosphoric acid — but to this suggestion we almost invariably receive the 

 reply that such are not obtainable. The common and, indeed, almost universal im- 

 pression among farmers of that province is that the soft woods, Douglas fir, cedar, 

 4c, do not contain any mineral matter and produce no ash when burnt. There is no 



•For a fuller account of this fertilizer, see report of this Division for 1898, p. 160. 



