760 



by each soil. The results of the first year's trial showed that soils 

 belonging to the same class and containing by analysis the same percent- 

 age of phosphoric acid, yielded widely varying amounts of phosphoric 

 acid to the plants growing upon them. Thus of two samples of clayey 

 soil, each of which contained by analysis 0.1 per cent of phosphoric acid 

 and which were used for summer wheat, No. I gave up 0.341 gram of 

 I)hosphoric acid to the crop, and 'Ho. II, 1.223 grams, the yield of grain 

 and straw each being more than three times as large on soil II as on 

 soil I. A large number of other soils also showed analogous differences. 

 The conclusion was that in soils containing like amounts of phosphoric 

 acid the amount of the acid which plants can utilize may be very different, 

 so that the mere estimation of the phosphoric acid in a soil by analysis 

 furnishes no indication of the supply which is available to plants. Tests 

 of the two soils just mentioned with ammonium citrate, "Petermanu's 

 solution," by the method for determining so-called reverted phosphoric 

 acid, revealed a decided difference between them with regard to the 

 phosphoric acid dissolved; thus, soil I yielded 0.032 per cent and soil II 

 0.05 per cent of phosphoric acid. In additional tests very weak solutions 

 of citric acid were used. The opinion is expressed that by the use of 

 this re agent, in connection with vegetation tests, it will be possible to 

 make an estimation of the phosphoric acid in a soil which is in a condi- 

 tion to be used by plants. 



Along with these tests other studies were carried on with regard to 

 the phosphoric acid in the harvested crop from different soils. The 

 results of these show that the soil richest in citrate soluble phosphoric 

 acid produced plants containing the largest amounts of phosphoric acid, 

 and that when nitrogenous fertilizers were applied to the soil, especially 

 in suflicient quantities to noticeably increase the yield, there was a 

 marked decrease in the phosphoric-acid content of the crop. 



In an investigation as to the content and solubility of the phosphoric 

 acid in the typical soils of the province, examinations were made of 

 over 400 samples of different soils, the results of which showed the sol- 

 ubility to vary widely in different soils. In sandy soil, for instance, 

 which of itself contained only a low percentage of jihosphoric acid, the 

 rate of solubility of the acid was found to be remarkably high ; thus in 

 some cases 95-100 per cent of the phosphoric acid present was dissolved 

 by citrate of ammonia solution, while the rate of solubility for clayey 

 soils is very much less. 



Regarding the percentage of phosphoric acid contained in soils, the 

 author gives the following general conclusions from his studies : Over 

 0.2 per cent of phosphoric acid is regarded as an unusually high con- 

 tent, occurring very rarely, 0.15-0.2 jjer cent as very high, 0.1-0.15 per 

 cent as high, 0.1 per cent as the normal content of a good sugar-beet 

 soil, 0.075 per cent as moderate, 0.05 per cent as low, and 0.025 per 

 cent as very low. 



