Science progress. 



No. 3. May, 1894. Vol. I. 



THE DETERMINATION OF THE AVAILABLE 

 PLANT FOOD IN SOILS. 



THE chemical analysis of a soil, if carried out with 

 completeness and real accuracy, is a work demand- 

 ing much labour and skill. It has been frequently regarded 

 as a thankless task. Agricultural chemists of high standing 

 have proclaimed that such analyses were unreliable, because 

 it was improbable that the very small quantity of soil inves- 

 tigated by the chemist could fairly represent the enormous 

 quantity contained in a field. They further pointed out that 

 the results afforded no information upon the most important 

 questions. There was frequently nothing to show why one 

 held was fertile and another not. The quantities of plant 

 food shown by the analysis were generally, when calculated 

 on an acre of soil, extremely large ; yet experience had pro- 

 bably taught the farmer that the application of a small 

 quantity of a soluble phosphate,, of a potassium salt, or of a 

 nitrate, had the effect of considerably increasing the crop. 

 Some analysts, like Prof. Hilgard, have continued patiently 

 at work, notwithstanding hostile criticism, and by the accu- 

 mulation of experience have become able to interpret soil 

 analyses with considerable success, especially if relating 

 to a district already investigated. In such cases the 

 agricultural meaning of the analysis did not lie on its 

 surface, but was elucidated by bringing the analytical 



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