591.131 3 12 



631. 



Ill 



A New Method in Soil-Analysis. 



IT is proposed in the present paper to give a brief account of an 

 important memoir on soil-analysis, recently contributed by Dr. 

 Bernard Dyer to the Chemical Society, which would otherwise be 

 likely to escape the notice of readers of Natural Science. As every- 

 body knows, there are certain chemical elements, such as nitrogen, 

 phosphorus, potash, calcium, and iron, whose presence in the soil is an 

 essential condition of plant-life ; and, naturally, one of the first results 

 of modern chemistry was an analytical examination of the various 

 soils in order to determine in what proportions these constituents of 

 plant-food were present, and, on the other hand, what soils — whether 

 owing to exhaustion by long-continued harvesting, or to natural 

 poorness and infertility — required the addition of manures. 



At first, no doubt, the problem appeared delightfully simple and 

 straightforward. With the methods of modern analysis it was easy 

 to make very accurate examinations of the soil ; and if phosphoric acid, 

 for instance, were found in minute quantities only, clearly that soil would 

 require dressing with phosphatic manures ; while if, say, *2o per cent, 

 of phosphoric acid were present, it would stand to reason that the soil 

 was in a fertile condition and required no application of manures. 

 Unfortunately, however, like many other things that " stand to reason," 

 this simple inference was often sadly at fault. For instance, as 

 Dr. Dyer points out, it is very usual to find about '15 per cent, of 

 phosphoric acid in an average English agricultural soil ; and this 

 represents about two tons of phosphoric acid an acre distributed in 

 the upper nine inches of soil alone, to say nothing of the supplies in the 

 sub-soil, which, of course, are also utilised by the plants : yet, strange 

 though it may appear, the addition of a few hundredweights of phos- 

 phatic manure to this soil, which contains already as much phosphoric 

 acid as ten tons of bone-dust or seventeen tons of superphosphate, will 

 result in a full crop of turneps instead of a bad one. 



In the light of such experience it was soon recognised that the 

 determination of the total phosphoric acid present in the soil, and 

 soluble in mineral acids, was of almost no value as an index to the 

 fertility ; since it was clear that only a small unknown proportion of 

 that present was in a condition available for the use of plants ; and 

 that proportion, until recently, we had no means of determining, 



