8 The Value of Soil Analyses to the Farmer. 



soils can be established, if the results of a particular analysis 

 are to be interpreted for the service of the farmer. To say a 

 place is 200 feet above sea level tells nothing as to whether it 

 is situated in a valley or on a hill unless the general level of 

 the surrounding country is also known. 



Another line of attack has recently been attempted ; the soil 

 can be put under standard conditions of moisture and warmth 

 in the laboratory, and the rate determined at which it under- 

 goes chemical change by reason of the bacteria it contains. 

 The fei'tility of a soil largely depends upon the rapidity with 

 which its organic matter is decomposed by bacteria and its 

 nitrogen compounds transformed into soluble ammonia and 

 nitrates, the forms taken up by plants. Various methods 

 for doing this have been worked out ; the carbon dioxide 

 produced may be determined as a measure of total bacterial 

 activity, or the rate at which ammonia and nitrates are 

 formed from day to day may be ascertained. These methods 

 certainly discriminate between fertile and poor soils, but they 

 do not as yet throw any light on the causes of the differences 

 revealed, and they have to be applied to a large number of 

 known soils before their value in forming an opinion on an 

 unknown soil can be assessed. 



There still remains the difficult cases of abnormal soils 

 which behave entirely differently from their neighbours, 

 generally worse in the cases submitted to the analyst. Some- 

 times the solution is simple, as for example in several cases in 

 my own experience, where the bad field is one that has never 

 been limed or has escaped the chalkings by which the sur- 

 rounding fields have been made fit for arable cultivation at 

 some date so remote that all remembrance of the treatment has 

 been forgotten. But more commonly the factor involved is 

 one that eludes our still imperfect methods of analysis. For 

 example, in Romney Marsh one may find fields side by side that 

 have both been in grass from time immemorial, but one will 

 fatten six to eight sheep to the acre during the summer, whereas 

 the other, however lightly stocked, will only keep its occupants 

 gi'owing. Dr. Russell and I spent much time over this problem, 

 dealing with three distinct pairs of such soils differing widely 

 from one another in type. But the good soil always resembled 

 the bad soil alongside, in both physical and chemical constitu- 

 tion. Continuous observations of the amount of water in the 

 soil, the distance to underground water, which w^as close to 

 the surface, the temperature, and other factors failed to reveal 

 any significant differences. The good soil certainly was more 

 active than the bad one, producing nitrates and ammonia 

 more rapidly, and there were certain small constant differences 

 between the two soils, but we were unable to detect the causal 



