i37S ON THE CULTIVATION 



tlu'ee times tlie amount of oats, and twice of lye-grass, tlie 

 very crops which are made to form part of the rotation along' 

 w^it'h it. 1 



Besides, potash is one of those substances which has a 

 strong- affinity for water, and is, on that account, very sohdjle 

 in every state of combination in which it is found in the 

 soil; hence its great liability, when the land is under culti- 

 vation, to be carried off' by rain. This observation, however, 

 applies more to the rain which falls in inland situations, or 

 to those localities which are screened from the sea by some 

 high mountain range ; for there is g'ood evidence to show 

 that portions of the various saline substances contained in 

 sea-water, and which contribute so much to the fertility of 

 the soil, are often carried to considerable distances from the 

 shore. "^ We may further observe, that it is owing- to the 

 still g'reater amoimt which the different green crops require 

 of inorg-anic as well as of organic food, that a larg-e applica- 

 tion of manures is found to be necessary for their growth, in 

 Avhich case those sidjstances cannot be said to be abstracted 

 from the soil. 



Althoug-h these remarks are made more particularly in 

 reference to potash, as the substance which, with the excep- 

 tion of lime, enters more largely into the composition of clover 

 than any other, and one which is more apt to be washed from 

 the portions of the soil which is subjected to frequent culti- 

 vation, still they are applicable to other inorganic consti- 

 tuents, though many of them are less soluble, and exist often 

 in much larger proportions than jiotash. This view of the 

 case helps to explain why the red clover crop is less abundant 

 on land which has been frequently cultivated, and why its 

 faihu-e is more perceptible on inland situations, than in those 

 more exposed to the sea. But there are often causes of 

 failure on soils which cannot be said to be deficient in any of 

 the substances essential to the growth of this crop. 



In the spring of 1841 we commenced a series of experi- 



' Gypsum has been strongly recommended by Sir Humphry Davy, and 

 other writers on agriculture, as a valuable manure for red clover ; but we 

 have found that coal, peat, and wood ashes — particularly the ashes of ash- 

 wood — are much more efficacious. This is chiefly to be attributed to the 

 potash which they contain. 



^ Liebig's Agricultural Chemistry, pp. 110, 138. And we believe that 

 Dr. Madden, when at Penicuick, had satisfactorily proved, by a series of 

 ob.-ervations there recently made, that the rain which falls between the sea 

 and the Pentland hills contains more saline substances than the rain which 

 falls bevond that ranae. 



