250 IMPROVEMENT OF THE SOIL 



CHAPTER VI. 



IMPROVEMENT OF THE SOIL. . 



The improvement of the soil is the great object of agricul- 

 tural chemistry. From a knowledge of the rocks and the 

 agencies which have been active in crumbling them into soil ; 

 from the physical and chemical character of soils, and, final- 

 ly, from the analysis in this country, we learn what they gene- 

 rally need to insure fertility. By an extensive analysis it ap- 

 pears that the earths exist in our soils in sufficient quantities, 

 with the exception perhaps of lime ; that the vegetable mat- 

 ters, alkalies and salts, are consumed by a continual course 

 of cropping, and must be constantly supplied. The mode of 

 improvement, then, relates principally to the application of 

 vegetable and animal matters, alkalies and saline compounds, 

 which latter includes carbonate of lime. 



The agents which we have considered in the first two 

 chapters, such as heat, light, affinity and electricity, depend 

 chiefly for their efficacy upon the character of the soil. Vege- 

 table substances, for example, render a sandy soil more re- 

 tentive of water, and of caloric, as well as more compact. 

 They render a clayey soil less retentive of water, but warmer 

 and more friable and permeable by the roots of plants. 



Carbonate of lime has been found an earthy ingredient of 

 nearly all rich soils ; and as our soils are nearly destitute of 

 it, they would generally be benefitted by its addition. Alka- 

 lies and saline compounds, such as potash, soda, ammonia, 

 nitre, common salt, etc. are, as we have seen, necessary for 

 the maturity of plants ; and, as they are exhausted by tillage, 

 they must be supplied, to keep up the fertility. There are 

 other modes of improvement, which pertain to the processes ~ 

 of tillage, which are all important, and which constitute the 

 principal features of the modern system of husbandry. We 



