Natural Fertility of the Soil 9 



absorptive and retentive power of soils, it has been shown 

 that if they are well supplied with vegetable matter and 

 carefully cultivated, they retain and hold the plant-food 

 constituents in a much greater degree than if devoid of 

 humus and improperly managed, and also that the drain- 

 age water from soils upon which crops are growing sel- 

 dom contains more than the merest trace of nitrates. 

 The loss of nitrogen through the operation of the forces 

 of nature may, therefore, be reduced by the careful 

 management of the soil. 



Importance of careful culture. 



The presence of suitable amounts of vegetable matter, 

 and good cultivation, are conditions that are within the 

 power of all farmers to provide, though it is sometimes 

 impracticable to keep the land continuously covered with 

 a crop ; and sometimes it is thought that the loss incurred 

 through leaching because of the absence of a growing crop 

 is more than balanced by the gain in other directions. 

 For example, though losses of nitrates may occur, the gain 

 in availability of the mineral constituents, phosphoric 

 acid and potash, with the accompanying improvement 

 in texture, due to the exposure of the soil to atmospheric 

 influence, more than balances these losses, particularly 

 during the winter, with its wide changes of temperature. 



Loss of nitrogen by drainage. 



It has been shown by carefully conducted experiments, 

 both in this and other countries, that in a season of aver- 

 age rainfall the drainage waters carry away from one 

 acre, from uncropped soils only fairly rich in plant- 

 food, as much as 37 pounds of nitrogen a year, while 

 when continually cropped the drainage waters from the 



