ARTIFICIAL MANURES. 357 



the land in a fair state of fertility for a very long time, and 

 here the use of mineral manures is less obvious than in other 

 cases. 



It is a fallacy, however, to suppose that these lands do not 

 need mineral manuring. By the system pursued, we are 

 simply drawing on the capital stock, and, sooner or later, we 

 shall touch bottom. It all looks fair enough now, but at 

 some future day we or our successors must pay the penalty 

 of our improvidence by finding that the land will no longer 

 produce good crops without the use of more purchased ma- 

 nure than can profitably be applied to them. 



The only safe rule (the only honest course, when we con- 

 sider the fact that we are only life-tenants of our farms, and 

 are in duty bound to leave them, unimpaired if not improved, 

 to those who are to come after us) is to bring back on to the 

 farm, every year, as much of the more valuable elements of 

 vegetable ashes as we have sold off from it, whether in meat 

 milk, grain, or hay. In this way only can we be sure that 

 our land and our crops will each year improve. 



The great deficiency of our older soils is in the items of 

 phosphoric acid and potash. (Lime is more often needed 

 as an agent for the development of matters already contained 

 in the soil than as a direct food for plants.) 



While ammonia has been classed among the non-essential 

 elements of manure, its action as a stimulant is so remark- 

 able that it is, commercially considered, the most valuable 

 of all. 



