298 YAED AND GARDEN 



ical substances and gases. The first is essen- 

 tial not onl}' as a source of food but as a food 

 solvent and a distributing agency of many es- 

 sential inorganic substances wliicli jjlant life 

 requires. The principal chemical substances 

 demanded by plants are potash, phosphorus 

 and lime; and the gases are nitrogen, oxygen, 

 carbon dioxide and hydrogen. Most of these 

 are present in the average soils of meadows, 

 but if the soil lacks them, they must be sup- 

 plied in greater or less quantities and in avail- 

 able form before sturdy plants of any sort can 

 be raised. This we do by applying fertilizers. 



GOOD GARDEN SOIL 



Fertilizers, however, will not put poor soil 

 into good mechanical condition. We might apply 

 hundreds of pounds of any or all of these ferti- 

 lizers to clay and still the plants supported by 

 the soil would not prosper. This would be due 

 to the fact that the food so supplied is not avail- 

 able. The mechanical condition of the soil 

 would prevent the proper assimilation of the 

 food and the plants would perish. To get soil, 

 therefore, into the best condition, we must first 

 of all cultivate it, work it and see to it that, 

 from the mechanical viewpoint, it does not pos- 



