42 MANURES FOR FRUIT TREES 



in. Irrigation should be practised as an insurance 

 against loss of fruit, etc. A pond fed by a wind- 

 mill would often save an orchard from destruction 

 or great injury, during a period of drought, and a 

 small engine could be used to drive an irrigating- 

 pump during such periods. 



The chief object of all cultivation is to maintain 

 an adequate supply of water and air in soils for the 

 proper growth of trees and other plants. Moisture 

 increases bacterial oxidation in the soil, and an 

 increase of oxidation means an increase of produc- 

 tiveness. This alone explains the value of a 

 proper supply of moisture. Water is the solvent 

 by which mineral matter of the soil is absorbed by 

 the roots and rootlets of trees. It must be borne 

 in mind that different trees require for their growth 

 sufficient quantities of different, but quite de- 

 finite, plant-foods, and that they take these chiefly 

 from the soil. It is absolutely necessary in a 

 proper system of cultivation of fruit-trees that the 

 plant- foods present in the soU must be in abund- 

 ance, and in an assimilable form — i.e., they must 

 be soluble in water (or water impregnated with 

 carbon dioxide) and the juices secreted by the 

 rootlets. 



In concluding the chapter, the fertility of a soil 

 can only be retained by the cultivator thoroughly 



