150 The Principles of Fruit-growing. 



pulverizing and fining the soil for the seed-bed, is 

 most efficient in furnishing an earth -mulch. The 

 spring -tooth harrow is in reality a cultivator, and 

 its action is similar to that of the cultivator. 

 When used as an instrument to conserve moisture, 

 the teeth should penetrate to the depth of about 

 three inches, and to produce the best effect the 

 ridges left by it should be leveled off by a smoother, 

 which can now be purchased as an attachment to 

 the harrow. The tillage of orchards by the harrow 

 is now practiced extensively, and nothing short of 

 irrigation will so nearly meet the demands of trees 

 for moisture, particularly upon the heavier soils. 



The Acme harrow is a most excellent implement 

 on soils which are comparatively free from stones 

 and rubbish. The plow -like action of its blades 

 serves to pulverize the soil, to spread the mulch 

 evenly, and it leaves a most excellent seed-bed. 



The cutaway or disc harrows may be either bene- 

 ficial or of absolute injury. If the discs are so set 

 that they cover but a portion of the surface with 

 the mulch, they leave a ridge exposed to the action 

 of the wind and sun, and the rate of evaporation 

 is greatly increased. The discs should be set at 

 such an angle that the whole surface shall be 

 stirred or covered. Their chief value lies in their 

 cutting and pulverizing action on clay soils, but as 

 conservers of moisture they are inferior to the Acme 

 or the spring -tooth. Soils which need the disc 

 harrow to pulverize them should generally be gone 

 over again with some shallower tool. 



