. PRACTICAL AGRICULTURE. ^^17 



off without obstruction into the earth, and the upward 

 flow of water, after evaporation, should be unimpeded, 

 in order to supply the surface soil after a drouth. All 

 who have tried deep ploughing have become satisfied 

 that their fields are dryer for it in rainy weather, and 

 moister in dry weather. This accords perfectly with 

 the principles now explained. There may be soils 

 lying on so porous a subsoil that it would be well to 

 cultivate shallow. The farmer must look to this. In 

 extreme cases, he may find a subsoil so open and po- 

 rous that to stir it might be like knocking the bottom 

 out, to let his top-soil fall into the earth and be lost 

 among coarse pebbles. 



414. Whenever the soil is deep and the subsoil com- 

 pact, there can be no doubt that deep ploughing is 

 greatly beneficial. If plants can have ten inches of 

 loosened soil into which to thrust their roots for food, 

 they are like a herd of cattle in a pasture of ten acres ; 

 while if they have but five, they are like the same 

 herd confined to a five-acre lot. 



416. On all ordinary soils, ploughing should be at 

 least ten inches deep ; and then, if the soil below that 

 depth appears hard and compact, especially if there is 

 anything like a shell or crust, through which water 

 cannot pass freely, it should be stirred with the sub- 

 soil plough as much deeper. The water can then pass 

 up and down freely. All danger from excessive rains 

 is removed, because the water readily passes away 

 from the roots of plants ; and all danger from drouth 

 is removed, or nearly all, because the water will freely 

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