SOIL MOISTURE 65 



surface of the soil will break the connection of the spaces or 

 pores with each other. If this capillary connection is broken 

 near the surface the moisture will be checked in its upward 

 movement and be held near the roots. 



The covering of fine soil produced by a harrow or culti- 

 vator is called a dust mulch or fine soil mulch (Figs. 36a and 6). 

 The chief purpose of the dust mulch is to save moisture. As 

 growing plants use a very large amount of water, it is wise 

 for the farmer to keep a fine soil mulch on the fields all the 



FIG. 36o A ten-shovel sulky cultivator. This form of machine leaves a fine 

 oil surface which helps to save moisture. 



FIG. 366. A one-horse walking cultivator with many small shovels and a smooth 

 rake behind. The fine soil mulch produced is the best means of preventing evapora- 

 tion of the moisture. 



growing season. If the tubes and pores through which the 

 water passes are undisturbed the water will escape rapidly 

 into the air. If, on the other hand, these tubes are broken 

 by tillage, evaporation is checked. 



EXERCISE. Effect of Mulch. When the ground is dry 

 place an old cloth or carpet or a bunch of hay on the ground. 

 In a day or so the ground under this mulch will become 

 moist by drawing water up from beneath, while the ground 

 around the mulch may remain quite dry. A covering of 



