56 ELEMENTARY AGRICULTURE 



into a tumbler of water. Into another tumbler put a 

 lump of salt or a piece of rock salt about the same 

 size. Which dissolves the sooner ? Stir both and note 

 the effect of stirring. Does stirring hasten solution? 

 Now put the same amount of fine salt in each of two 

 glasses. Stir one, but do not disturb the other. 



The Effect of Stirring Soil. You have noticed, in 

 the above experiments, that lumpy salt dissolves much 

 more slowly than fine salt, and that stirring always 

 hastens solution. It is just so with plant foods con- 

 tained in the soil. Lumpy soil holds the plant foods 

 so that the plant cannot get them, and cultivation 

 has the same effect upon them that stirring has upon 

 the salt in the water. It causes them to dissolve or in 

 some way makes them accessible. The plant cannot 

 use these foods until they are in the right condition, so 

 that excellent preparation of the soil before planting, 

 and constant cultivation of it after planting, both tend 

 to increase the supply of plant food as well as to 

 hasten the growth of plants. 



Deep Cultivation Best. The depth to which soils 

 should be cultivated depends in a large degree upon 

 the depth to which the plant roots will penetrate. The 

 grains are shallow-rooted and do not need so deep 

 cultivation as do corn and root crops. The farmer is 

 not likely to plow too deep for any crop, however. 

 Deep plowing brings to the surface plant foods that 

 have never been reached by shallow cultivation, and it 

 pulverizes the soil so that the roots can penetrate it to 

 a great depth and have more soil to feed upon. 



