THE SOIL AND ITS IMPROVEMENT 99 



food by exposing particles to new conditions of heat, light, 

 moisture and air. (3) To help prepare the soil as a seed bed. 

 (i) To deepen the water reservoir and make the moisture 

 conditions more perfect. (5) To loosen the soil and allow of 

 better shallow tillage. 



Depth of Plowing. — If soils be rich and black to a great 

 depth, the plowing may be as deep as desired. In shallow 

 soils, where the poor soil is close to the top, the depth of 

 plowing is limited. Very little, if any, poor soil should be 

 turned up at any one time of plowing. In such cases the depth 

 of the soil may be greatly increased by plowing deeper each 

 time. This increase should be Very gradual — one-half inch 

 or so at a time. If green manures or other forms of organic 

 matter be plowed under each time the lower soil will be 

 improved more readily and the plowing should become deeper 

 and deeper. In soils which are very sandy with loose porous 

 subsoils, there is much danger of plowing too deep, unless well- 

 rotted manure or other similar material be added each time. 



When the school garden is first being prepared the first 

 plowing should be shallow. If there be a sod to kill, the 

 second plowing, made perhaps a few months later, may be 

 crosswise of the first, tad made much deeper. 



Shallow Tillage. — In preparing a garden, the common 

 spike-toothed harrow, with adjustable or slanting teeth, is 

 most commonly used. For heavy soils a disk harrow is' very 

 helpful. The Acme harrow is a good instrument as a pul- 

 verizer for clods and sods. 



For cultivation between rows a fine-toothed cultivator is 

 used. ,For most garden purposes, either at school or home, 

 young people will find a one-horse cultivator, which is adjust- 

 able in width, a very desirable form. Wheel hoes are very 

 useful when horse power is not to be used. Tillage between 

 rows does not need to be deep for most crops, if the soil has 

 been properly prepared in advance. 



Bare Fallow. — In early spring, after the soil has been 



