THE IDEAL SOIL 31 



filled with water a long time after rain, the air would 

 be forced out and the roots of the crop growing on the 

 land might be smothered. The ideal soil must, therefore, 

 be well drained, so that its pores will not long remain 

 filled with water even in wet weather. This means that 

 the subsoil must permit the surplus water to pass through 

 it rather easily. 



Tiling. Soils over a subsoil containing too much clay 

 dry out slowly in spring, and after heavy rains. Such 

 soils may often be improved by draining, that is, by 

 providing ways for the surplus water to flow off. Ditches, 

 connecting with an outlet on lower ground, may be dug 

 through the land. Brick tubes called tiles are often 

 buried in such ditches, and the surplus water flows out 

 through these. (See Figure 16.) There are spaces between 

 the ends of the tiles, through which the water enters. 

 Sometimes brush or stones are used in place of tiles. Lands 

 thus drained are often among the best for farming. 



Plant Food in Soil. We learned from Lesson 4 that, 

 with the exception of carbon, the food of plants comes from 

 the soil, and that it is dissolved in the soil water. If the 

 soil does not contain food enough, the plants can not 

 grow well, even though they have everything else that 

 they need. The ideal soil must have sufficient plant food 

 in a form that can dissolve in water to supply the needs of 

 crops grown upon it. In the next three lessons, we shall 

 learn about supplying the soil with plant food. 



QUESTIONS AND EXERCISES. 



i. Why must the soil be porous in order to make plants 

 grow? 



