SECTION XV. HOW TREES AND LEGUMI- 

 NOUS PLANTS IMPROVE THE SOIL 



IN a forest, year after year, the trees drop their leaves ; 

 the decayed leaves and roots make the soil very loose and 

 rich. When the trees are removed, the "new-ground" pro- 

 duces good crops that use the vegetable matter as food. 

 The crops are good on " new-ground " also, because 

 the humus in dry weather holds moisture like a sponge. 

 Drought, therefore, is not much felt by crops on land con- 

 taining much humus. When plowed, the dark, loose soil 

 crumbles readily, for the reason that vegetable matter in 

 the soil keeps the particles of clay from sticking together 

 and from turning up in great useless clods. 



Resting land not the quickest way to enrich it Farm- 

 ers have learned that even a crop of weeds adds vegetable 

 matter, and so they sometimes leave certain poor fields 

 uncultivated for a year or two to "rest" or improve. 

 Such improvement of the land is slow under any conditions. 



Making land fertile by growing certain crops. Differ- 

 ent plants are very unlike in the value of the vegetable 

 matter they add to the soil. Those that make the best 

 fertilizer are the plants rich in nitrogen. Look carefully 

 at the picture (Fig. 1 10) and notice how much more corn 

 grew on a square yard where vetch plants had grown the 

 year before. Twice as large a crop of oats, wheat, or hay has 



86 



