36 HOW TO KEEP SOIL FERTILE 



they return to the soil the plant food they took from it in 

 growing. Almost all plant material, therefore, is good 

 to put on the ground to make it rich or fertile. Since 

 animals grow by eating plants, or by eating other animals 

 that grew by eating plants, most animal matter is also 

 good to fertilize the land. Manure, which is decaying 

 plant or animal matter from barnyards, stables, slaughter 

 houses, etc., is the most common material used to fertilize 

 the soil. 



Wood Ashes. Wood ashes contain the mineral mat- 

 ters that the trees from which the wood was obtained 

 took from the soil when they grew. Wood ashes, there- 

 fore, are valuable for making the soil fertile. If they 

 have not been leached, that is, if they have not been 

 exposed to water, they contain much potash and some 

 phosphoric acid, but no nitrogen. If they have been 

 leached, the potash has been mostly washed out. 



Commercial Fertilizers. In some parts of the world, 

 deposits are found that are rich in nitrogen, in phosphoric 

 acid, or in potash, and those materials are mined for fer- 

 tilizers of the soil. Some manufacturing establishments 

 have waste products that are useful as fertilizers. We 

 can, therefore, buy fertilizers in the market as we can buy 

 coal' or lime. But commercial fertilisers, as such fertiliz- 

 ers are called, are rarely so cheap or so good for the soil as 

 manure is, hence it is best for the farmer and gardener 

 to depend, as far as possible, on manure to enrich their 

 soil. 



Applying Fertilizers. Farm manures give best results 

 when applied frequently in small amounts, not over eight 

 tons to the acre. Heavy applications of manure on soils 



