10 AGRICULTURE FOR COMMON SCHOOLS 



upon the proportions of sand, clay and silt in the soil. The 

 sandy loam, loam, and clay loam are the best soils for gen- 

 eral purposes. 



We must not forget that muck is called a soil, but it is not a 

 soil like those mentioned above, for it is made principally from 

 decayed stems and leaves. The sand and clay in it have been 

 carried in by the water which stood on, or ran over, the swamp 

 or lake before it was drained. If you were to take some dry 

 muck, weigh it and burn it and then weigh the ashes, you 

 would find that from two-thirds to three-fourths of its weight 

 had burned away. If you were to burn a loam soil, you 

 would lose hardly one-tenth of its weight, while there would 

 be still less loss from sandy and clayey soils, showing that 

 these soils do not have much organic matter in them. Muck 

 soils are sometimes called humus soils and the vegetable 

 matter in sands, loams and clays is called the humus. Real 

 humus is vegetable matter so completely decayed that one 

 cannot tell what it was like at first. It is very important that 

 soils have a good supply of humus, as we shall soon point out. 

 Most farmers are anxious to increase the amount of humus 

 in their soils, and try to do so by hauling manure on the fields 

 and by plowing under green crops like rye or clover, or the 

 stubble from any of the farm crops. 



Plant Food in the Soil. — Although the soil may be made 

 up of what appear to be particles of rock with a few pieces of 

 rotten roots and stems mixed with them, it contains the sub- 

 stances necessary to make plants grow and develop. There 

 are about thirteen substances which seem to be more or less 

 necessary for the plant, namely: hydrogen, oxygen, nitrogen, 

 phosphorus (phosphoric acid), potassium (potash), calcium 

 (lime), magnesium, iron, sulphur, sodium, silicon, and 



