of nitrogen is saved, and danger of washing by 

 winter rains is lessened. 



4th. For humus, which is always necessary for 

 any form of crop. 



The Canadian field pea is the most popular plant 

 for this purpose. Beans and clover are also used. 

 Barley and other grains have not the same power to 

 absorb nitrogen from the air, and, unless turned un- 

 der green, dry out the soil and render it hard to 

 work. Barley is beneficial as far as its roots set free 

 unavailable forms of potash and phosphoric acid. 



The green manure wanted by orange growers is 

 one that will grow quickly, as California winters are 

 short and dry, and growers cannot afford to let the 

 ground rest undisturbed very long. 



HUMUS FERTILIZERS NECESSITY OF ORGANIC MATTER. 



Humus is decayed organic matter. It is necessary 

 for fertility, because all the nitrogen in soils comes 

 from either an animal or vegetable source. (Very 

 minute quantities are absorbed from the air as 

 ammonia and as nitrogen,) The nitrates come from 

 humus. They are water soluble and can be taken up 

 by the roots. Thus the plant gets its nitrogen. 



All fertile soils are rich in organic matter. The 

 exceeding richness of new lands is due to the humus 

 deposited by succeeding crops for generations. This 

 is true of both the high mesa and the valley land. It 

 is possible to use some chemical form of nitrogen and 



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