THE VEGETABLE GARDEN 



humus is in great danger of becoming exhausted, 

 and the soil is then said to be " worn out." 



Humus is the black or brown material which 

 gives the dark colour to the top ten or twelve 

 inches of soil. Added to the soil, humus increases its 

 water-holding capacity, thereby insuring a more 

 constant soil moisture. It aids in the decomposi- 

 tion of the mineral matter by harbouring bacteria 

 which convert unavailable forms into a condition 

 in which it can be assimilated by plants. It fixes 

 the ammonia, which contains nitrogen, in the soil, 

 so that it is not leached out by rains, and it im- 

 proves the mechanical condition of the soil by keep- 

 ing it loose and free, permitting aeration. 



The natural supply of humus comes from the 

 decaying leaves and wood of the forest, but as soon 

 as the forests are removed and the land cultivated 

 this supply is cut off. It can be renewed, however, 

 by giving the land periodical dressings of stable 

 manure, green manure, or peat or swamp-muck. 

 These last two are not always available, and when 

 they are, it is doubtful if they can be economically 

 applied to land on account of the cost of hauling 

 and spreading. 



Stable manure is undoubtedly the best form in 

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