NATURAL SOURCES OF FERTILITY. 145 



and only then, does this soil contain plant-food, or possess the 

 capacity to nourish and grow plants to perfection. 



It is so with the soil of our fields. Incapable of producing 

 plants when brought out of chaos, great powers, forces and 

 principles were started into activity to make the necessary 

 change. Silently and unseen, but surely and incessantly, are 

 these agents accomplishing their appointed work. The frost of 

 winter, with its crushing, disintegrating power, is reducing the 

 rock-particles to powder to prepare them for the more efficient 

 action of its co-working agents. The heat of summer is de- 

 composing the organic ingredients, and giving to the soil 

 gases and acids for their secondary work. The air is perme- 

 ating it with its oxygen to form acids, and corrode and take to 

 pieces its metallic elements ; with its carbonic acid and am- 

 monia to unite with other acids or alkalies in the soil, forming 

 new and needed compounds. The moisture of the atmosphere 

 is condensed to rain, and, descending to the earth, carries into 

 the soil its gases for plant-food, and dissolves the material pre- 

 pared by the other agencies. Year after year, in an unceasing 

 round, these influences work on, fitting the crude earth for plant- 

 food ; and when under the hand of nature alone, laying up great 

 accumulations of it for future use. 



Nature's processes are enriching, but never exhausting ; and 

 the plants which nature causes to spring up are simply agents 

 in the good work. They send their rootlets through the soil, 

 gathering its mineral elements when made solvent, and storing 

 them up within themselves ; their leaves into the fertilizing at- 

 mosphere, and gathering from it its carbonic acid and nitrogen ; 

 and when all are gathered, and the functions of plant-life 

 cease, carry back all they took from the soil, with the addition 

 of what they derived from the air. Crop after crop, in annual 

 succession, repeats the process. When decomposition takes 

 place, the carbonaceous matter seizes and holds securely all 

 these materials from being washed out by the falling rains, or 

 carried away by the searching air, until the plant shall seize 

 and appropriate them to itself. Thus plant-food, under the 

 hand of nature, is produced and stored up ; produced faster 

 than is needed, and laid away for a future emergency. That 

 emergency comes when the soil passes under the hand of man, 

 and is made to produce food-yielding plants, which are removed 

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