SOILS AND FERTILIZERS. 399 



and let us suppose the deficit not jet made up, the crop again shows 

 improvement. Wow, phosphoric acid abounds in the soil, though the 

 deficiency in nitrogen and potash has become steadily greater; so, 

 when the customary bone meal is applied, the crop falls back, because 

 the plants are starving for potash and nitrogen. They are like scurvy- 

 smitten sailors, but many thoughtless farmers would attribute the 

 decline to the maker of the bone meal, and say that its quality was 

 not so high as formerly — an opinion similar to that of a sea captain 

 who would ascribe to the poor quality of salt beef an outbreak of 

 scurvy on his vessel. 



As crops of any description extract potash, nitrogen, and phos- 

 phoric acid from soils, the question how they are to be replaced is an 

 important matter, and its answer may be most readily found by study- 

 ing Nature's methods. In parts of the Old World there are fields 

 that are fertile in the extreme after thousands of years of tillage, and 

 it is apparent that mere cultivation does not prove injurious. The 

 tropical forests have something growing wherever a plant can find 

 foothold — a population in which the struggle for food is secondary 

 to that for light and air, and yet the soil supporting this vegetation 

 is marvelously rich. Every leaf that falls remains where it fell until 

 in the warm, moist, half-lighted forest it becomes a little heap of 

 mold. The bacteria of decomposition require warmth and moisture 

 for their life; light is deleterious to them, but they thrive in the 

 dense shade of the jungle. The tangled web of roots, weeds, and 

 vines retains the rainfall, retarding evaporation, and preventing both 

 droughts and freshets. Receiving dead and broken leaves, boughs, 

 and other vegetable products, and spared the washing of violent. tor- 

 rents, the forest is inestimably fertile. 



On a smaller scale this goes on universally. The annual weeds, 

 deciduous leaves, and such matter, fall prey to molds and bacteria, 

 by which they are made soluble. Snows and rains bear the products 

 into the soil, and there other bacteria, clustering around the roots, 

 form the acids needed to complete solution. Every one knows that 

 " well-rotted " manure is better than that which is fresh, and many 

 wonder at this, but the reason is apparent. In feeding delicate pa- 

 tients, physicians often prescribe predigested foods or the digestive 

 ferments to aid enfeebled assimilation; and similarly the manures 

 that have been thoroughly acted on by bacteria, or containing those 

 capable of producing the matters that plants need, are of most value 

 for nourishing vegetation. 



In producing an article of any sort, the cheapness and ease with 

 which it can be made is largely dependent on the shape in which the 

 raw material reaches the factory. If a foundry can procure iron that 

 needs only to be melted and cast, the owner can fill his orders more 



