IMPROVING THE SOIL. 47 



CONCLUSIONS : 



1. All of our soils were once fresh, unworked, virgin soil. In 

 many cases worn-out soils were once very rich ; they have been 

 made poor by over-cropping and little fertilizing. 



2. Many soils have but a small amount of mineral food in a 

 soluble or available form. 



3. Bare fallowing is for the purpose of working over the 

 hard, rocky, insoluble portion of the soil into soluble form. 

 This is done by frequent plowing and harrowing, thereby letting 

 the air in. Weeds also are sprouted and afterwards killed. 



4. Green-manuring has the same effect, but prevents loss of 

 food through drainage, and increases the humus of the soil. 



5. The three substances that are most deficient in the soil 

 are nitrogen compounds, phosphates, and potash. 



6. The value of a fertilizer consists not only in the amount 

 of these three substances, but also in their state of solubility. 



7. Nitrogen is found in nitrate of soda, sulphate of ammonia, 

 dried blood, guano, fish refuse, etc.; phosphates in bone manures 

 and rock phosphates ; potash in wood ashes and potash salts. 



8. Barnyard manure is a general fertilizer supplying all three 

 constituents. Its value consists largely in its humus. 



9. Quicklime, land plaster or gypsum, and salt are valuable 

 as fertilizers, not because they contain plant food, but because 

 they act upon the soil, setting free insoluble plant food. 



10. Draining, tilling, and airing the soil are necessary for 

 the nitrification of humus, or the making of nitrates in the soil. 



SUGGESTIVE : 



Moisture is necessary for the speedy decomposition of green crops when 

 plowed under. Might a soil be injured for a while by turning under a 

 crop of rye during a dry time ? 



We have seen that fertilizers must be dissolved before they can be taken 

 up by the plant. What is the effect of pouring water over a pile of manure ? 



Does not this leaching lessen the value of the manure ? Is it not desir- 

 able, therefore, to prevent this loss by providing a cover for the manure 

 pile? This liquid fertilizer is very valuable. 



