FEKTILIZERS. 97 



In some cases it contains a large quantity of ordinary 

 soil, or other comparatively worthless matter. Some 

 samples yield three or four times as much nitrogen as 

 others. Before much expense is incurred in procuring 

 muck from any particular bed, some idea of its value 

 should be obtained, either by chemical analysis or some 

 other experiment. 



Some idea may be obtained of the proportional amount 

 of worthless sand, or other mineral matter which the 

 muck contains, by placing a small quantity in a tube or 

 glass of water, shaking the glass thoroughly, and, after 

 allowing it to stand for some time, noting the quantity of 

 mineral substances which settle to the bottom. 



QUESTIONS. 



What is fertile soil ? Name the elements necessary to make soil fer- 

 tile ? Would a soil containing no sulphur be fertile ? AA^ould scraps 

 of leather, which are largely composed of nitrogen, add to the pres- 

 ent fertility of soil ? In what way is the fertility of the soil naturally 

 maintained? What is the effect of raising crops? 



AVhat processes are going on in the soil ? Do rocks furnish food for 

 plants ? What effect has cold weather upon the chemical processes 

 in the soil ? What is the effect of the atmosphere ? Plow do fer- 

 tilizers aid the chemical action ? What becomes of the fertilizing 

 substances formed in the soil? Why is it more important that 

 loose soil should be always occupied with vegetation than clayey 

 or mucky soil? 



What elements are most generally lacking as soil becomes impover- 

 ished ? Why is nitrogen expensive as a fertilizer ? In what forms 

 does it generally become food for plants ? Where is nitric acid 

 found, and how is it produced ? How is ammonia formed ? Where 

 is it to be found in nature ? In what way does the farmer add to 

 the natural supply of nitric acid and ammonia? 



What is meant by nitrification ? How is the process brought about ? 

 What conditions are necessary? Why is the supply of nitrogen 

 smaller in the early spring than in summer ? 

 Wins. Agk. — 7 



