Supplying Soil Needs 187 



In order to assure himself of a supply of manure, Why mixed 

 every farmer should keep some livestock. If he does ^t^ 9 IS 

 so he makes a double profit, a profit on feeding the mended 

 grain that he raises and a profit on the manure that is 

 put back into the soil. Grain farming without keeping 

 a reasonable number of farm animals is called " soil 

 robbing " ; the supply of humus and the other elements 

 of fertility grows less ; the soft becomes poorer, and so 

 does the farmer. That is why those who best under- 

 stand the science of agriculture recommend mixed farm- 

 ing the raising of livestock along with properly rotated 

 grain crops. 



Experiments and Observations 



1 . Visit a fertilizer store and copy the labels on the bags show- 

 ing the composition of the fertilizers. Bring these copies to class 

 for discussion. 



2. Plant two rows of radishes, sprinkling a little sodium nitrate 

 or a little complete fertilizer in one row with the seeds. Avoid 

 using too much fertilizer, as this would kill the plants. 



3. Into a tablespoonful or more of dilute sulfuric acid pour 

 household ammonia until the acid is neutralized and the mixture 

 smells of ammonia. Boil away the water. A white solid will 

 be left. This is sulfate of ammonia. 



4. Soak wood ashes in a bucket for several days. Pour off 

 the clear liquid and boil it away to get the dissolved potash. 



5. Thoroughly dry two balls of wet clay, in one of which a little 

 lime is mixed. Which one bakes the harder in the sun? 



6. Test the beneficial effects of manure by raising the same 

 kind of crop on each of two small garden plots. Fertilize only 

 one of the plots, by digging manure into the soil. 



7. Partly fill a box with manure and pour water over it occa- 

 sionally. Catch the drippings in a bucket, and notice the color. 

 Florists use such liquid fertilizer on ferns. What does this experi- 

 ment show as to the effect of rain on unprotected manure heaps ? 



