SOILS 127 



thoroughly dry, crush the soil in each pan. Note the hard- 

 ness of each soil. Write two sentences on the value of 

 manures or other organic matter to a soil. 



11. Observational study of the plant-food elements. Have 

 samples of some form of the ten plant-food elements de- 

 scribed in the chapter for observational work in these 

 studies. 



12. Testing soils for acidity. *ring in samples of soil 

 from the various homes of the community to test for acidity. 

 Cover a bit of blue litmus paper with moist soil, and after ten 

 minutes examine the litmus paper. If it has turned red, it 

 is an indication that the soil is acid. If hydrochloric acid be 

 poured upon the soil and it effervesces, it is an indication 

 that carbonates are present and that the soil does not need 

 limestone to correct the acidity. 



13. Soil drainage demonstration. There is on the market 

 now a very practical and simple piece of equipment called 

 the soil drainage apparatus which should be used in this 

 exercise to demonstrate the principles of drainage and to illus- 

 trate the process. Directions will not be given here, for they 

 accompany the apparatus when purchased. 



14. Simple soil tests for nitrogen. To tell accurately the 

 amount of nitrogen in soil requires elaborate equipment, but 

 the following method will answer for practical purposes and 

 does not require much apparatus. 



In a clean glass vessel which can be heated place two 

 tablespoonfuls of the soil to be tested. Add fifteen table- 

 spoonfuls of ten per cent caustic potash solution. In another 

 vessel add fifteen tablespoonfuls of water to two tablespoon- 

 fuls of soil. This is the control. Heat both samples to the 

 boiling point, and set them aside for five minutes. If at the 

 end of that time the solution which contains the caustic potash 

 is black and opaque, the soil is rich in nitrogen. If it is merely 

 dark and allows light to pass through it, the nitrogen content 



