THE SOIL AND ITS IMPROVEMENT 105 



11 lid put aside to settle. Carefully pour off the clear water into a 

 bottle having a good stopper. Test the water with litmus paper to 

 show it is ■' alkali." Save a supply for use in other exercises. 



When burned lime is slal^ed and spread upon soils, it is 

 readily dissolved by rain-water and carried down into the 

 lower soil. For this reason, lime should be placed on top of 

 the plowing and not plowed under. Its tendency is to move 

 downward with the soil water. 



The alkali test shown with the litmus paper shows the 

 power of lime water to " sweeten " sour soils. 



■ — 18. Fertilizer Samples. — Let several students who have extra 

 time write to a number of fertilizer companies, asking for samples 

 of both raw materials and mixed fertilizers for use in the school. 

 Some of these will come in nicely labelled glass bottles, while others 

 may be sent in envelopes or small packages. These should be trans- 

 ferred into bottles as uniform as the students of the school can find 

 about their homes. Suitable things to ask for are: Nitrate of soda, 

 sulfate of ammonia, high-grade tankage, low-grade tankage, dried 

 blood, fish scraps, phosphate rock (calletl "floats"), bone meal, acid 

 phosphate, steamed bone, basic slag, sulfate of potash, muriate of 

 potash, kainit, unleached ashes, hydrated lime, ground limestone, 

 gypsum, ground oyster shells. These samples should be preserved 

 for use in a number of exercises and for illustrative material in the 

 study of fertilizer problems. 



