THE SOIL AND ITS IMPROVEMENT 103 



other 5 per ceut is made rnp of the ash or mineral matter 

 whicli they get from the soil. This 5 per ceiat is absolutely 

 necessary. Indeed, as this amount increases, the increase is 

 multiplied many fold by the part taken from the air. We 

 consider the portion taken from the air inexhaustible. This 

 illustrates the need of increasing the mineral food of plants 

 up to the greatest amount which they can use. 



14. Soils Retain Pleint-food. — Tie cloths to cover the large 

 ends of several lamp chimneys. Pack each chimney nearly full with 

 garden soil and stand each in a separate dish. Pour liquid manure 

 into one, ammonia water into a second, lime water into a third, and 

 water containing phosphoric acid into a fourth. After the water 

 passes through in each case, note such changes as can be observed. 

 The liquid manure will probably lose its characteristic color; the 

 ammonia water may lose its odor ; that which passes through should 

 be tested also with litmus paper. Test also the lime water with 

 litmus paper. Test the water from the fourth for phosphoric acid by 

 pouring lime water into it, as suggested in another exercise. If the 

 phosphoric acid passes through the soil of the chimney, it will cause 

 a white cloudy appearance when treated with lime water. The exer- 

 cise may be extended by the us^ of another chimney and a trial with 

 lye leached from wood ashes. 



Some kinds of soil are more retentive of plant-food than 

 others. Light sandy soils do not hold plant-food as well as 

 the heavy clay loams. Plants are able to get the food from 

 sandy soils more readily than from clay. That is, sand yields 

 to the plant more nearly all it has. 



rs. Rains Remedy Over-fertilizing. — In .two cans of good 

 garden soil plant beans or corn. The cans should have good drainage 

 in the bottom. When the plants are up a few inches, water one of 

 them with an excess of nitrate of soda or some other fertilizer. 

 Common salt solution may be used instead. When the plants begin 

 to show signs of wilting, stop this treatment. After one day, note 

 the difference in appearance between the plants in the two cans. One 

 should be healthy and vigorous, while the other is drooping and dying 

 because of the over-feeding or the strong salt solution. Before the 

 plants arc dead, water this can abundantly 'with pure water, using 

 rain-water if available. Let the surplus water drain through the 

 holes in the bottom of the can. 



