Soil Fertility 93 



pounds of potash to the 100; thus to get 200 pounds will 

 require double the quantity, or 400 pounds of sulfate of potash. 

 The pounds of the ingredients are as follows : 



Nitrate of soda (15%) . . . . . . . 134 Ib. 



Dried blood (6%) 334 Ib. 



Acid-phosphate (16%) 1000 Ib. 



Sulfate of potash (50%) 400 Ib. 



Total 1868 Ib. 



This is 132 pounds short of a ton. Any material such as 

 sand or ashes may be used as filler to make up the ton weight. 

 The same quantity of plant-food will, however, be placed on 

 the soil if only the 1868 pounds of material are used. 



LIME FOR SOIL IMPROVEMENT 



43. Uses of lime. Lime is a soil amendment and is useful 

 in many ways. It corrects the acidity of soils, is of aid in 

 rendering plant-food available, improves the physical condi- 

 tions of the soil, often makes it possible to grow some varieties 

 of legumes where they would not otherwise grow, and supplies 

 the plant-food element, calcium. 



Correcting soil acidity. The principal reason for using lime 

 is to correct the acidity, or sourness, of the soil. Lime is a 

 base and like all bases reacts chemically with acids to form 

 neutral salts. Any acid soil shows the good effects of appli- 

 cations of lime. 



The usual test for soil acidity is made by means of blue lit- 

 mus paper, a preparation that can be purchased in strips ready 

 for use at drug stores. Blue litmus turns red when exposed 

 to an acid ; consequently when placed in an acid soil the paper 

 becomes red. In making the test, a time should be chosen 

 when the soil is moist enough to work into a compact ball. 

 This does not mean that the soil should be wet enough to be 

 muddy. Make four balls of earth, break each of them into 

 two pieces, lay a piece of blue litmus paper on the broken 



