LIME 127 



frequently plowed under for humus. However, the prac- 

 tice is growing of feeding a part of these crops to the 

 stock and then using the manure on the land. In some 

 localities, a profit in fattening beef cattle can thus be 

 made as a by-product. Three fourths of the nitrogen and 

 phosphorus and one third of the organic matter of feeds 

 on the average live-stock farm is recovered in the manure. 



85. Lime, we have already said, is valuable mainly as an 

 indirect fertilizer. As such, it works in five ways : 



a. It liberates plant food that is held in insoluble com- 

 pounds in the soil, by combining with them into new com- 

 pounds which are soluble in the soil water. 



b. It hastens the decomposition of vegetable matter into 

 humus and makes available the fertility it contains. 



c. It aids the action of manure. The full benefit of 

 manure or other fertilizers will not be realized in soils 

 deficient in lime. 



d. It mellows clay soils, making them more granular, 

 friable, and loose. 



e. It " sweetens " the soil. This is the most important 

 use of lime. Decomposing vegetable matter leaves cer- 

 tain acids in the soil. These aid in making the soil sour, 

 so that needful bacteria cannot flourish. Lime corrects 

 this sourness, by combining with the acids into harmless 

 or helpful compounds. 



86. When Should Lime Be Used ? Litmus paper (to be 

 had at drug stores) shows whether the soil is sweet or 

 sour. Its use is a simple matter. Place a red and a blue 

 strip in a hole several inches below the surface. If the 

 blue paper reddens after remaining in contact with the 

 moist soil for an hour or less, lime is needed; if the red 

 paper turns blue, no lime is required. The presence of 

 plaintain and sorrel is commonly taken to indicate a sour 

 soil or a soil in need of lime. 



