COMMERCIAL FERTILIZERS ill 



138. What soils need lime. Land that has been heavily 

 cropped for a long time is likely to need lime. The soils of 

 regions of heavy rainfall are more apt to be deficient in lime 

 than are those of drier regions, because of the leaching effect of 

 the rains. Soils upon which legumes thrive, especially alfalfa or 

 red clover, are certain to have plenty of lime. On the other hand, 

 land that produces redtop, sorrel, or dock, and on which leg- 

 umes do not thrive, is very apt to need lime or drainage, or both. 



FIG. 47. Effect of liming alfalfa soils. (Photograph from Rhode Island 

 Experiment Station) 



139. The kinds of lime to use. Many of the fertilizers in 

 common use, as wood ashes, phosphate rock, basic slag, and 

 marl, contain a considerable quantity of lime ; but most of the 

 agricultural lime is derived from limestone and is applied in the 

 form of quicklime, freshly burned limestone, or in a raw state 

 after having been finely ground (Fig. 47). Quicklime has almost 

 double the sweetening power of ground limestone, 56 pounds 

 of the former being equal to 100 pounds of the latter. Quick- 

 lime also hastens the destruction of the organic matter in the 

 soil, and by this means, as well as in its action upon the soil 



