120 ELEMENTS OF AGRICULTURE 



LIME 



131. Functions of Lime. Lime is usually spoken of 

 as a soil amendment rather than as a plant-food, because 

 its chief value when added to the soil does not seem to 

 be as a plant-food. A deficiency of lime in the soil seems 

 to show in other ways before there is really a shortage 

 of lime as food. Lime helps to improve the physical con- 

 dition of some soils. It corrects acidity. It helps to liber- 

 ate other plant-foods. Perhaps its most important effect 

 is its influence on soil organisms. If there is not sufficient 

 lime in the soil, the fixation of atmospheric nitrogen 

 cannot go on properly, nor can the liberation of nitrogen 

 from the humus. The addition of lime to the soil so favors 

 the preparation of nitrogen food that its effect is often the 

 same as the addition of nitrogen. If a soil is deficient 

 in lime it is unwise to go on farming it until this deficiency 

 has been corrected. The other fertilizers or barnyard 

 manure cannot be used most economically if there is not 

 sufficient lime. On the other hand lime does not take the 

 place of these fertilizing materials. 



132. Relation of Crops to Lime. There is a very decided 

 difference in the lime requirements of different crops. 

 Alfalfa and clover need more lime than do any of the 

 other common farm crops. (See Fig. 97.) These may 

 show a benefit from the use of lime when timothy, corn 

 and wheat are not helped. Timothy may fail for lack of 

 lime where red-top thrives. Alfalfa, clover, lettuce, beets, 

 cantaloupes, onions, timothy are more sensitive to acid 

 conditions than are soy-beans, cowpeas, red-top and 

 watermelons. 



