LIME FERTILIZERS 189 



slaked lime (Ca [OH] 2 ) are used on very sour land. In 

 general a lime fertilizer is one which supplies the 

 element calcium ; common usage, however, has re- 

 stricted the term to sulphate of lime. 



250. Action of Lime Fertilizers upon Soils. Lime 

 fertilizers act both chemically and physically. Chem- 

 ically, lime unites with the organic matter to form 

 humate of lime and thus prevents the formation of 

 humic acid. It aids in nitrification and" acts upon 

 the soil, liberating potassium and other elements of 

 plant food. Physically, lime improves capillarity, 

 precipitates clay when suspended in water, and pre- 

 vents losses, as the washing away of fine earth. 



251 . Action of Lime upon Organic Matter. When 

 soils are deficient in lime, an acid condition may de- 

 velop to such an extent as to be injurious to vegeta- 

 tion. Nitrogen, phosphoric acid, and potash may all 

 be present in liberal amounts, but in the absence of 

 lime poor results will be obtained. Experiments by 

 Wheeler at the Rhode Island Experiment Station in- 

 dicate that there are large areas of acid soils in the 

 Eastern States which are much improved when treat- 

 ed with air-slaked lime. 68 There is great difference 

 in the power of plants to live in acid soils. Some 

 agricultural crops as legumes are particularly sensi- 

 tive, while many weeds have such strong power of 

 endurance that they are able to thrive in the presence 

 of acids. Weeds frequently reflect the character 

 of a soil as to acidity, in the same way that an "alkali" 

 soil is indicated by the plants produced. 



