198 SOILS AND FERTILIZERS 



247. Different Kinds of Lime Fertilizers. — By the 



term 'lime fertilizer' is usually meant land plaster 

 (CaSO .2H 2 0). Occasionally quicklime (CaO) and 

 slaked lime (Ca(OH) ) are used on exceedingly sour 

 land. In general a lime fertilizer is one which sup- 

 plies the element calcium ; common usage, however, 

 has restricted the term to sulphate of lime. 



248. 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 prevent 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 prevents losses, as the 

 washing away of fine earth. 



249. 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. In fact nitrogen, phosphoric acid, and potash 

 may all be present in liberal amounts, but in the 

 absence of lime poor results will be obtained. Ex- 

 periments at the Rhode Island Experiment Station 

 indicate that there are large areas of acid soils in the 

 Eastern States which are much improved when treated 

 with air-slaked lime. 67 There is a great difference in 

 the power of plants to live in acid soils. Agricultural 

 plants are particularly sensitive, while many weeds 



