LIME AND MISCELLANEOUS FERTILIZERS 22 5 



one hundredth of a per cent to 20 per cent or 

 more. Soils which contain from 0.3 to 0.5 per cent, 

 as carbonate, are usually well supplied. The lime in 

 a soil takes an important part in soil fertility ; when 

 it is wanting, humic acid may be formed, nitrification 

 checked, and the soil particles will lack binding mate- 

 rial. Calcium carbonate is somewhat soluble in soil 

 water, due to the presence of carbon dioxide. Waters 

 are hard because of the presence of lime. The loss of 

 lime by leaching has caused many soils to become 

 unproductive. 



264. Different Kinds of Lime Fertilizers. By the 



term ' lime fertilizer ' is usually meant land plaster* 

 (CaSO 4 , 2 H 2 O). Occasionally quicklime (CaO) and 

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

 general, a lime fertilizer is one which supplies the ele- 

 ment calcium ; common usage, however, has restricted 

 the term to sulphate of lime. 



265. Action of Lime Fertilizers upon Soils. Lime 

 fertilizers act both chemically and physically. Chemi- 

 cally, lime unites with the organic matter to form 

 humate of lime and thus prevents the formation of 

 humic acid. It also 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. When soils are defi- 



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