Lime and Calcium Compounds 143 



Lime assists the decomposition of organic matter. 



Soils supplied with calcium carbonate or other basic- 

 compounds admit the normal decomposition of organic 

 matter which is the foundation of the formation of nitrate 

 nitrogen under conditions permitting the proper circula- 

 tion of air and moisture. Soils lacking calcium carbonate 

 or other basic-compounds permit the rapid accumulation 

 of free acids which poison the organisms responsible for 

 decomposition. 



Lime makes soil potash available. 



Many soils contain potash in large quantities in a form 

 not usable by plants. Soluble calcium compounds are of 

 prime importance in the conversion of some of this soil 

 potash into forms available for use by plants. The 

 effect of soluble calcium compounds in making the in- 

 soluble potassium compounds of the soil soluble may be 

 readily seen upon heavy clay soils or heavy limestone 

 soils where good crops of clover are produced annually 

 without the addition of potash salts. Though all of the 

 conditions influencing this change are unknown, yet it 

 is safe to say that it is primarily dependent upon the 

 nature of the potassium compounds existing in the soil. 



Lime makes soil phosphates available. 



Compounds containing phosphorus, especially phos- 

 phates of iron and aluminum, occur in many soils. These 

 particular compounds are very slowly soluble in soil water. 

 The change to a more soluble form is brought about more 

 readily in the presence of lime, especially when it is in the 

 form of carbonate or hydrate. It was thought for a long 

 time that use of lime where superphosphates are used in 



