The Relations of Lime to Soil Improvemext. 635 



is equivalent, therefore, to the application of potash and phosphate 

 fertilizers to the soil, not to mention the marked inllucnce on nitrates. 

 It may be remarked further that this is entirely legitimate, as the soil 

 store of food, while not to be wasted, is not to be hoarded; it is to be 

 used wisely. 



(b.) Lime corrects the lack of basicity in many soils. This lack 

 of basicity has often been termed acidity. That is not strictly true, as 

 there is not a positive soluble acidity. The 'great majority of soils give 

 solutions that are alkaline or neutral to phenolphthalein. But there 

 are silicate, iron and organic compounds, largely insoluble, which 

 have an avidity for lime, the satisfaction of which contributes largely 

 to productiveness. 



(c.) It is now well established that there may be various 

 types of toxic substances in the soil, largely of an organic character. 

 It has also been shown that some of these are rendered less injurious 

 by an abundance of lime in the solution. 



(d.) Organic matter in the form of humus is a very important 

 constituent in the soil. It represents an advanced stage in one type 

 of decay. This type, while largely biological, is generally identified 

 with a good supply of lime, and in the absence of lime the organic 

 matter may disappear without the production of the humus substance. 

 Further, the acid humic substance is very soluble and hence readily 

 lost by leaching. The brown liquid from manure heaps and swamp 

 land which is so characteristic of many southern streams is due to this 

 soluble humus. A base, such as lime, forms with it less a soluble com- 

 pound so that the humus is fixed and retained. The excellent supply 

 and condition of humus in the majority of the soils of the Northwest- 

 ern states and of the Houston or black prairie soils of the Gulf states 

 are largely traceable to their high percentage of lime. Thus we see 

 that lime is essential to a proper utilization of raw organic matter. 



(3.) Physical effects. (a.) The most marked physical effect of 

 lime is seen on clay soil. Lime flocculates the finest particles and pro- 

 motes a granular structure. This is exceedingly important, because 

 the physical properties of the soil, particularly its porosity, which is 

 determined by the fineness of the particles and their arrangement, 

 determine the retention and movement of water, circulation of air. and 

 temperature, through which the food supply is made available. ]*^xper- 

 iments show a very pronounced amelioration of puddled clay soil by 

 the use of lime. This effect was in fact the earliest object of liming. 



