222 FUNCTIONS OF LIME IN INCREASING THE CROP 



it is of much advantage to possess a general idea of the func- 

 tions it performs in the soil or in the plant. We have stated, 

 in fact, that one of the objects we have in view, in our more 

 strictly scientific experiments, is to throw light upon the nature 

 of these functions, with a view to the ultimate profit of the 

 practical man. 



The functions which lime performs in the soil, though chiefly 

 chemical, are also in part mechanical. It consolidates light 

 sandy soils,* and generally opens such as are heavy and diffi- 

 cult to work ; but along with this mechanical, it always per- 

 forms important chemical functions. 



1. It directly neutralises such acid substances as already 

 exist in the soil ; and, being usually added in larger quantity 

 than is necessary for this purpose, it is ready to unite with new 

 acid compounds which may be formed. 



2. It promotes the decomposition of the organic and mineral 

 constituents of the soil, so as to prepare them for more readily 

 ministering to the wants of the plant. Among other benefits 

 which are supposed to result from this chemical action, are the 

 liberation of alkaline matter from the rocky fragments which 

 exist in the soil, and the production of nitrates from its organic 

 part. 



3. To the plant it supplies the lime so necessary to the pro- 

 duction of its several parts 5 and either as a carrier of other 

 kinds of food, or as a promoter of chemical changes within it, 

 lime, without doubt, performs other duties we are as yet unable 

 to specify. 



One common error in regard to the functions of lime the 

 experimenter should bear in mind. Lime will in many places 

 promote the growth of plants, but it will not anywhere serve 

 the purposes of other manure, or render ordinary manuring 

 unnecessary. Hence the reason why so much injury has in 



* This practice is very ancient. Thus Columella says, " Si tamen nullum 

 genus stercoris suppetet, ei multum proderit fecisse quod M. Columellam pa- 

 truum meum, doctissimum et diligentissimum agricolam, ssepe numero usurpasse 

 memorise repeto, ut sabulosis locis cretam ingeret, cretosis ac minium densis 

 sabulum ; atque ita non solum segetes laetas excitaret, verum etiam pulcher- 

 rinias vineas efficeret." De He Eusticd, lib. ii v cap. 16. 



