MANURES. 



165 



comes in contact, and causing the formation of 

 carbonic acid, ammonia, and other compounds; 

 hence it is of great utility in fertilizing peats, and 

 all soils abounding in roots and inert vegetable 

 matter, by decomposing the vegetable fibre, and 

 reducing it to a more soluble state. 



Respecting the chemical action of lime in the 

 soil, much uncertainty prevails. There is no 

 doubt that lime, by decomposing vegetable 

 matter, contributes to the food of plants by 

 supplying them with carbonic acid, ammonia, &c. 

 Liebig ascribes the beneficial action of lime 

 chiefly to its affording a supply of potash and 

 soda, by decomposing minerals which contain 

 these substances. Lime is itself a necessary 

 element of the food of plants, and its application 

 may in some cases prove beneficial by furnishing 

 plants with an indispensable element of their 

 food; but that would only be in soils deficient 

 in lime. We may therefore conclude, that lime 

 acts more by bringing other substances into a 

 proper condition for being absorbed by the roots 

 of plants, than by affording nourishment of itself. 

 Some soils, especially such as are peaty, become 

 what is called acid or sour, owing to the presence 

 of vegetable acids ; on such soils lime acts as a 

 corrective, by uniting with and neutralizing its 

 evil effects. 



Lime in its hot or caustic state is applied with 

 great advantage to soils containing an excess of 

 inert vegetable matter, such as peaty soils and 

 recently broken up grass-land. The roots, fibres, 

 &c, in these cases would long remain in the soil 

 in an undecomposed state, and one in which they 

 could yield no nourishment to plants; but lime, 

 by decomposing and rendering soluble this vege- 

 table matter, reduces it to a state in which it 

 can be taken up by the roots of plants and 

 assimilated. 



The addition of lime to clay soils is not only 

 followed by the usual chemical effects produced 

 by the application of lime, but the texture of 

 the soil is also improved. The effects of lime on 

 clays, however, greatly depend on the amount 

 of organic matter which these contain. If the 

 soil is deficient in this respect, lime will chiefly 

 prove advantageous by liberating the alkalies 

 potash and soda. 



The quantity of lime that should be applied to 

 an acre of ground varies from 30 to 200 bushels. 

 Where the soil contains much vegetable matter, 

 as in the case of grass -land which has been 

 recently broken up, the larger quantity may be 

 advantageously employed for a first liming. Clay 

 soils require more than light loams or sands; 

 and whenever there is only a small amount of 



vegetable matter in the soil, lime should be used 

 only in small quantities, otherwise exhaustion 

 will be the result. 



In all cases, it should be remembered that lime 

 will not supply the place of organic manure, and 

 that it merely renders this available for the 

 nourishment of plants. Where the. ground has 

 been long manured with farmyard manure, as an 

 old kitchen-garden, for instance, the use of small 

 doses of lime proves very advantageous in hasten- 

 ing the decomposition of the vegetable matter. 



In applying lime to the soil, it should be used 

 as a top-dressing, or forked in so as to mix it well 

 with the soil. From the tendency which lime 

 has of sinking deeper and deeper into the earth, 

 it frequently accumulates in the subsoil. If the 

 nature of the latter will permit, the lime may be 

 recovered by trenching it up, and this, in most 

 cases, is preferable to liming afresh. 



Lime is very advantageously employed in 

 forming composts with ditch -scourings, earth, 

 weeds, &c, as it hastens the decomposition of 

 the vegetable matter, liberates alkalies, destroys 

 the vitality of seeds, roots, &c, and kills vermin, 

 besides itself contributing to the fertilizing effects 

 of the mixture. 



Lime made from magnesian limestone, and 

 containing caustic magnesia, has been found to 

 act injuriously on many soils. 



Chalk is a variety of carbonate of lime ; besides 

 this substance, it usually contains 4 or 5 per cent 

 of other matters, which generally consist of clay, 

 sand, potash, soda, oxides of iron, phosphoric and 

 sulphuric acids. 



Chalk acts both mechanically and chemically 

 when applied to the soil. The principal mecha- 

 nical effects produced by chalk are the alteration 

 which it produces in the texture of the soil, 

 rendering soils which are light and incapable of 

 retaining a sufficient quantity of moisture more 

 compact and retentive; at the same time, by 

 this change in the texture of the soil rain is pre- 

 vented from washing away the soluble substances 

 necessary for the support of plants. 



All plants contain lime, and it may be con- 

 cluded that chalk, which is sparingly soluble in 

 water containing carbonic acid, acts partly by 

 supplying this necessary element. It has been 

 stated that chalk generally contains other sub- 

 stances besides carbonate of lime. Of these, 

 phosphoric acid, potash, soda, and sulphur are 

 all necessary to vegetation; and in practice it 

 has been found that the richer chalk is in these, 

 the more beneficial are its effects. 



Chalk is useful as an occasional dressing for 

 Vine borders, and for fruit-trees generally. 



