44 THE FRUIT GROWER'S GUIDE. 



Marls and chalk owe their efficacy to the presence of carbonate of lime, which contains 

 nearly 44 per cent, carbonic dioxide, and 56 per cent, calcic oxide. When limestones 

 are burned the carbonic dioxide is driven into the air, calcic oxide only remaining 

 behind. This has a great affinity for water. When water is poured on the burnt lumps 

 strong heat is evolved, calcic oxide becoming calcic hydroxide, a new compound, made 

 up of water and lime chemically combined, and is termed quicklime. Exposed to the air 

 quicklime combines with carbonic dioxide, in time assuming its original condition by 

 becoming carbonate of lime. This is insoluble in water, calcic hydroxide or quicklime 

 being soluble in 732 times its own weight of cold water, the solution being known as 

 lime-water, and is useful to gardeners in driving worms out of the soil in pots and 

 destroying slugs. 



Newly slaked lime acts much more energetically when applied to land than either 

 chalk, marl, mild lime, or old mortar rubbish. Burnt lime after slaking is a fine powder, 

 therefore conveniently distributed, and when applied it combines at once with any free 

 acid in the soil. Acid neutralised by lime allows oxygen to act on undecayed vege- 

 table or organic matter, causing its rapid decay and the liberation of plant food. Humic, 

 carbonic, or nitric acids preserve organic matter from waste : hence organic matter in soils 

 deficient in salifiable bases becomes plant food very slowly, but when quicklime is applied 

 these acids become calcic salts, and food preparation proceeds rapidly. Not only so, but 

 sour soils are at once sweetened, heavy soils lightened, warmed and made earlier. 



Marl, chalk, and old mortar rubbish act similarly, but they have not the same energy 

 as caustic lime ; hence they are suitable for soils poor in humus or where it is desirable to 

 liberate food slowly. Caustic lime is applied with advantage to old garden soil ; indeed, 

 all soil containing much humus or vegetable remains is benefited, as such contains much 

 plant food in an unavailable form which lime liberates, enabling the cultivator to do 

 without manure for a time, the soil being otherwise improved. To light soils caustic lime 

 must be applied sparingly, and on virgin loams it must be used cautiously or the humus 

 necessary for fertility will be too rapidly dissipated. Heavy soils are much improved by 

 quicklime ; it curdles the clay, rendering it friable, whilst on sour bog land its action is 

 marvellous. For light soils carbonate of lime or chalk should form the dressing. 



lime supplies indispensable plant food, but it is rarely that it is applied as such, 

 'ihe ash of vine wood contains 30 to 45 per cent, of lime, that of its fruit usually 

 about 10 per cent. ; in some soils the lime has been so completely dissolved by carbonic 

 dioxide and washed away by rain that peaches and plums either fail to set, or cast their 



