DJTISIOy OF CUEMISTRY 97 



SESSIONAL PAPER No. 16 



may be summarized as follows : They furnish lime (which is an element of plant 

 food) in a more or less available form aaid consequently are valuable for soils, natu- 

 rally deficient in this constituent, as well as for soils that have loFt their lime by 

 long-continued cropping. They neutralize the acidity, of low-lying, ill-drained soils 

 and soils over-rich in organic matter, such as peat and muck soils; few farm crops 

 thrive in an acid or sour soil. They promote nitrification of the humus of the soil and 

 thus increase the amount of available nitrogen, the dominant element in crop growth. 

 They act on the inert potash compounds of the soil, setting free this element and 

 thus encouraging clover and other pol ash-loving plaiits. They also exert an influ- 

 ence on the insoluble phosphates of the soil, especially those of iron and alumina, 

 converting them into forms more readily utilized by crops. They improve the tex- 

 ture of heavy clay soils, making them mellower. 



The compounds, quicklime, slaked lime and carbonate of lime differ in their 

 composition and hence in their agricultural value. On the basis of an equal purity, 

 100 lbs. quicklime is the equivalent of 130 lbs. slaked lime and of 180 lbs. carbonate 

 of lime. In other words, it would require 2,600 lbs. slaked lime or 3,600 lbs. of carbon- 

 ate of lime (marl, ground limestone) to furnish the lime and do the same chemical 

 work in the soil as 2,000 lbs. of quicklime. 



The rate of application per acre will depend on several factors — the character 

 of soil, degree of its acidity, etc., but it may be stated as a general principle 

 that on light and poor sandy loams the dressings should be small, say from 500 lbs. to 

 1,500 lbs. per acre of quicklime — the equivalent of (about) 900 lbs. to 2,700 lbs. of car- 

 bonate. On heavy clay loams and on soils rich in vegetable matter heavier applications 

 may be made, say from 1,000 lbs. to 4,000 lbs. quicklime — the equivalent of 1,800 lbs. 

 to 7,000 lbs. carbonate of lime. In considering the amount, the frequency of the appli- 

 cation must be borne in mind. It is undoubedly better to give small and frequent 

 dressings than large ones at long intervals. Under ordinary conditions even when 

 a soil responds well to liming, from 5 to 10 years should be allowed to elapse betweeen 

 dressings. 



While excessive amounts of quicklime, or its too frequent application, may do 

 postive harm, no danger to soil or crops need be apprehended from large dressings 

 of marl or ground limestone. Quicklime and slaked lime are probably best applied 

 in the autumn, marl and g-round limestone may be put on the land at any season. 

 Quick lime, known commonly as stone lime, is somewhat inconvenient and dis- 

 agreeable to apply unless it can be bought in a ground condition and distributed 

 with a fertilizer drill or lime spreader. Without special means for distribution the 

 best plan is to put the lumps of lime in small heaps, say of 50 to 75 lbs. each, placed 

 at intervals, according to the rate of application, on the ploughed soil. Over each 

 heap pour slowly a little water, say 2 to 3 gallons, and cover with soil. When the 

 lime is thoroughly slaked, the fine powder may be mixed with more soil, scattered 

 and at once well harrowed in. Crushed marl and ground limestone offer no difficulties 

 in their application. Uniformity in the distribution of all these lime compounds 

 is desirable and since there is a tendency for the lime to wash down, they should 

 not bo ploughed under but spread on the surface and harrowed in, as already 

 described. 



The use of lime entails the constant supplying of organic humus-forming 

 matter to the soil if fertility is to be maintained. 



Lime alone must lead to a soil's impoverishment and in time to its exhaustion 

 below the point of profitable cultivation. In a system that is periodically adding to 

 the soil's store of vegetable matter, as by the regular application of farm manures and 

 the adoption of a rational rotation whereby plant residues arc returned, the occasional 

 application of lime in one or other of these forms may be found desirable and-profitable. 

 Laboratory No. 1121S. — From Mount Carmel, Antigonish Co., N.S. ; occurs as 

 a large bed or deposit; moderately soft and of a reddish-grey or yellowish colour and 

 16—7 



