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THE TROPICAL AGRICULTURIST. 



[Jan I, 1887. 



ON THE IMPORTANCE OF LIMING. 

 The value of lime for agricultural purposes has 

 beeu kiiowu from a very remote period. According 

 to Plmy, the Gauls applied lime with great success 

 to their corn lands, while the Romans found an oc- 

 casional dressing very beneficial to vine.s and olives. 

 In our own country the practice of liming — that is 

 to say, the use of kiln-burued limestone — is confined 

 to certain localities. Thus, in Scotland, in the north- 

 ern and western counties of England and in South 

 "NVnles, it is much esteemed by practical farmers ; 

 while in the southern and eastern counties, where the 

 soil is naturally m ire calcareous and associated with 

 the upper and lower chalk formations, and where the 

 ehmate is diier and the rainfall less, it is not cus- 

 tomary to apply caustic lime, though great benefit 

 results from the use of chalk marl once in nineteen 

 or twenty years. It is to be feared that, with the 

 disappearance of the summer fallow, the practice of 

 liming has been neglected, and too much reliance has 

 been placed upon artificial fertilisers. This, if true, 

 is gi-eatJy to be n-gretted, inasmuch as, in order to 

 get the full benefit from any manure, it is absolutely 

 necessary that the land should contain a sufficient 

 supply of avail ible lime. We should remember that 

 not only is lime a necessary constituent of the min- 

 eral portion of all plants and crops, but it prom )tes 

 the more rapid decomposition of those organic matters 

 which are present in the soil, or which may be added 

 as manure — converting th^m, in fact, into nitrates 

 and carbonates. Further, lime exerci.ses an important 

 solvent action on the insoluble silicates which are 

 dormant in the soil, but which may be decomposed 

 by caustic lime, and made to liberate their potash 

 and sodi. Again, lime neutra'ises, all vegetable acids, 

 and is therefore especially necessary in the reclamation 

 of peaty land ; while on stiff clays it innproves the 

 physical character as well as the chemical composi- 

 tion, and thus promotes a more healthy ami vigorous 

 growth in the future crops. Listiy, its judicious use 

 is considered a specific on those soils which produce 

 turnips affected by the disease known as '" fingers- 

 and-toes;" and where aciil manures have been used 

 year by year, a good dressing of lime cannot fail to 

 be specially useful, and to insure the complete utili- 

 sa^ion of the soluble phosphate contained in super- 

 phosphates and dissolved bones. 



It is, therefore, evident that lime is a most important 

 element in aU fertile soils, and has been truly likened 

 to a key wirh which the stores of plant food may 

 be unlocked an) made available. Indeed, excessive 

 liming is most exhausting, and has given rise to the 

 old saying that lime is good for the father, but not 

 for the son. Liming should be followed, however, by 

 manuring, and then the full benefit will be obtained. 

 In the analyses of drainage waters from the Roth- 

 amsted experimental plots, made some years ago by 

 the late Dr. Voelcker, it was clearly shown that practi- 

 cally the whole of the nitrogen compounds which 

 were lost in the drainage water passed off in the form 

 of nitrates in combination with lime. Thus, from the 

 unmanured plot there were 687 grains of lime and 

 1'05 grains of nitric acid per gallon; while from the 

 ])lot manured with farmyard dung the drainage water 

 contained I0'32 grains of lime and 434 grains of nitric 

 acil per gallon. From the plot where 6001b. of sul- 

 phate of ammonia was applied per acre, the water 

 contained as much as 13 81 grains of lime and 4-55 

 grains of nitric acid. Lime, therefore, furnishes the 

 most effective carrier or fixer of the nitric acid as 

 fast as it is formed in the soil ; and we have every 

 reason to believe tV^at the composition of drainage 

 water presents us with the best idea how and in 

 what form plants take up their nourishment — at least, 

 so far as their food is in a soluble form. It also 

 appears from these interesting analyses that sulphate 

 of ammonia becomes decomposed during its passage 

 through the soil, sulphuric acid uniting with lime 

 and passing off in th'j drainage, while the ammonia 

 is retained in the soil, a portion only being lost in 

 the form of nitrate of lime. 



Having said so much respecting the value of lime, 

 let us briefly cousider the chief characteristics of the 



best qualities. Usually the most suitable limestone 

 for agricultural ])urposes is that which yields, after 

 burning, the purest and finest powder on slaking, 

 also the whitest and lightest lime ; for the less weight 

 per bushel, the better the quality. 



It is important that lime should slake readily and 

 break up into a fine powder, \s'hich can be easily and 

 uniformly scattered on the surface of the land, which, 

 if arable, should be subsequently harro;ved. Lime 

 should never be ploughed in, for it has a natural ten- 

 dency, as it becomes dissolved, to work downwards, 

 and beyond the reach of ordinary farm crops. Moun- 

 tain limestone yields excellent lime; as a rule, 

 1 ton should give on careful burning in the kiln, 

 about 11 cwt of caustic or quick lime. Great care 

 has to be taken not to overheat the kiln, for when 

 highly burned the lime will not slake readily. The 

 goodness or richness of different qualities of lime may 

 be noted by observing the quantity of water which 

 each sample will take up or absorb during the pro- 

 cess of slaking — the more the better, as the .superior 

 kinds swell out and increase in bulk from three to 

 four times their original size. 



Quick lime is soluble in 770 parts of water, and 

 has a hot alkaline txste, as opposed to the mild taste 

 of powdered chalk, which is only soluble to the ex- 

 tent of about two grains per gallon, or 1 part in 3,500 

 parts of water. 



It frequently happens that limestones from the 

 same district vary considerably, both in their physi- 

 cal properties and chemical composition, so that some- 

 times the less pure stone yields the better lim^, as 

 it slakes quicker and without water being specially 

 added ; moreover, it contains appreciable quantities 

 of phosphate of lime. In such cases, where any doubt 

 exists in the farmer's mind, it is desirable to have 

 the aid of chemical analysis before making a selec- 

 tion, especially where carting some distance has to be 

 considered. 



In addition to the mountain or carboniferous lime- 

 stone, which occurs so extensively in South Wales, 

 Sotnersetshire, Devonshire, and other counties, there 

 are very fair lias limestones — as, for instance, that 

 found at Aberthaw in Glamorganshire, which has a 

 great local reputation, chiefly, however, for building 

 purposes, as it sets and does not swell much on 

 slaking, so that it is better adapted for cement- 

 making than for agricultural purposes. 



In Pembrokeshire we find the Sulirian limestone, 

 also the Caradoc, which, although containing 80 per 

 cent of carbonate of lime, is regarded by geologists 

 as a sandstone, on account of its gritty formation. 

 Lastly, the oolitic limestones of Gloucestershire, and 

 the chalks of Kent and Sussex, form another 

 class which yields a great variety of caustic lime ; 

 but we have only space to observe that in most 

 cases, the softer the original rock, the poorer and 

 weaker is the lime. 



Now a few words reg.arding the kind of soils that 

 are improved by liming. It may be truly said that 

 there are few soils which are not benefited by the 

 occasional application of lime in some of its numerous 

 forms. 



On peaty land and heavy clays there can be no 

 doubt that slaked lime, applied at the rate of 4 or 

 5 tons per acre, will prove an economical dressing 

 every seven or eight years. 



On light sandy or gravel soils, as well as those 

 formed from the decomposition of granitic rock, 

 which are naturally poor in humus and organic re- 

 mains, much suiriUer applications are advisable ; thus 

 not more than one ton, or about fifty bushels per 

 acre, are perhaps quite sufficieut. Indeed, on such 

 soils it is generally safer to apply lime in the form 

 of ground chalk, chalk marl, shell sand, or in some 

 cheap form of phosphate and carbntiato combined, 

 such as the recently introduced basic slag, which in 

 certain localities can bi' obtained in a finely ground 

 state on moderate terms. Those who are familiar 

 with Cornwall are aware that immense quantities of 

 shell sand are sent inland annually, for application 

 to the arable land. This sea sand varies in its rich- 

 ness in carbonate of lime, according to the amount 



