THE USES OF LIME IN AGRICUL TURE.

Waikato Times, Volume XXXIV, Issue 2790, 31 May 1890, Page 6 (Supplement)

THE USES OF LIME IN AGRICUL TURE.

A short disoourso was delivered by Mr H. R. Hyatt at the last meeting of the Waikato Fanners' Club, at Cambridge. It contains a quantity of information that is greatly needed by farmer's, whom we therefore recommend to peruse it carefully. Mr Hyatt said: Limestone is very widoly distributed in nature. Its most common form is that of carbonate of lime, of which there aro many varities such as marble, chalk, limestone-rock, etc. A piece of the latter kind from the Upper Waipn district was given to me at tho last meeting of the club by Mr Forrest. On analysis I find it a very pure specimen, consisting almost entirely of carbonate of lime, with a small percentage of iron pyrites. It is remarkably free from sand or silica which is generally moro or loss associated with limestone formations. Both the carbonate and tho pyrites will be useful additions to our soils. During the process of burning tho pyrites would be likely to form sulphuric acid, which in its turn would unite with the limo and form gypsum or sulphate of lime. This form of lime is tho best as a manure, and, if procurable, is generally recommended by experts for manure mixtures, as its ready solubility renders it at once available as plant food. It is much used in America under the name erf plaster. Carbonate of lime and quick-lime, however, affect soils in a different manner, as I shall presently show. Our Waikato coal is also much impregnated with pyrites, and as this would be used for burning the lime, it would most probably increase the amount of Bulphate of lime formed during the process of burning. Tho iron contained in the pyrites would not be required by our soils, as they aro sufficiently supplied with that element already, but the small amount contained in the Waipa lime would have no injurious effect. Carbonate of lime is sometimes | used in its natural state in the form of chalk, marl, or shell sand, and sometimes it is burnt and applied to the land in a caustic state. For light soils deficient in organic matter, as tho Waikato soils are, it is preferable to use the unbufnt, or as it is frequently called mild lime. Qnick lime rapidly burns up tho organic matter in the soil, so if this be deficient, exhaustion may ensue. It is, however, an open question whether the other benefits derived from the use of lime make lip for

this loss. Waikato farmers might settle this question for themselves by trying the effect of applications of both mild and quick lime on small patches of land. The Waipa lime, however, is of sueh a hard tenaceous nature that the cheapest and most available way of bringing it into a fully powdered state, fit for agricultural purposes, would be by burning—whether required in a caustic 01 mild form, Carbonate of lime consists of a chemical compound of lime with carbonic acid. If it be exposed to a great heat in a kiln for over 48 hours the carbonic acid will be all driven out by the heat, and caustic or quick lime is tho moro or less pure lime that is left aftsr the c irbonic acid is thus extracted from it. It is very difficult to keep it in this state, as it exerts itself strongly for a reunion with the carbonic acid, and if left exposed to the air, which contains a certain amount of carbonic acid, it will soon return to its original form of carbonate of lime, nr mild lime. But this advantage is gained ; after lime has burnt, if water be poured upon it, it immediately falls to a fine impalpable powder, and in this form it is known as slaked lime. On lands that are rich in organic matter it is advisable to harrow in tho lime immediately after slaking, and its strong affinity for carbenio acid will cause it to decompose tho organic matter, driving therefrom the carbonic acid with whieh it unites, and it again returns to the form of carbonate. On light soils deficient in organic matter it is possible that this burning up or rapid decomposing of tho organic matter might have a prejudicial effect, This could be avoided by exposing the lime, after slaking, to the influence of the air. It would thus absorb carbonic acid and brcotno

1 carbonate or mild limo. In this state it 1 would not so rapidly exhaust the organic--1 matter, and in most other respects it ' would act the same. In agriculture the ' usos of limo are three-fold. (1) It fnr- ' nishea food necessary to all cultivated crops; (2) it acts chemically on the con--1 stituonta of soils ; (3) it ha* a mechanical effect on soil*. As a plant food : All plants require lime ; otherwise they would bo deficient in bone-making material a* a food for animal*. Animal-* require lime to supply the g-rowlh aud repair tho waste of their bones, and as they can as-f-iiniLite it only iu the form of vegetable or anitnal matter, they must get it through the vegetable kingdom. Mineral food, as such, not only is unnecessary to animals, but is also positively injurious. Minerals cannot enter the plant except in a soluble form. Carbonate of limo is soluble in water only to a very slight degree. It is, however, acted upon by the carbonic acid, which the rain washes down from the air, and it thus becomes much more soluble. This carbonic acid is accountable for many of the chemical changes which take place in the laboratory of the soil, aud it would be a great advantage to farmers to be acquainted therewith, as such a knowledge would be of great value in the choice and application of manures. A glance at the analysis of any cultivated crop will show the importance of lime as a plant food, especially to turnips and clover. A crop of 17 tons of turnips carries off about 74-lbs of lime, 2 tons of clover carries off about SGlbs, and other crop 3in smaller quantities. Chemical action of lime: But besides being itself a plant-food, lime improves the health of plants in other ways, and renders other minerals capable of being assimilated by plants. This

chemical action which it exerts upon soils affecta them in four different ways, (t). Lime in the state of either carbonate or quick lime (but more quickly in the latter case) haitous the decay of organic , matter in the soil, and thus Bets free the 1 ingredients contained in the dead organio matter to be again assimilated by the growing crop. This action of lime may be regarded as stimulating, and if continued without the addition of other manures tends to exhaustion, as illustrated by the old proverb ; " The use of lime without manure will make both farm and farmer poor." (2). During the decay of organic matter in the soil, oertain acids are found which make the land sour, and give a tough, stunted, wirey character to the herbage, which is thus rendered unpalatable and unprofitable as a food for stock. Lime unites chemically with these acids, and thus counteracts the sourness of the land. It has been found that in cases where part only of a large paddock has been limed, that sheep confine themselves almost entirely to this part, and it, being continually enriched by their droppings, assumes in time the appearance of quite a different soil from that which has not been limod. Thus the beneficial effects of liming may often be distinctly traced after a period of thirty or forty years. (3). Lime has also a tendency to split up certain iusoluble compounds in the soil, and thus helps to render dormant matter active and available as plant food, It acts in the same manner on compounds containing ammonia, setting free the latter in the form of gas. Should this action take place in the open air the ammonia will be entirely lost j therefore lime and manures should be applied separately to the soil, and not be allowed to come in contact until they are in the soil, when the soil will absorb the free ammonia and prevent its waste. Strange as it may appear, lime has just the opposite effect upon certain chemical componudg, For example t— in cor-

tain combinations is verysolu hie and would be_ quickly washed out of the s<il by rain, but if lime be present it changes place with the potash, forming new compounds, and that valuable manure is retained in the soil. (4). Formation of nitre: During the decay of organic

matter in soils, lime also helps in the slow, natural production of nitric acid. This nitric acid again unites with the lime, and forms nitrate of lime—a substance very soluble in water, and therefore available as plant food, furnishing the plant with nitrogen. TliU3 a manure too costly, perhaps, for the farmer to buy is produced for him in the soil by the action of lime. Mechanical action: Upon heavy clay soils lime in any form acts beneficially, by making them lighter and more easily worked, and, also, more open to the air and rain. Though this does not apply to light soils, yet these are also benefited by the application of lime, as the waste of soluble manures by rains is thereby very largely prevented, as I have already shown. Application : Lime was much more extensively used in former times than it is now. Indeed, with the exception of stable nanure, it was the only manure used. Perhaps it war too largely used, but it is probable that we have now gone to the other extreme, and our soils are suffering for the want of lime, just as in past times they suffered from an overliberal supply. In light soils tho frequent repetition of small doses seems to be the most advisable, but at the same time an effort should be made to keep up the supply of organic matter in the soil, as this is quickly exhausted by the action of the lime. For this and other reasons I think it would be preferable to use the lime in its mild form. To do this it would be necessary only to allow the quicklime to lie on the surface for a day or two before it is harrowed in, aa it would absorb carbonic acid from the air and return to the form of carbonate of lime. The process of burning, I believe, would be both the cheapest and most effective mode of pulverizing it, even when it is not required in the form of quicklime. However, it would perhaps be advisable for the farmers to try the experiment on a small scale for themselves in order to see whether our local light sundry soils would be more benefited by the use of quick or mild lime. Under any circumstances there can be no doubt that a supply of lime is very necessary to successful agriculture, and withextensive riciges of limestone hills within view of the whole district the

local supply of this valuable material is practicable inexhaustible. The only expense would be the carriage and burning and this should not exceed ten or fifteen shillings a ton. Seeing that this is about the only traffic that can at present be developed on the Te Kuiti railway line, one would think that the Government would be anxious to create a demand for the article by a system of very low freight.