The Journal of Agriculture.

New Zealand Journal of Agriculture, Volume XII, Issue 5, 20 May 1916, Page 339

The Journal of Agriculture.

WELLINGTON, NEW ZEALAND. 20TH MAY, 1916.

LIMING.

PRINCIPLES AND PRACTICE.

A. McTAGGART,

M.S.A., Agriculturist.

THE term “ lime,” though it usually refers to the burnt, oxide, : quick, or caustic form of lime, through long usage of this form for -building and agricultural purposes, in reality embraces various salts of the metal calcium. In nature calcium is found principally in two formsas calcium carbonate (limestone) and as calcium sulphate (gypsum). By far the greater portion of this metal. is found in. the . carbonate form, . and this is of organic origin, - being for the most part the remains of early minute marine life 'known as foraminifera. Lime has -been used for -agricultural purposes since the dawn of agricultural history, and it is interesting to note here that in those early times and onwards it was"[the calcium, carbonate, in

the form of chalk or marl, that was used for soil-improvement. That this great soil-improver is needed in most parts of New Zealand, whose soils for the most part are well supplied with acidity and, in many instances, are in an unsatisfactory physical condition, is now generally recognized by our farmers. But what really is required by the farming community generally is a clearer understanding of the chemistry of lime, of the properties and uses of lime in agricultural practice, of the forms in which lime should be applied to suit 'special soil-conditions, of the distribution of lime in its various forms, and of the economics of liming with special reference to purchase, haulage, and forms and quantities to apply under varying conditions. This article is an endeavour to assist towards a better apprehension of these factors. ' FUNCTIONS OF LIME. . . , There are two principal : effects produced .by applying lime to soils. One of these is to furnish a base for neutralizing the acids that may exist in the soil or that may form as the result of such necessary processes as nitrification. Through the decomposition of organic matter (vegetable and animal) by bacteria, available or soluble nitrates are ' finally . formed, but acids of various kinds (principally humic acid) are produced. These latter require to be neutralized by a base to keep the soil fully productive. As a result of this continuous breaking-down process yielding free acids the bases in the soil (principally lime) are being gradually used up for neutralizing the .acidity. thus produced. Strictly,, acidity does not accumulate in the soil, but by finally neutralizing all the lime present it renders the soil sour. Such a soil, .requires lime to render it fertile, or, in ' other words, to supply a base for the neutralizing of acids continuously, being formed by bacterial activity and for the formation of nitrates by the nitrifying bacteria. The acidity arising from the application of acid fertilizers such as superphosphate, sulphate of ammonia, &c., , and from the toxic substances believed to ■ be given off. by plants, particularly fern and manuka, in like manner calls for a base to neutralize it.

In addition ■ to the above-mentioned function of a base is that of supplying a mineral in small quantity for the ready formation from ammonia and ; nitric acid of the nitrate itself, in which soluble form alone a plant can take up its food. From this we glean that a predominance of evolved acidity and an almost total absence of lime are decidedly detrimental to the formation of the desirable nitrates by bacteria. In short, the nitrifying bacteria are for the most part inactive in a predominatingly acid (sour)

soil. To correct or neutralize that acidity is therefore important. Indeed, the chief reason, and usually the only justifiable reason, for applying lime to soils is to correct or neutralize soil-acidity. The other principal effect of applying lime to soils is that of promoting a more active decomposition or destruction of the soil itself, especially of its organic matter or humus content. The reserves of raw material, organic and mineral, are in part (varying with the form and quantity of lime applied) released and converted by chemical and bacteriological action into available or soluble plant-food. The decay of vegetable and animal matter and its

conversion into a soluble form are accelerated. Potash and to some extent slowly soluble natural soil phosphates are released and converted into available or soluble forms. It is largely due to the previously unavailable potash, held -in close association with the silicates, in clay soils, being released or made available that we find lime giving specially good results on such soils. The need for potash manuring will for a time be eliminated by liming soils, but there will come . a time, especially .on the lighter soils, when potash manuring in some form will’ have to be practised. On the heavier soils, which are as a rule abundantly supplied with humus, the

organic matter decomposes slowly, and lime is of special value for accelerating'this decomposition. ' On the other 'hand,'where a soil is not very well supplied with humus, as indicated by the absence of or deficiency in good dark Colour and by floury texture, the burnt lime in particular; if applied in anything but small quantities, results in injury to the . soil through causing a rapid decomposition of what little humus ’is present. Burnt lime, in anything but small applications, rapidly exhausts light lands, due principally to the' loss from the humus into the. air of nitrogen in ammonia form and into the subsoil by leaching of nitrates. ' Other effects of lime, of lesser importance than those above enumerated but more or less closely associated therewith, are the following : Lime mellows heavy and clayey soils by flocculating . the colloids of the clay, thus making the soil more friable and permeable. Both drainage and capillarity (natural upward flow of soilwater), also the aeration of the soil, are therefore improved, and the soil is less likely to become over-compact and to bake and to crack. The maintenance of tilth 'is therefore more easy. The aeration of the soil also promotes the activity of soil bacteria which prepare the raw materials for use by the young growing plant. On the other hand, lime compacts loose open soils. The warming of the soil, by lime improving its aeration, also has a decided bacteriological effect. . Phosphatic fertilizers are often rendered more effective. This seems to be especially true of the less soluble fertilizers, such as finely ground rock ‘ phosphates. Indeed, all fertilizers would appear to be rendered more: effective by > the use of -lime applied well beforehand, and especially is this true of the acid fertilizers. A moderate application of lime, especially if used in connection with green-manuring or an application of farmyard ; manure, will increase the capacity of the lighter soils to retain moisture. --Then there is the action of lime in the conserving of free phosphoric acid, which exists naturally in the soil or as the product of phosphatic manuring. The lime combines with this free phosphoric acid, converting it into a slowly soluble phosphate and thereby holding it for subsequent crops.

The presence of lime in the soil is highly unfavourable to the parasitic organisms which are the cause of certain diseases. Most important among such diseases is club-root of turnips, swedes, cabbages,, and other cruciferous crops. Heavy . dressings of burnt lime will, as a rule, destroy the acid-loving organism responsible for this disease. If the soil is badly infested, lime may not prove a ' complete prevention, but the free use of burnt lime without doubt greatly decreases the tendency for this and other fungus diseases to attack farm crops.

.. The nutritive value and palatability of grasses are improved to some extent, also , the health of stock, as the result. of -, applications of. lime to land. In general, a nutritious herbage results, and the . increased supply of flesh- and bone-forming materials promotes thrifty, healthy animals. .. .

Finally, there is the important function of lime in greatly stimulating the growth of legumes, particularly lucerne and clovers. These most valuable fodder plants, being nitrogen-gatherers, enrich the soil in that valuable constituent, and to a greater degree when they are well supplied with lime. (There is no plant that. requires lime to a greater extent than lucerne.) Thus, lime is indirectly a nitrogen-gatherer, the soil-air being the source of supply and the bacteria in the nodules on the roots of legumes . the direct agents in. this gathering process. Lime also beneficially influences the . few forms of -symbiotic bacteria in the soil, or those that draw nitrogen from the air without the assistance of leguminous plants. . ~ ■ .

From the above-mentioned facts it will be seen that lime is indirect in its action. In itself it is not a manure, for it is assimilated by plants, except by - lucerne and red clover, in only very small quantities. ■ Its great function is not as a manure, but as a releaser or preparing agent of soluble plant-food constituents, and - its action in connection with those processes is threefold—physical, chemical,, and biological or bacteriological.

INDICATIONS OF THE NEED FOR LIME.

The presence in quantity of sorrel and of other . acid-loving plants such as spurrey (yarr), moss, horsetails, blackberry, foxglove, bracken, manuka, and the inferior bent grasses (principally red-top and florin) are, as a rule, indicative of a sour soil and that applications, of lime will be decidedly beneficial. Sorrel has, however, been known to ' thrive ■ hid’, a soil which has been heavily limed, due to other, deficiencies in the soil preventing the grasses and clovers thriving sufficiently to crowd out the sorrel; but as a rule the liberal use of lime on the average soil will stimulate the grasses and clovers to such an extent as to crowd out or keep in check the sorrel. . The presence of acidity encourages sorrel, while a liberal application .of lime stimulates the valuable grasses and clovers to • a much greater extent, the result being the ascendency of the latter.. ■ . . •

Where clovers and the better grasses, such as timothy and rye grasses, but especially clovers, will not thrive, lime as a rule is required. • The clovers ■ either become sickly-yellow or disappear.

On cold clay soils we frequently find the better grasses and clovers giving place to the inferior bent grasses, such as florin and red-top. As already indicated, these latter grasses like sour soils, and lime is required to encourage the superior vegetation. Foothill lands and lands at the base of hills are frequently sour, the characteristic vegetation being the bent grasses. Here liming is badly required, but drainage has frequently to be attended to first. There are in New Zealand thousands of acres of sour soils, for the most part clays or clay loams, of this class that specially require lime.

When a soil is sour it will turn blue litmus paper placed in contact with it red. To carry out the test make a small quantity of soil into a thin mud with pure water, and after its has stood for a short time place a slip of blue litmus paper on it and cover with the mud. After about ten minutes remove the paper, washing it, if necessary, in pure water to show the colour. If the paper has turned red the soil is sour and needs an application of lime to sweeten it. The litmus-paper test can also be made by inserting a slip of the blue paper into an incision made in the soil (stripped of its surface vegetation) with a knife and by pressing the soil firmly on either side of the paper. Practically all chemists keep litmus, which can be purchased very cheaply.

From the chemical standpointaccording to Dr. A. D. Hallany soil that contains less than I per cent, of carbonate of lime can be improved by liming, and any soil containing less than o-2 per cent, of lime carbonate cannot make proper use of fertilizers applied thereto. .

Soils that are refractory or stiff and hard to work, as, for instance, most clay soils; drained swamp soils; light open soils; soils that have been cleared of fern or manuka ; soils affected with, club-root of turnips; soils which do not grow clovers well; soils well supplied with the acid-loving plants enumerated above; and soils upon which superphosphate has been used for years—these are in greatest need of lime.

FORMS OF LIME TO USE.

The forms of lime commonly used in . agricultural practice are burnt .lime and carbonate of lime (ground limestone). The former should only be used in quantity (heavy or moderately . heavy dressings) on soils well supplied with humus as indicated by good dark colour to . a fair depth. It has the tendency to burn out (oxidize) the humus, and for this reason is inclined to be exhaustive, particularly on light lands not very well supplied with organic

matter. The old adage, “ Lime and lime without manure makes both farm and farmer poor,” refers to this exhausting effect of burnt- lime, and not to the mild and inexhaustive carbonate of lime. Of ' course, burnt lime in quantity could be used even on light lands if provision were made for the keeping-up of the humus-supply by periodic applications of farmyard manure or by systematic green-manuring. But in this country we produce little farmyard manure, and we have no guarantee that farmers as a whole will seriously adopt systematic green-manuring.

From the point of view of haulage, however, burnt lime is the more economical form to use, provided too heavy dressings are not applied, for 56 lb. of the burnt lime is equivalent to 100 lb.

of the carbonate form. In other words, if a farmer purchases 100 tons of carbonate of lime (ground limestone) he'will have in reality only 56 tons of lime— is, lime in the burnt or oxide form. The balance (44 tons) will consist for the most part of a gas known as' carbon dioxide; and there is . usually plenty 'of this gas in . the soil-air, for it' is given off by the roots of plants. The haulage of this extra 44 tons a distance from the railway is therefore to some extent an economic loss. This points to the use of burnt lime on soils situated some . distance beyond the 100-mile railway limit from the source of supply, or located back from the railway, a distance that has to be - considered . in '.the.. haulage, of materials. On the lighter .of such soils so situated burnt lime should be used only in comparatively small quantities and at a

little more frequent intervals than where moderately large dressings are applied to strong soils —soils well supplied with humus.

For soils within striking- distance from the railway, and not situated more - than a few miles beyond the 100-mi le limit of free railage, the ground limestone could, more- economically -be used on’ all soils, but particularly on the - lighter soils, provided the price is not more than one-half to two-thirds -of that charged for burnt lime. In- other words, where 20s. per ton is -charged for burnt lime not more than ns. 3d. per ton should be charged for carbonate „ of. lime. But other factors render carbonate of lime worthy of a higher value than that just calculated by comparing the two forms -on the basis of calcium-content, These factors are the inexhaustive nature of carbonate of lime and its consequent suitability for application in large quantities to all types of soil; its agreeable condition to handle for both man and horse as compared with burnt lime; the. absence of danger in haulage or in storage when the . material gets wet-; its special value as a base for nitrate (soluble plant-food) formation; .and its action as a carrier of' carbon dioxide, whose component parts (carbon and oxygen) are ... essential plant-foods, and in this form add to what are already enclosed in the soil. Relatively, therefore, anything up to about 15s. per ton: may be considered a legitimate price for firstgrade carbonate of lime compared . with 20s. for the burnt, caustic,, oxide, or quick form of lime. .• .'Moreover, when burnt lime is applied to the land it - ultimately " returns . to the carbonate form by taking up carbon dioxide from the soil-air.

If we were 'to trace the history of the use of the burnt form of lime, we would find that the early agriculturists found that the only practicable way in those early times to render the limestone available for application to the land was to burn the rock, from which form it fell away to a powder (slaked) upon applying water to it. But to-day we are living in an age of machinery, and powerful machines are manufactured for grinding rock to a powder, thus making limestone available by means other than burning for use on farm lands.

Soil chemistry and field experiment have revealed to us the value of powdered ’ limestone for agricultural purposes and of its' equal or, indeed, superior merit as compared with burnt lime for soils requiring lime. In support of this assertion one cannot- do better than quote directly from the writings of Dr. C. G. Hopkins, of Illinois University, one of' the foremost authorities in America on soils. ■ Dr. Hopkins states,—

“ The most extended investigation ever conducted relating to the use of burned lime and ground limestome in comparative tests is

reported by the Pennsylvania Experiment Station (Report, 1902). Four plots were treated with burned lime (slaked before . being spread) at the rate of 2 tons per acre once in four years. Four other ’ plots were treated with ground limestone at the rate of 2 tons per acre every two years. A four-year rotation was practised, consisting of corn (maize), oats, wheat, and hay (mixed timothy and clover) seeded on the wheat land in the spring. ■ By having four sets of plots,C each crop was grown every year. Seven products were obtained and weighed each year namely, corn, corn-stover, oats, oat-straw, wheat, wheat-straw, and hay. After twenty years’ results had been obtained (1882 to 1901), the Pennsylvania Station reports data showing that with every product a greater, total -yield had been obtained from the plots treated with limestone than from those treated with caustic lime. Furthermore, with every product whose total yield for the last eight years of the experiment was greater than the total yield of the first eight years the limestone produced a greater increase than the caustic lime ; and with every product whose total yield for the last eight years was less than the total yield of the' first eight years the decrease was less where limestone was used than where caustic lime was applied (oat-straw alone excepted). This is significant, in that it demonstrates the tendency of caustic lime with continued use to exhaust or destroy the fertility of the soil. In discussing these investigations, Dr. Frear, of the Pennsylvania Station, says ‘ln each case the yields with the carbonate of lime showed superiority under the conditions of this experiment over those following an equivalent application of caustic lime.’ “ After these experiments had been in progress for sixteen years the soil' of each of the four plots in each test was sampled for analysis. The average nitrogen-content for the - four plots receiving ground - limestone was found to be 2,979 lb. per acre to a depth of 9 in., while only 2,604 lb. were found in the soil treated with caustic lime. This difference of 375 lb. of nitrogen is equal to the nitrogen contained in 371 . tons of farm manure. In other words, the data indicate that the effect of caustic lime as compared with ground limestone was equivalent to the destruction of 371 tons of farm manure -in sixteen years, or more than 2 tons a year to the acre; or, if we count the .soil, nitrogen worth 15 cents. (7|d.). a pound (a fair market price), there is a liberation of more than $7-00 (285.) worth of nitrogen for every ton ,of burned lime used during the -sixteen years. “ The Maryland Experiment Station has recently reported experiments with different . kinds of lime, covering ■ eleven years, with a rotation of corn, wheat, hay (timothy and clover), 1,400 lb. of calcium oxide (burned lime) and equivalent amounts of calcium carbonate (ground oyster-shells and shell marl) having been applied per acre at the beginning. Four crops of corn, three of wheat, and four crops of hay were harvested during- the' eleven years. In commenting. on the results, Director Patterson, of the Maryland Experiment Station, says, ‘lt will be noted that the carbonate of lime gave decidedly better results than the caustic lime.’ Porter and Grant, in a recent Farmers’ Bulletin issued by the agricultural department of the County : Council of Lancaster, England,

report experiments on manured and unmanured meadow lands, showing that ground limestone is more profitable as an application to grass lands than burned lime, and that it can be economically used on grass lands which are in need of lime.

"No trustworthy investigations support the use of burned lime in preference to ground limestone ; although we have ample information showing that on many soils a moderate use of burned lime in connection with a liberal use of farm manure and green manures yields profitable returns, which would, no doubt, be still more profitable if the burned lime were replaced with ground limestone."

Such indisputable evidence shows clearly the superiority of powdered limestone over caustic lime in actual agricultural practice ; but the decision of the farmer as to which form he shall purchase must be determined mainly by the forms purchasable, by the market price of each form, and by the location, of his land with respect to the source of lime-supply and to distance from the railway. Where these considerations are negligible the evidence is in favour of the use on all soils of the carbonate of lime.

As to the relative availability (solubleness) of burnt lime and carbonate of lime .the former is quicker in its action. undoubtedly, but the carbonate, if in a finely divided condition, proceeds to do what is required of .it (chiefly to neutralize soil-acidity). without undue delay. In other words, when finely ground it is for all practical purposes comparable with burnt lime in readiness of action; and particularly is . this so in . a damp climate . where as a rule soilacidity is most marked. Acidity of the soil in- a sense is a blessing in disguise in that it renders . more quickly available or soluble the. ground limestone than would obtain' under drier and less acid soil-conditions. As might be expected, the burnt lime would produce a greater increase in the crops for the first year or two than could be produced by the ground limestone, more especially where the minerals phosphorus and potassium are not applied, the reason being that ground limestone produces only the milder action chiefly that of correcting the ■ acidity of the. soil and thus encouraging the multiplication. and activity of the nitrogen-gathering and nitrifying bacteria. ’ The burnt lime not . only produces this same effect, but it also acts as a powerful, soilstimulant, or. soil-destroyer, attacking and destroying the organ 1 c matter, and thus liberating plant-food from the soil, resulting in more or less waste of valuable nitrogen and humus. This latter result takes place particularly when heavy or moderately heavy applications of burnt, lime are applied'to the land,. particularly to light land. . " ,

Carbonate of lime in finely divided form has been found occurring in a natural state - in very large quantities in various

parts of Canterbury, Marlborough, . and southern Nelson. It is also known to exist at Lake Hayes in Otago, and occurs in parts of. the east coast section of the North Island. Such deposits are of very, great agricultural value, and the farming . community generally should appreciate that fact sufficiently so that. adequate steps might be taken by the farmers themselves to make these deposits available at a reasonable cost for application to widely scattered sour soils.

To test the naturally ground carbonate of lime from the Waikari deposits, and generally to provide further evidence of the value of this form of lime (under New Zealand soil-conditions), an- extensive series of demonstration, experiments were initiated last spring throughout the Canterbury Province by the Fields

Division of the Department. Differing quantities of burnt lime and of carbonate of lime were . sown on plots to be manured and unmanured alternately. The crops sown were either turnips to be followed by grass sown in 1916, or rape with grass sown at the same time.. The effects of the various forms and quantities of lime are to be followed in the grass crop from year to year for the next few years. It is expected that the burnt lime will give the best results in the early stages of the experiments, for reasons mentioned above, but as time goes on the carbonate of lime will be expected to present the best showing. The past season has been dry in Canterbury, consequently no signs of results' can be expected at the close of this autumn. Next .. spring the first results may be looked for.

Field experiments have already demonstrated near Auckland and at Marton Junction the value of ground limestone, especially when used in large quantities with small applications of fertilizers. At Marton Junction remarkable results were obtained with carbonate of lime applied at the rate of 4 tons per acre, together with a quantity of wood-ashes. (See Journal, October, 1915, P- 295.) Limestone-crushing plants are in operation in various parts of New Zealand, and the work of pulverizing the rock is still being made the subject of experimentation to some extent. Nevertheless satisfactory machinery is obtainable for the production of this acceptable form of agricultural lime.

. From the foregoing discussion it will be noted by farmers generally that there is . a place for carbonate of lime as well as for burnt lime, the form to use being determined by the soil, location from the source of supply, and the market price of each form (assuming that both forms are obtainable in a particular region). Where the application of lime as lime itself to land requiring it is beyond the ability of any farmer, due to distance from the source of supply, it can be gradually introduced into soil by the use of basic phosphates (principally basic slag and basic superphosphate) when periodically manuring for crop production. The process doubtless ■is slow, but “half a loaf is better than no bread.” ' .

THE APPLICATION OF LIME. The rate at which lime should be applied to land depends upon the soil and to some extent upon the climate. An analysis of the soil is the only reliable guide as to whether or not a soil' lacks in calcium carbonate, and, if this were carried out, the rate of application should as far as possible be accurately gauged from the result. There are certain natural evidences, enumerated above,, of the urgent need for lime, but the approximate quantity to use on a particular. soil can only be determined by analysis or by a system of carefully conducted experimental plots carried through several years.

According . to.. Dr. Hopkins, no fixed limits can be placed as yet upon the amounts of limestone to use as an initial application to acid soils. One ton to the acre, he says,’ is more than enough to destroy the acid commonly contained in ploughed soil, provided the limestone is sufficiently fine and thoroughly mixed with the soil.;--'- but, as a rule, it is less expensive to apply more limestone and then to allow the mixing to go on more slowly by the necessary - processes of ploughing, disking, harrowing, &c., in the regular farm operations, keeping in mind also that the heavier the application the longer it will last. He further states that there is more or less acidity brought up from the acid subsoil, especially in time of drought, and that there should be sufficient limestone

in the surface to destroy this acidity as it rises. While a small amount of acidity in the surface may not be a serious injury when the rainfall is abundant, there, is apparently in humid regions some rise of acidity from strongly acid subsoils in times of partial drought, corresponding somewhat to the “ rise of alkali” in arid regions, where the water leaves the soil only by evaporation from the surface. From these remarks of a noted authority on soils one would judge that in a humid climate an application of limestone is just as necessary during a partial drought (to neutralize the risen acidity) as it is during periods of plenteous. rainfall (to neutralize the acidity in, and being washed into, the subsoil). The moderately frequent applications of fair quantities of ground

limestone in such climates seem necessary to keep this acidity neutralized in soil and subsoil. Fortunately there •is no danger of applying too much ground limestone to soils. At Rothamsted Experiment Station, in England, a century or more ago, certain fields were given heavy applications of chalk, dug out of pits excavated for the purpose, and the fact that some of these fields still' contain 50 tons of calcium carbonate per acre in the ploughed soil and continue with fair treatment to produce good crops is proof sufficient that there is no danger of applying too much ground limestone. Dr. Hopkins advises .an application of at least 2 tons of ground limestone per acre, where the addition of limestone is necessary,

believing that less than - this will not give satisfactory results in practice. Heavier applications, he states, will give greater ' profits per acre, but probably less profit per ton of limestone used. ■ He further advises that if one must cultivate much land, and can use but little limestone, he should apply 2 tons per acre and plan to apply more in later years ; but if one cultivates less land and wishes to improve it more rapidly he should apply 4 to 10 tons of ground limestone per acre, and it will give more marked results and will last much longer. As to investigations reported with regard to the losses of calcium carbonate from soils at Rothamsted (England) he states that practice based thereon would require an application of 2 tons per acre of ground limestone about every five or six years, in order to replace the regular losses. Where burnt lime is advisable, under average soil-conditions at least 1 ton per acre every five or six years should be necessary on the basis of carbonate of lime experience of Rothamsted and Illinois. In the event of a soil being decidedly acid but well supplied with organic matter-as, for instance, a drained swamp soil —from 1 to 2 tons per acre every five or six years should be necessary. Where light lands requiring lime • are situated some distance from the railway or source of supply, thus necessitating the use of the burnt form of lime, applications of 5 cwt. to 10 cwt. per acre every two or three years are decidedly preferable to 1 ton per acre every five or six years. The smaller applications of caustic lime on light soils are certainly more conservative of fertility than the heavier applications. Of course, the burnt (more concentrated) lime could be air-slaked by spreading out in an open shed for at least six months, and thereby rendered suitable for application in large quantities to light soils through reversion to the carbonate form. <- Lime can be applied to land at any time during the year, but the time it is applied is usually governed by. convenience. In districts where the roads are inferior the summer or autumn is the most suitable period. During this part of the year the limeworks are not so busy, and quick delivery of the order can usually be relied upon. Besides, by applying in the autumn the lime shows results in the following spring, and this applies especially to the carbonate form. When applied in the autumn or early winter lime is washed into the soil by the rains of winter, and the subsequent tillage operations complete the distribution of the material throughout the soil. Of course, lime, and especially the burnt lime, can be applied to land in early spring and show results during the following summer and autumn, particularly in a humid climate,

but more satisfactory results will be obtained if the lime is applied in the preceding autumn ‘or early winter. • As the subsoil requires lime just as much as the surface soil, the most satisfactory way to apply the material would be to broadcast over the land, before ploughing (usually in the autumn), half of the quantity decided upon, harrow the ploughing once to permit of the traversing of the distributor, broadcast the additional lime, on the ploughing and work in somewhat by a stroke of the tine harrow.. When this land comes to be worked up for a subsequent crop the tillage operations will distribute well through the soil the lime that has not been washed in. Top-dressing grass land with lime a commendable practice —is best done in the autumn or early winter, for the same reason as above mentioned.

The old method of applying lime is to cart out the shell lime (burnt-rock . fragmentsthe purest form of burnt lime purchasable), place this, in small heaps and cover with a layer of earth. After the heaps have remained for a few weeks and have slaked to a powder, the lime is spread in all directions with a shovel. This, of course, entails a lot of labour. The modern method is to make use of a lime-distributor, ground burnt lime or pulverized limestone being used according to the conditions already described. There . are various excellent distributors on the market. The “ star-feed ” design, an excellent type of machine for distributing lime .in a finely divided condition, is represented by machines manufactured by P. and D. Duncan, and Cooper and Duncan, Christchurch;., and by Reid and Gray, Dunedin. Other excellent

machines of this class for distributing fine lime, are the “ Ideal ” (John Knight, Albany, Auckland, agent), and the distributors manufactured by Jack and Sons, Scotland (Booth, Macdonald, and Co., Christchurch, agents), and by the Massey-Harris Company. x The distributors manufactured by the Armour, Johnston Company and by Messrs. Storrie, both of Invercargill, are also reported to be highly satisfactory. Then there are machines on the New Zealand market - that have been found more or less suitable for both fine lime and lime containing smallish semi-hard or hard lumps the condition in which naturally ground limestone is sometimes found. . These machines are the American Seeding Company’s distributor (Mason,

Struthers, and Co., Christchurch, agents) ; the International Harvester Company's Hoosier No. 2 machine, and their Low-spread farmyard - manure distributor; and the Wallace lime and manure distributor (handles fine and lump lime well, but requires a calm atmosphere). Manson.and Barr, Palmerston North, and the Canterbury Farmers’ Co-operative Association, Christchurch, are the agents for the last-named distributor. Practically all these machines have been used in the setting-up of experiments and all have been proved satisfactory for the form or forms of lime enumerated. It may also be mentioned that there is every reason to believe that before long there will be available a machine that will crush soft lump lime and distribute it in one operation.

Should a lime-distributor be beyond the reach of any farmer the material (finely divided) can be applied with an ordinary drill with coulters removed, but several drillings will require to be made to distribute the required quantity. ■ CONCLUSION. It has been shown that lime judiciously used is an excellent material provided by natural processes for the improvement of agricultural lands and for rendering them > productive or more fully so. Lime is a great instrument of production in the hands of a wise tiller. of the soil; and in these days of national stress, when production from the soil should be promoted by all possible means, the intelligent free use of this soil amendment by our farmers is highly desirable. The soils of the humid sections of the country particularly should as far as possible be made the subject of this stronger-liming campaign.