THE APPLICATION OF LIME.

Otago Witness, Issue 2437, 28 November 1900, Page 4

THE APPLICATION OF LIME.

Farmers of arable lands in Great Britain, compelled by necessity to purchase fertilisers largely, have long been aware that of the plant foods requisite — nitrogen, phosphate, potash, and lime — it is the substance which is in least quantity that rules the crop, and that one substance cannot supply the place of another, so, therefore, if there is a deficiency of any one of the ingredients, it matters not how much the others may be in excess, they cannot take the place of the one that should be there. "The strength of a chain is its weakest link," and likewise the strength of a soil is measured by the minimum quantitj r present of any one of the essential ingredients of plant food. Thus, there may be sufficient nitrogen, phosphate, and potash but a lack of lime, and tlie crop may fail on that account. That is, the lime may be the minimum quantity, and it is the 'minimum quantity of any one ingredient that controls the result. But apart from its essential as a plant food, lime has a powerful influence in promoting the physical and bacteriological changes, in the soil conducive to increased fertility. Until recently carse land (strong clay) farmers in Scotland had a strong prejudice in favour of applying heavy dressings of six or seven tons per acre of slacked lime on ac-' county of its , disintegrating and ameliorating influence on the physical condition of heavy clay soils. -But the practice has been abandoned, "because it didn't pay." "It ■was calculated that four tons per acre of lime applied -to land would exercise beneficial action for 18 years, but for very heavy clay soils six or seven tons would be requisite for the purpose. With depression in prices of farm products arose the expediency of judicious economical expenditure, and, as regards manures, such as would assure certain and quick returns. The heavy liming system fell into disuse, and was succeeded by the almost universal practice of applying the mineral in small quantities and oftener. According to the experiments of Lawes and Gilbert there is an annual loss of lime from the soil per imperial acre of about scwt, removed by crops, stock, and drainage water, but, a*s well-informed farmers in the Home country have long known, when it is nej cessary to apply lime it has to be applied iii excessive quantities — in amounts much ! greater than those the plants and drainage i withdraw from the soil — "since lime is not only added to the soil because it is a necessary plant food, but on account of its value as an indirect manure, and for many other reasons." We quote from a standard essay on "Economy in the of Artificial Fertilisers." When the farmers in Great Britain, or at least the considerable number of them, well read in agricuii tural scientific literature, had been convinced by incontestable evidence — most of which wa? got on their own farms and under their own supervision — that if an I abundance of one essential element of j)lant food is forthcoming, and others equally necessary occur in inadequate amount only, tlie more active growth engendered by the plentiful constituent will unavoidably create a, heas^ demand ujgon the soil's reserve

stores of those less freely supplied, they readily perceived that heavy dressings ot lime are distinctly disadvantageous. Well read farmers know that "a soil to be fertile must be germ occupied — that is, a sterile soil is an unfertile soil," and they know further that lime applied very much in excess cannot but have the ell'ect of destroying a great deal of bacterial life in the soil. Some years ago, it was stated in a report of the experiments conducted j at the Heading Extension College, England, that "in no case has lime given anything like a profitable return." The result was not at all surprising, for a dose of three tons of caustic lime per acre had been applied to pastures, and must have ha^c the I effect of destroying much of the beneficial j germ life in fi;e surface cS'-i. The report goes on to say that "in most cases basic slag has given the results generally attributed to lime at a much less cost. ' But was that not due to the fact that basic slag contains 20 per cent, of free lime, and the lime applied in this way is in a quantity much better suited to the wants ol the soil bacteria than a three-ton dose - oi' caustic lime? In regard to finger-and-toe being most prevalent act soil which is de"ficient in lime, the report states that '"any form of lime — hot lime, chalk, or gas lime — thoroughly, mixed with the surface soil, will .do much to check the disease." Commenting on this ■statement, the N. B. Agriculturist says:" — "As a matter of fact the experience throughout Scotland is thai neither -chalk nor gas lime is at all comparable with ground hot lime as a means of destroying the disea&e-germ, and in no case should the amount of lime applied exceed two tons per acre. A dressing of ocAvt to 4cAvt ot kainit (a pota&h manure) will be found very useful to apply at the time of seeding." The peculiarity of the Dalmeny experi- j ments lies in the principle upon which they are conducted, Avhich is claimed to differ substantially from that commonly pursued. The guiding principle in these experiments has from the outset been'that which is making itself known as the new soil science. In other Avords, the experimenters have proceded on the assumption — noAV universally accepted as correct — that the fertility of a soil is dependent upon the presence and activity of bacterial life, and that no matter how lavishly manure is applied, the absence or suspended action of the nitrifying organisms can not be atoned for. The soil that is not occupied by soil bacteria they hold to be infertile. Starting Avith these advanced ideas as their guiding light, therefore, Messrs Hunter and Drysdale haA'O conducted their experiments upon a new basis, inasmuch as they have pursued the indirect but economicar*method of maniuing to pormoie the increase and activity of the nitrifying organisms. It "h ould be difficult to say how far this line of procedure h?s led the A~erdicts away from what are obtained at other experimental stations, or what the ordinary 3xperimentation would have obtained upon the sain© land, but it is pretty safe to assume, having regard to the vital part played in ■ the fertilising of the soil by soil bacteria, that the system which takes due cognisance of their presence and j Avork is the one likely to produce the most ! economical results. The practical bearings of this teaching are obvious as, for example, when Mr Hunter pointed out to the assemblage of farmers who inspected the Dalmeny farms in August last that on account of the nitrogen-storing power possessed by their nodule bacteria, the leguminous plants did not require any artificial nitrogen to be applied to them, so that a small dressing of lime, together Avith phosphates and potash, was all that Avas required to ensure a first-class crop of beans, peas, vetches, clovers, etc. Regarding Avhat Mr Hunter had said, as to the groAving of leguminous crops and the necessity j for analysing manures, 'a leading farmer present mentioned ft notable fact — namely, that up till a few years ago a "Special Bean Manure" 'had been largely sold in the Carse of Stirling at £11 per ton, and as j that manure gave A T ery excellent results, no purchaser ever thought of having it ana- ( lysed or of grumbling at the price, until' one farmer of a scientific turn had it analysed, Avhen it Avas found that the manure consisted of kainit to the extent of 50 per cent, the balance being lime and' coprolites, while the actual value of the manure as determined by the Highland .Society's scale of values was only £3 per ton. The results of the scientific research work and. farm ' management at Dalmeny are entitled to the exceptional consideration by farmers in this colony which they have obtained in the Home country. In his address to the visitors in August he explained Avhy this should be so. The experimental station, he said, "was primarily founded for the purpose of finding out the best method of producing the best possible .crop at the loAvest possible cost. These experiments had been conducted on neAv lines — namely, on the lines of the new soil science. They had seen the results that day, not only' on the experimental grounds, but also on the Home farms, for, as a matter of fact, the Avhole of these tAA'o large farms Avere treated as an experimental station, the system that gaA r e the best results on the "experimental grounds being carried out all aver the farms. . . , The experimenters held firmly by the opinions which they had proved to be founded on fact ; but, Avhile j they held firmly by these opinions, they aA'oided the very appearance of forcing their opinions on others. There AA r ere some also Avho had asked in a very sarcastic Avay Avhy the Dalmeny experimenters had never published an official report of their experiments. To that he would reply that they avouM publish a full official report in j due time, and meantime they could slioav Ansitors what Avas much better than official figures and official reports — namely, crops such as, he was safe to say, they would not find the better of in any part of the 'country. . . . They aimed at showing lioav to farm well and profitably, and they did not endeavour to slioav, as some noted experimenters had done, that 10 tons of, ! farmyard manure per acre gave "better result^ than 20 tons ; that gorse Avas the best food of all for feeding sheep on ; or that you could groAv Avhite crops continuously on the same land for 50 years without pro-

It must be borne in mind that on the Dalmeny farms, there is an application of from 4ewt to 6c\vt of ground caustic lime per acre in the preparation of the soil for all crops, — white or green, — in the rotation; so, therefore, there is so -frequent a repetition of the dressings as must beneficially affect the physical condition of the soil, while giving prompt and better returns from the crops grown. "Looked at from the point of view of common sense, does it not seem, injudicious to commit many hundredweights per acre of lime to the land in the expectation that the soil will take charge of it, and only part with it in small quantities as each succeeding crop requires it? Such may be what a farmer would desire, but the state of things is very different in practice." When manure is applied to a crop the plants take up what they require, or" what they can lay hold of, but the excess beyond requirements may suffer a variety of fates. Some will assume a form in the soil that plants can do little with, and much will escape into the drains or subsoil. The Dalmeny system of applying small dressings annually to every crop in the rotation has been shown to be not only more economical but attended with markedly better results than the old-time plan of excessive applications. The superiority of caustic lime over slaked lime (calcium hydrate) as a dressing' has been incontestably established, and of greater importance still, farmers have been taught the lesson that by the adoption of the Dalmeny system, whichever of the limes mentioned they may use, they can efficiently fertilise two to- two and-a-half acres for -a less expenditure of money and labour than has been previously incurred in dressing an acre. One hindrance to the use of caustic lime out here is that there are no grinding appliances attached to lime kilns in the colony. The obviation- of this difficulty must rest with farmers themselves. Should a pronounced demand arise for ground caustic .lime, owners of kilns will find it to their interests to meet marked re r Quireroents. In the meantime ingenious farmers are likely to find means of crushing down the material received from the kilns so that it may be distributed evenly in comparatively small quantity, and with the view to avoid slaking, Avhich very much impairs its potency.