RUAKURA EXPERIMENTS.

Sun (Christchurch), Volume I, Issue 253, 28 November 1914, Page 2

RUAKURA EXPERIMENTS.

MANURIAL REQUIREMENTS.

Two years is but a short time —altogether too short—to deal with a soil in the matter of its manurial requirements. The experiments carried put by the writer during the past two years at Farm of Instruction are to some extent tentative only, and yet they are sufficiently conclusive to form a guide for future work. An experimenter, if he wishes to succeed, must lay aside all bias, scientific and otherwise. In fact, he must ignore to some extent the cast-iron teachings of both practice and science, and be prepared to experiment on lines that will nt times provoke the ridicule of both the scientist and the purely practical man.

After all, how much do we really know of soil science? And how ignorant we still are of many of the laws that determine a soil'a fertility or, as it is tersely put by one.of the most famous agricultural scientists of the present day, "between conclusions and suppositions, between what is old and what is new, between what is sought to be found out and what is already found out, there appears to be no little confusion.'' - For many years the belief obtained that it was possible determine the manurial requirements of.a plant by the aid of an analysis of the plant itself. Experience, however, teaches us that there seems to be little connection between the two; and even soil-analysis is not infallible "as a guide to successful manuring. In attempting to study the soil from a purely scientific standpoint, the layman is confronted with the fact that scientists are more at variance on this subject than on any other connected with agriculture. As an instance, among others,. I might mention the legume-nodule-bacteria theory. Somo scientists maintain that bacteria. having the power to fix atmospheric nitrogen exist in the active stage of legume nodules while others maintain that such a theory has no foundation in fact, and have even demonstrated by experiment that an increase of nitrogen has been found in soil in which had been grown a legunie. crop wliose roots carried no nodules. They also maintain that an artificial culture made from legume nodules in their active stage is valueless for inoculation purposes, as they contain no bacteria whatever until the process of decay sets in* -when, as in all decaying matter, they are in abundance. The writer has carried out Several experiments these'•• ..cultures; and has closely followed upl experiinents_carried out in other parts of the world. In

no instance has clear evidence offered that the artificial culture is of any value for inoculation purposes. My object in citing the above is not by any means to discredit the work of the scientist, but merely to emphasise what I have already stated —i.e., that the experimenter, if desirous of any degree of success iu a comparatively short space of time, must lay bias aside completely and beware of dogmatising. He will, of course, be immeasurably assisted by an intimate knowledge of the science of chemistry, l»otanv, etc.—in fact, by all sciences that mav be applied in the treatment of soils;' but he must above all things be a keen observer, and he will possibly in the meantime have more success in soil-treatment through macroscopic rather than microscopic observation, because many of the results achieved by the latter are as yet too conflicting to be accepted as reliable guides, whatever thev may be in the future. Although the value of the microscope is incalculable, and no real progress could be made in its absence, yet an eminent scientist freely admits that under very high powers of the microscope occasional explanations are given that may be the result of an optical illusion. 4 It is well, at the same time, to recognise that science does not admit impossibilities, and the future may be pregnant with great scientific discoveries; also that the highest practice cannot be other than scientific —the two are inseparable—although what is termed scientific may be occasionally unpractical.

NITBOGEN

The writer has always contended that, generally speaking, New Zealand soils contain abundance of this ingredient, and that a little care in rotation cropping is sufficient to ensure a continued, supply. Experiments at this station all tend to prove this. ' In last year's swede experiments, for instance, the plots fertilised with phosphates and potash gave a considerably greater yield than those to which a complete manure (containing nitrate of soda) was applied. The same plots are this season growing a crop of oats, unmanured, and depending on the residue of the manures, left by , the swede crop. So far as the eye can. judge at present, the same results will be obtained from the oats as from the .swedes, viz., the plots that received a complete manuring for the swede crop will again be .behind those that received phosphoric acid and potash only. This result is . doubly conclusive from the fact that not only did the oat crop receive no manure of any kind, but the swedes, roots and tops, were carted off and consumed on another field, thus doing., away with all known means of renewing the supply of nitrogen in the soil. lam quite convinced that the leaveß of swedes assimilate atmospheric nitrogen, and that on many soils they are of the utmost value when ploughed under. When a soil is lacking in nitrogen the swede leaves will to some extent renew the supply; but in this instance the tops were carted off, and yet there is evidence at the present moment that the soil still contains a great reserve of nitrogen. The history of this field, as, shown by the field gives no evidence of the application, at; any time, of a highly 'nitrogenous manure, such as nitrate of soda or sulphate of ammonia. Two years ago "the field was cropped with mangels, all of which were carted off as in the case of the swedes. The question, then, naturally arises: How is the supply \of ' nitrogen* maintained under the circumstances? Is it not possible that the soil has some other means of keeping up the supply that has liotyei been brought[sp light? :; Nitrogenous manures in the forms of sulphate of ammonia, nitrate of soda, and nitrolim have beipn applied to every description, of Crop grown at this station during the past two years without ap* parent result." It is but reasonable to conclude that New Zealand farmers should be very careful in the application of highly nitrogenous manures. They are extremely costly in any ease, and more so when they are applied to soils which do not require them.

PHOSPHOBIC ACID. The uniformly good results obtained from the application to this soil "of phosphoric acid, particularly in the form of basic slag and guanos, obviate the necessity of making any lengthy statement 4sn the matter. One fact stands out very clearly, viz., that comparatively insoluble manures, such as basic slag and some of the guanos, are as readily assimilated by ;the plant as the more soluble manures, such as superphosphates, provided the grinding or division of the particles has been sufficiently fine. This fact has bedn brought to light by practical experiment years ago, and acted on by.practical men in the face of, scientific teaching to the contrary. «For years the scientific camp was divided on this matter, and the unbelievers —most eminent scientists —were reluctantly convinced .after a seven years' dispute, which was called "the battle of the phosphates." One of the most prominent research associations in Britain, after, many years of experimental work carried out with the utmost care, has not only proved that comparatively insoluble manures are as easily assimilated as the more soluble, but also explains how this comes about. It is stated that there is an aperture at the extremity of the root-hairs, and by this means the plant assimilates the less soluble manures, provided, as stated above, that the division is fine enough. It matters little whether this explanation is accepted or not, because the fact still remains that so-called "insoluble" manures arc readily available, and during the past two years it has been one of the most outstanding results of the experimental work at this station. In Scotland, in particular, the less soluble phosphate is superseding the soluble, which means a very considerable yearly saving to the farmer.

At this station some of the best results have been obtained from slag and guano, applied separately and together, without the'addition of potash and nitrogen; and a mixture of Seychelles Island guano and basic slag has invariably been used with excellent results in the cultivation of lucerne. This seems to be particularly suitable for the soil here, and it is unfortunate that there is none how available in New Zealand, it havirig been bought 'up "by an outside syndicate.

Last season Maiden Island guano alone gave the highest yield of swedes; and 1 this season, among various manures and mixtures, the Seychelles Island: variety is giving the best results on the rape crop, even better than superphosphate and bone'dust, although the manure-merchant is .brought to see the desirability of grinding bones as finely as the highest-grade basic slag, bone manure will become almost invaluable. It has also been abundantly proved at this station, and over the whole agricultural world, that the continued application of the more soluble, and hence more acid, phosphates stinnilates many of the plant fungoid diseases, such as

"club-root," in swedes, turnips, rape, etc.

At the Moumalfaki Experimental Farm the writer carried out experiments with separate dressings of basic slag, basic superphosphate, and superphosphates on a number of varieties of swedes, and also on rape and kale. These experiments proved conclusively that the application of superphosphate greatly increased the percentage of roots affected with "clubroot," while the roots in the basicslag plot were almost exempt from that disease. SO far as this station is concerned, phosphoric acid must be the main ingredient iu all manurial applications, and a similar conclusion may safely be applied to New Zealand soils generally. POTASH. So far, comparatively little result, good or bad, has been obtained from the application of potash at Ruakura, except in the case of the potato and mangel crops, which make some response to an application of this.ingredient. In some instances, also, there has been a slight in the weight of oat straw as a result of a slight dressing of kainit.

This ingredient has been applied in various forms, such as kainit, sulphate, muriate, and nitrate, and there are now in being very extensive experiments, which will be reported on later. So far, the evidence available seems to prove that the average soil at this farm contains at present a sufficiency of available potash majority of farm crops. LIME. AH experiments prove that although lime may not be accepted as a direct plant-food, yet where it is not present in the soil in sufficient quantity other manures are, to a great extent, applied in vain. Hence it may be accepted as one of th main essentials in successful manuring.

The experiments at this station seem to prove that*- particularly on the raw and apparently-more sterile parts of the farm, an application of lime, together with draining, is all that is required to bring such soil into a profitable state of cultivation, and that manures allied previously to the application of lime were to a considerable extent wasted. A paddock of the foregoing description was sown with clovers and a little- timothy eighteen" months ago, and manured with" basic slag—scwt per acre. As an experiment, a strip right across the field was further dressed with carbonate of lime —1 ton per acre. The result is most pronounced. Where the dressing consisted of slag only, sorrel predominates; but where lime was added, there is a fine stand of clovers which, can be clearly seen from a considerable, distance. '

This experiment should also dp something to dispel; the fallacious idea' that basie slag contains sufficient lime to correct the acidity in very, acid soils, stich" as that under discussion.

On thevother- hand, .lime applied tjo comparatively poor, but higher, land had no apparent Tesult, while on the richer low now in high condition, it has been applied with: the very best results.' ', >.- K-. "•••• r•'■ '■'■:

in all districts where freight is not an obstacle, lime should be applied in the carbonate; f because of its less, exhausting nature Vas compared with burnediiihe.

Some ; farmers i-njake the mistake of applying, gypsum with the object of correcting acidity, when, correctly speaking, gypsum contains no lime, as the calcium is in combination with sulphuric/ acid, and is thus sxllphate of lime. Indeed, the application of gypr sum has the effect of increasing, instead 7 of the:soil acidity. :At the Pen tion experiments with carbonate versus burned lime were.; carried;-? out for twenty successive years (1882-1901), and the reports state that,"".with every product a greater total yield had been obtained from the plots treated with carbonate 'of lime ' than from those treated with burned lime. Furthermore, with every product whose total yield for the last eight years was greater than the total yield for the first eight years the carbonate produced a greater -increase than the burned limej and-with whose total yield for the, last eight years was less than the total yield for the first eight years the decrease was less where carbonate was usedthanwhere burned lime wft's" applied (bat strawalone excepted). This is more significant in thafe : it demonstrates the. tendency of burned lime with continued use to exhaust or destroy the fertility of the soil." There is a tendency in New Zealand at the present day to resort to liming on a more extensive scale, which is in every way commendable. It is, however, a procedure, which should be carried out with the greatest care, and, in the writer's opinion, carbonate only should be used. %he machinery as yet in use for grinding the limestone is very crude. Much better results would undoubtedly be had if the material were supplied in a finer state of division.

SULPHUR. The Eesearch Association, at Aberdeen, Scotland, which has at its head one of the ablest agricultural scientists of the present day, claims to have reduced the number of minerals essential to plants to five, by the exclusion of sulphur, and chlorine. Other very eminent scientists maintain that sulphur is an' essential element in plant and animal nutrition.

Whether it be a plant-food or not matters very little. The fact remains that it has been applied to various crops at this station during the past two years with very marked effect. Perhaps the least-looked-for and the most remarkable result is on pasture, a small area of which was top-dressed with sulphur —lewt per acre — a year ago. The herbage on the topdressed portion is now much improved, and the colour changed to a rich dark green, so much so that the effect can be seen clearly from a considerable distance. Moss, which was previously prevalent, has been eradicated.

In the rape experiments two rows received no manure of any kind, while the adjoining two rows received sulphur only, with the result that the latter are growing quite 50 per cent, more than the unman'tired' rows. This result is all the more remarkable from the fact that the field where the experiments are in being is perhaps one of the poorest on the farm. .These experiments were inspected by a prominent New Zealand scientist, who expressed himself as "astonished at the result.'' ' ' ' ' It is trusted, however, that no farmer who reads this article will run away with the idea that all he has to do is to apply sulphur and the result will be abundant 'crops.- It; is not the intention to convey ■this impression, but the results of the few experiments carried out at this station and at similar stations in. other parts, of ithe world warrant further trials of this 1 ingredient. It may not' be a plant-food, but it creates in the soil an environment suitable for plant-life. Sulphate of iron has also been applied to pasture land at this station with very marked .results. I It was my. intention to deal with the

results obtained from grcjen-manuring^ and the growing of tap-rooted plants, b«t the article is already too long, and these subiects may well form the theme for other articles.--Primrose McConnell, manager of the Buakura Farm of Instruction.