The Journal of Agriculture.

New Zealand Journal of Agriculture, Volume VII, Issue 1, 15 July 1913, Page 1

The Journal of Agriculture.

Volume VII, - No I>

WELLINGTON, N. Z., 15TH JULY, 1913.

Price Sixpence.

PHOSPHATES:

THEIR IMPORTANCE TO NEW ZEALAND FARMERS.

B. C. Aston,

F. I.c.

Introduction. - . OF the many factors upon which successful farming in New Zealand depends there are some which may be included under the term management/ capable of being varied by the individual to his own advantage; there are others which may be referred to under “climate” and “prices,” and which are beyond his power to alter.

As to management, proper selection of plants and animals may greatly aid the farmer in his journey to the goal of success, but of all the factors contributing to this happy end the manuring of his land is the one which— all things into consideration—is easiest to control, and therefore one which should merit his most careful thought and action.

Let-us take an imaginary case, which may better explain what it is sought to convey. Assuming that the soil is of average fertility, the season favourable, the tillage adequate, labour not more scarce than usual, prices satisfactory, and the farmer wise in his management with one exceptionthe manuring; every link in the chain is complete and strong save this one. This may be faulty through sin of ’ omission or of commission : no fertilizer, the wrong one, too little of the right one, or lastly, but rarely, too much of the right one* are errors. In all probability the immediate saving through neglect of this matter has been but a few shillings per acre, an amount insignificant compared with the sum of the other charges for labour, rent or interest, seeding; &c. The net loss through not getting a full crop, however, is out of all proportion. If in a favourable season the measure of a farmer’s success may be much diminished by so simple a means, in an unfavourable season how much greater will be the extent of his failure ! Essential Valuable Plant-foods. The fertilizer enactments of different countries recognize three essential plant-foods as being .of sufficient importance to legislate about, these, in the descending order of their relative cost, being (1) nitrogen, (2) potassium, (3) phosphorus. I shall refer to these in future under the more familiar terms “ nitrogen,” “ potash,” and “ phosphates.”! You will observe that no mention is made of calcium (the metal of " which . lime is the oxide), iron, sulphur, magnesium, and other undoubted essential plant-foods. These are

' i part of nitrogen is equivalent to 1-214 parts of ammonia; 1 part of phosphoric anhydride is equivalent to 2-183 parts of tricalcic phosphate ; 1 part of potash is equivalent to 1-85 parts of sulphate of potash. These are the terms allowed to be used by the New Zealand Fertilizers Act, and on the purchase of any parcel of over 5 cwt. of fertilizer the farmer is entitled to demand from the vendor an invoice certificate stating the percentage of plantfood present under these headings. To the farmer wishing to inquire further into the matter the following instructions will be helpful.

usually present in sufficient amounts in average soil, for average crops. They are, moreover, intrinsically of far lower value than the three first mentioned. Of these three, nitrogen—the most expensive—is used either in its insoluble and less expensive form, as the organic portion of bonedust, as dried blood, or as meat-works offal. The soluble nitrogenous fertilizers, such as nitrate of soda, sulphate of ammonia, cyanamide, and nitrate of lime, are usually in New Zealand applied only to special crops, such as potato, mangel, and garden crops. Potash manures come to us almost exclusively from Germany, derived from the great Stassfurt mineral deposits. Potash enters very sparingly into proprietary mixtures for general crops, and although it is used more largely for special potash-loving crops, still in minor quantity compared to phosphates. The comparatively small quantity of nitrogen and potash imported into New Zealand is significant.

In Australia, for the last year of which we have information, 1910, there were imported of purely phosphatic fertilizers 205,489 tons, while of other fertilizers 18,866 tons were imported. Similarly, in New Zealand the purely phosphatic fertilizer imports for the year ending 31st March, 1913, 'were 87,411 tons, while of other fertilizers there were 12,190 tons. Nitrogen and potash, are evidently in the minority. With regard to nitrogen, however, it must be remembered that both Australia and New Zealand are producers of a certain amount of organic nitrogenous manures in the shape of meat-works offal, which is used locally. No potash fertilizers, however, are locally produced.

To convert nitrogen into ammonia multiply the amount by 1-214. Conversely, to convert ammonia into nitrogen, multiply by 0-824. In this way the following table may be used : ■ ■ Nitrogen N X 1-214 = Ammonia ». ■ . NH 3 . Nitrogen N 2 • X 4-705 = Sulphate of ammonia (NH 4 ) 2 SO 4 . Ammonia NH 3 X 0-824 = Nitrogen N. . Sulphate of ammonia (NH 4 ) 2 SO 4 X 0-212 = Nitrogen . N 2 . Phosphorus 2P X 2-289 = Phosphoric anhydride PO 5 . Phosphorus 2P X 4 - 975 = Tricalcic phosphate Ca 3 P a O 8 . Phosphoric anhydride P 2 O 5 X 0-437 = Phosphorus 2P. Phosphoric anhydride P 2 O 5 - x 2-183 = Tricalcic phosphate Ca 3 P 2 O 8 . Tricalcic phosphate Ca 3 P 2 O 8 X 0-201 = Phosphorus 2P. Tricalcic phosphate Ca 3 P 2 O 8 x 0-458 = Phosphoric anhydride P 2 O 5 . Potassium K 2 X 2-228 = Sulphate of potash K 2 SO 4 . Potassium K 2 X 1-204 Potash K 2 O. Potassium K X 1-906 = Chloride (muriate) of potash KCI. Potash K 2 O X 0-830 = Potassium K 2 . Potash K 2 O X 1-850 == Sulphate of potash K 2 SO 4 . Potash K 2 O X 1-582 = Chloride of potash 2KCI. Sulphate of potash K 2 SO 4 x 0-540 = Potash K 2 O. Sulphate of potash K 2 SO 4 X 0-449 Potassium K 2 . Chloride of potash KCI X 0-525 = Potassium K. Chloride of potash 2KCI X 0-632 = Potash K 2 O. -■

. It is interesting to follow the fate of certain elements in the soil. Nitrogen is readily leached out of the soil by rain, and is lost in large amounts. Calcium and sodium are also washed out of the soil in large quantities, but potassium and phosphorus are lost only in very small. quantities. Phosphorus becomes • less availablethat is, more insolubleand is abstracted by the crops and stock grown on a given farm. • By these means phosphorus is lost, but not through leaching. The manufacture of nitrogenous manures from the inert nitrogen of the atmosphere is already an accomplished commercial success, which relieves us of the haunting fear that the exhaustion of the Chilian deposits of sodium nitrate will mean diminution of the world's wheat-growing capacity. That Australia is so large a consumer of phosphates to the exclusion of nitrogenous manures may seem remarkable when it is remembered that nitrogen is the dominant ingredient required by wheat in Europe. It has been found that on the Australian wheat-soils nitrogen is unnecessary, or even harmful— result no doubt due to the difference in soil and . climate between Europe and Australia, which indicates how important it is that every country should elaborate- its ' own system of agriculture, and not follow blindly the methods of other countries practised under entirely different conditions. ' .' Perhaps Phosphates only needed. . F. W.. Clarke, - the great authority on geo-chemistry, computes the amount of potassium in the ' lithosphere (the solid earth) as 2-45 per cent., and the nitrogen in the lithosphere and ocean together as only 0-02 per cent, (but the atmosphere we know is four-fifths nitrogen). The phosphorus he estimates as only o-n per cent, of the lithosphere. It is highly desirable that the principles of manuring advocated by Dr. Hopkins, of the Illinois University, should be given a fair trial in New Zealand. Briefly, his advice is to rely on greenmanuring and the growth of leguminous crops to supply the nitrogen needed," which they abstract from the atmosphere, and to liberate potash from the inert soil-silicates by appropriate and economical methods, ' and thus render available the potash required. . This disposes of the two most expensive plant-foods, the nitrogen costing from three to four times and the potash about twice the price per unit that phosphoric acid does. There now remains to consider how this last food can best be supplied. The American idea is to use the cheapest known form of phosphate of —that is,

ground rock phosphate —in the finest powder possible, and to apply it in conjunction with ground limestone if necessary.

N.B.—The monetary values are given in pounds sterling and decimal parts of The values are those declared at the Customs; the farmer pays at least /i per ton more. • . '

Some very interesting facts may be learned from the above statement. It would appear from first sight that superphosphate is the form of phosphate which is imported in the largest quantity, but this is found to be untrue when the compositions of the respective fertilizers are compared. Remembering that the superphosphate and the basic slag average 18 per cent., the bonedust 22 per cent., and the guano 27 per cent, of phosphoric acid, it is seen that the kind of phosphate most largely imported is that in phosphate rock or guano, which is practically the same thing. Superphosphate, however, comes a good second, bonedust third, and basic slag last. Basic slag* is, however, showing signs of rapidly advancing in public favour, for during the last four years the figures representing its

importation have been going up with leaps and bounds. All the import figures show good increases from year to year, except those for, bonedust, an exception which I am very glad to see. The importation of bonedust shows a steady decline since 1910, coincident with an increase in the declared value. Farmers appear to be recognizing that they can pay too much for a good thing,. and there is no doubt that other phosphates are taking the place once occupied by bonedust. I have a strong suspicion that for years the value of bonedust has been overrated. Absence of adequate field experiments renders it necessary to emphasize the fact that this statement is a suspicion merely, which needs proof. Another feature worth noting is the constancy in the declared values of the phosphates other than bonedust throughout the quinquennium under review.*

Sources of Phosphate. The phosphates used in the fertilizer trade are obtained from many countries. Owing to the increased demands for phosphate several deposits have been either worked out or operations have been limited to the supply of .rock to specified areas. This has stimulated search for new fields and has resulted in the discovery of several important finds. To those who carp at scientific expeditions the instance of the important deposit at Christmas Island, discovered by the “ Challenger ”, expedition, may be cited. Our own Otago mines are now turning out 8,000 tons of marketable phosphate yearly. Phosphate may possibly be discovered in other parts of the Dominion, and should be looked for in limestone districts. Isolated fragments of phosphate have been found at Whangarei and at Kaikoura.f' , . •

Some twenty-odd years. ago the world’s total production of phosphate was less than a million tons a year, but in 1908 Voss estimated the production as follows : Tons. America .. . . 2,300, 000 Africa .A .. . . 1,544,000 France .. .. .. 350,000 Belgium .. ‘ .. .. 150,000 West Indies .. .. .. 30,000 Pacific islands . .. .. .. 350,000 Russia, Norway, &c. .. .. 100,000 Total .. ... 4,824,000 We have thus a fivefold increase in twenty years. In New Zealand in 1901 only some 33,000 tons, .which we may be sure was mostly phosphate, were imported; in 1912. 100,000 tons were imported, a threefold increase in consumption in twelve years. In many European countries the consumption of phosphate has recently doubled, and if it were not for the newly discovered deposits in Africa, America, and the Pacific agriculture would be in a sad position for want of fertilizers. America is now using about four and a half-million tons of fertilizers, and its Government is prohibiting the export of phosphates from the fields found in Government territory. Other countries may follow suit, and even prohibit the export of phosphate entirely. The phosphate used in New Zealand comes largely from Pacific sources, even the • Japanese superphosphate having its origin in the Pacific. Ocean and Nauru Islands are estimated to contain fifty million tons of phosphate rock. With an output of, say, its present production (263,000 tons) it will be exhausted in two hundred yfears. It seems probable, however, that what will happen is that the output will be tremendously increased l and that the life of two hundred years may be very much curtailed.

How TO EXPERIMENT WITH PHOSPHATES. In conclusion, some practical advice may be given as to the broad lines upon which experiments in the field .with fertilizers should proceed. In any series of experiments on New Zealand soils it will always be advisable to apply lime in conjunction with the phosphate in one experiment at least. The amount of available lime in the soil has a great influence on the efficacy of the phosphates and the amount it is necessary to apply. The forms of lime best suited to the different, soils must be studied as carefully as are the forms of phosphate applied.

A saving in freight, cartage, and bags should be attempted by purchasing concentrated fertilizers and diluting them down with material such as sand, dry earth, or ground limestone, obtained on the farm. I recently had to pay £3 per ton for forty miles cartage of fertilizer which only contained 40 per cent, of phosphate of lime, costing £4 per ton. If the concentrated superphosphate, which is obtainable in Auckland at £9 12s. per ton, containing 96 per cent, phosphate, could have been applied it would have resulted in a saving of nearly £2 per ton on the cartage and freight alone, and yet the farmer would have received the same amount of phosphate.

Another important point is the mixing of one. phosphate with another. Farmers are aware of the excellent mixture they can obtain by mixing bonedust with superphosphate, the bonedust with its coarser particles reducing the floury superphosphate to a state that will easily run through the drill. Bonedust has the further advantage that it does not react with the superphosphate . when it is in bulk, and the mixture may stand for some days without any conspicuous change taking place. The high price of bonedust is, however, .making, and rightly so, the farmer look somewhat askance at its use.

The mixing of basic slag and superphosphate is condemned by some authorities. These, I think, should be disregarded until experiments in New Zealand have decided the matter fully. Certain difficulties attend the application of the mixture. Some farmers have had considerable success with it, others largely, I fear, through not following directions — failed. Trials should be made with two. parts of slag and one of superphosphate, and also with equal quantities of each. The mixture should be sown as soon as mixed, and not more should be mixed at a time than can be expeditiously dealt with. If chemical action commences. to take place and hinders the free running of the mixture, inert material must be mixed in to dilute the constituents.

In top-dressing grass lands it has become usual to apply potash fertilizers in conjunction with slag. Some of these potash mixtures contain large quantities of sodium chloride (common salt) and magnesium salts. Kainit, for instance, only contains some 12 per cent, of potash, whereas sulphate of potash contains over 50 per cent. What one would like to see thoroughly tested is whether potash, sodium chloride, and magnesium salts are necessary individually and collectively, and if they are, whether they could not be purchased separately more advantageously than they are now, and mixed as required.

* See article on the use and abuse of artificial fertilizers: N.Z. Journal of Agriculture, Vol. iii, p. 464.

f The different ways in which plant-foods may be spoken of is a severe stumblingblock to the farmer, unlearned in chemical terms, who would comprehend something of the art of manuring. The simplest method of referring to the three foods mentioned is that in which the amount of each element is quoted thus—nitrogen, potassium, and phosphorus. Under other systems nitrogen may be quoted in terms of ammonia or sulphate of ammonia ; potassium in terms of potash (dipotassic oxide) or sulphate of potash ; phosphorus in terms of phosphoric anhydride or tricalcic phosphate. It is important for the New Zealand farmer to realize that- —

* The American farmer can purchase ground phosphate rock at from one-fourth to one-fifth the price per unit which a New Zealand farmer would be charged.

For a full account of basic slag, which every farmer should read, see articles in the Journal, Vols. iv and v, pp. 454 and 25, or Bulletin No. 26, to be had gratis on application.

. * A matter which often arises in the lay mind is the discrepancy between the unit value of phosphoric acid in guano compared with that in bonedust, superphosphate, and basic slag. - Here we have- a guano containing 27 per cent, phosphoric acid declared at £2 65., while a bonedust containing 22 per cent, is declared at £6 45., a superphosphate containing 18 per cent, at £3 75., and a slag containing 18 per cent, at £3 35., per ton. The chemist’s refuge under the fire of this sort of question is to say , that unlike things cannot be compared. Bonedust contains a quantity of nitrogenous organic matter which doubtless, by its ready decomposition in a warm soil, renders the calcium phosphate more available ; superphosphate has had the original phosphate of the rock phosphate, from which it is chiefly made, so altered by sulphuric acid (vitriol) that it is soluble in water, and hence diffuses into the soil and is there precipitated in a very finely disseminated state, much finer than could be got by any mechanical means. Basic slag contains its phosphate in combination with lime and silica ; there is also a large proportion of iron silicate and free lime present', which may have some effect on the availability of the phosphate. There is only one way to obtain an adequate reply to the question of what phosphate is cheapest to use, and that is to put the question to the soil itself. Field or pot experiments alone can answer certain questions, but the experiments must be so conducted as to ensure absolute confidence in their accuracy.

f Those interested in the matter should consult the writer’s Bulletin No. 1, “ Phosphate in New Zealand.” ..

Phosphate Importations. Year ended 31st March. Bonedust. Superphosphate. Tons. ■ Value (Gross). Value per Ton. Tons. , Value (Gross). Value per Ton. £ £ £ £ 1909 .. 9,143 52,4 2 I 5’7 21,910 80,774 3’7 1910 12,177 66,361 5’4 25,228 91,926 3-7 1911 .. II,058 61,893 5'6 27,442 99,477 3’6 1912 10,799 69,032 6-4 32,567 H9,597 3’7 1913 9,143 12,177 11,058 10,799 9,281 £ 52,421 66,361 61,893 69,032 60,050 £ . 5:7 5’4 5'6 6-4 6-4 21,910 25,228 27,442 32,567 32,964 £ 80,774 91,926 99,477 H9,597 120, 303 £ 3’7 3’7 3'6 3'7 3’7 Basic Slag. Guano and Rock Phosphate. Year ended 31st March. ■ , . Basic Slag. Guano and Rock Phosphate. Value Tons. Value per . Value Value Value (Gross). Value per Ton. Tons. Value (Gross). Value per Ton. £ £ £ £ 1909 4,321 14,595 3’4 12,030 38,626 3’2 1910 .7 5,013 16,126 3'2 6,088 15,578 2-6 1911 .. . . 8,670 28,231 3’3 15,963 42,164 2’7 1912 .. 16,227 53,067 3'3 22,050 6l,622 2’8 1913 4,321 5,013 8,670 16,227 20,133 £ 14,595 16,126 28,231 53,067 66,389 £ 3’4 3’2 3'3 3’3 3’3 12,030 6,088 15,963 22,050 25,033 £ . 38,626 15,578 42,164 61,622 65,084 £ 3’2 2'6 2-7 2-8 z 2-6

Let us now see how we attack this problem in New Zealand. The following table shows the phosphate importations in New Zealand for the last five years :-