ARTIFICIAL FERTILIZERS.

Bay of Plenty Times, Volume LII, Issue 8616, 13 June 1924, Page 2 (Supplement)

ARTIFICIAL FERTILIZERS.

A CONTRIBUTED ARTICLE ON THE NEEDS Ob TAURANGA SOILS.

A ccnsidertion cf the needs of the soil of any district in tho shai>c cf what ax's known as manufactured or artificial fertilizers, immediately brings us up against; the fact that excluding lime, which is used largely as a mechanical agent in. affecting the processes c-f change which are 'distantly taking place, ami not strictly as a plant, food, there are only three elements which the farmer requires to purchase, 'ihe elements are nitrogen, potassium, and phosphoric acid. The purpose of this article is mainly to treat of those manures of which the phosphoric acid is the principal ingredient for the reason that nature has been mere niggardly in the distribution of this element through the s' il than she has of the ether mineral dement, potash, which, although as known by analysis, is not as plentiful in the Tauranga soils as in most parts of New Zealand, is present in all soils, in much greater quantity than is phosphoric acid. The amount of potash in the soil also, remain* a mora constant factor than does the amount of phosphoric acid, as larger amounts aro retained by the stems and roots, which arc not removed from tho farm to the extent that the grain is. The loss of potash however, is greater when a root crop is removed, which seldom occurs in this district. Potash, as will be : shown on another occasion, is net generally plentiful in sandv soils, wlv h artdeficient in the day part-cles of which potash i* a constituent. In the case of stock husbandly, also, the amount) of phosphoric acid removed in the carcase is greater than the amount of potash, which, having fulfilled its function in building up the animal economy, is mostly avoided in tho dung and urine, especially the latter. In regard to nitrogenous feitilizers, it is generally recognised now that given a good rainfall and a soil in which leguminous plants thrive, 4hc purchase of such manures is not good fanning -economy. Assuming then, that we need phosphatic or phosphoric acid manures, which are one and the same thing, wo have to remember that whether we. buy superphosphate, ground Nauru reek, or basic slag, wo arc buying only on 1 lie phosphoric acid value cf the stuff in the bags, and nothing more. If we buy pure uiuiwnea--wo l>uy wltll the phosphoric acid about three per cent cf nitrogen, but as a rule, bones are now: steamed or boiled before being crushed for farm use, and in the process most of the nitrogen is extracted, so that as a rule, bouedust is classed as a source of phosphoric acid only. But although all the above manures are bought cn tho unit value of the one element which they contain, their value as a fertilizer varies greatly acording to the soil and climate of the district in which they are to be used. Phosphatic manures are classed as either acid, such as superphosphates, or basic, also called neutral, such as slag, Nauru, or bouedust. In practice it has been found that super, owing to its watersoluble phosphoric content, is better suited to » district where (he rainfall is low, mainly it is thought, because it enables the young plant to get quickly away during the short period of seasonal rain, and thus ' gives it an extended root action, which enables it to take advantage of the reserves of water in the deeper layers cf the soil during the dry season which follows. Such is the theory governing the use of super in South Australia, where, in some of the wheat growing areas with, a fifteen inch rainfall, it has been found that fifty pounds of super to the acre is sufficient, whereas the use of neutral manures, needing as they do, a. moist climate and soil, are not regarded with favour in *uch a dry climate as South Australia. Although nearly the whole of the phosphoric acid in super is soluble in water 1 , owing to its combination with sulphuric acid, that condition does not exist for Icng, because the super tends to enter into close association with the mineral ingredients in the soil and rapidly reverts, that is, returns to a mote or less insoluble condition. In the making of super, the phosphate cf lime- is mixed, by different makers according to the nature cf the phosphates, and the formula according to which the proportions necessary arc worked out, with from 50 to 80 per cent of ite weigh! of sulphuric acid, which enters into combination with two parts of lime cut of three of which tire phosphatic lime was originally composed, leaving (lie other moiety of lime and the phosphoric acid united, in which condition the latter is water .soluble. ,But phosphoric, acid has an objection to ihe one moiety of lime base, and immediately proceeds to enter into union with the lime in tlm toil, until presently it is combined with two parts of lime and is net so soluble as when originally applied, but is readily acted cn by the acids furnished by ihe roots of plants. Super' is made out of hones, Nauru fock, or any other rock phosphates. Basie slag is a result cf mixing lime With iron during the process of steel making. The phosphates in the iron ore is an. impurity which has to be got rid of before good steel can be made, and as phosphorus has an affinity for lime, it

cut era imc combination with the latter in the furnace, and with r.-tbcT mineral dross is run out. 1 of the furnace in a mol ten rendition, and is afterwards ground to a standard degree c f fineness, when it is availaide for use- without- any further preparation. Slag, in addition to the phosphate of lime, contains as much as ten per cent of free lime, that is, lime not- in combination, up to twenty per cent of c-sides of iron, besides small quantities of matrneeia. sidphur, and cither minerals. The phosphoric acid in the slag is not soluble in water, hut is easily dissolved by a weak sclution cf citric arid of a strength which is estimated as equal to that cf the carbonic acid excreted by tha rents of plants. Consequently, slag is a manure, which, although not as quick acting as super, is readily available to the plant, as a top-dressing, provided that it is used in a moist- climate and is sown early enough in the year to allow of th" r- tion of the acids in the soil moisture having full play. Blag is not. so well suite] to a low rainfall district as is super, but on the c th yr hand a-'ts; better than super rn a soil deficient in lime. Although the value ,-.f slag as a fertilizer lias been known since- 1885, the exact, assoication of its constituent parts is not yet understood, nor the reason why the phosphoric acid that it contains is mere readily soluble than other untreated forms cf phosphate of lime. Whatever the combination is, the icsnltant effects aie such as to- cause it to be greatly appreciated by those farmers for whoso operations it is suited, especially by stock keepers. In addition to its action ns a manure- for grasses am] crops, sing is regarded as playing a pait in maintaining t he health of slock which arc fed ou fodder grown by its aid, in addition to which, i( has a remarkable effect in stimulating the growth of legumes, rape dally of while clover, I tuts helping to increase (he quantity of nitrates available for the finer grasses. So great j s its stimulating ellect mi clover, that farmers in bnglaiid when slag was first used, noting (his, declared Ural the- seed must he in the- slag. The writer has known farmers to ecudomn the use of slag for this very reason, on the ground (hat the abnormal growth of the- cloven smothoroff th« liiiv-i- •■'grasses'. The mistake wap apparent- in subsequent years, when (he grases, nourished by the plenti--1 tide cf nitrates rendered available, by the bacteria which made their homes on iho roots of the clover, reasserted fhemscl ves. Blag, being a neutral manure, may be safely used continuously in large quantities, without- any fear that it will exercise a deleterious effect on the mt'i'hanical condition, or texture of the soil, or that it will be the means of promoting the growth of any but the finer: grases. Super, on the other hand, is said ta injuriously affect the condition cf seme- soils by causing the particles to or run together, if used continuously. It has been noted in the case of very light soils, that slag gives quicker results in those- parts of the ground that are naturally damp and peaty, but that is due largely to- the fact; that the moisture is present in sufficient volume to bring about the- solution cf the phosphoric, acid. Th© presence of the- pe-at, or humus, in such places, is, however, the main cause of the successful results of using slag, as the carbonic acid gas, and to some extent the humic acid present as a result of the decay of vegetable- material, is abscutely necessary in cider to promc-le the conditions neecssary to enable the soil water to attack and dissolve the otherwise insoluble phosphoric acid. Such a condition may be- brought about in almost any soil if the rainfall be present, by bringing about a fine stale- of tilth, and by green manuring. The statement so freely made, that Taurauga soils an in the nature of a sieve, and (hat anything applied to the land is quickly washed down, can only be made by the theughiess and ignorant. All phosphatie manures have the capacity of entering into combination with the other elements present in iho* soil, and in course of time, were not the dissolving agents present, we should have phosphates of alumina, inm, potassium, etc., as well as the insoluble phosphate of lime which would form as a result of the phosphoric acid in super entering into combination with other moieties of lime in the soil. Blag, by the way, owing it is thought, to the abnormal combination brought about bv its association with limo under the influence ef great heat, does not so readily seek union with further limo bases. Hence the phosphoric acid, having entered into combination with ether mineral bases, can lie more be washed down than the soil itself can, because it becomes part of the soil. These remarks do not apply to nitrogenous manures. Anyway, water only sinks through the soil to the point of saturation, and it reaches that point by percolation as through a filter, and there most of it remains, a rc so voir for the use of the plant in the dry time. There ate exceptions, but I am writing of circumstances a.,* I believe them to exist here. When the need arises the water in the lower reaches of the soil rises

Another so nice of phosphoric acid is (lie unaltered guano obtained I nun the is!an Is ■. 'T the. -o.isl < f . lAuai ansi other places -where the ■sliinato i.s comparatively rainless. These guanos contain up to sixty per cent of phosphoric acid, a large annum, of which is soluble, besides a fair amount, of nitrogen. .Having < x plained tlie various sources of phosphoric acid, it is necessary to sc? the exact reason why we use it, be~ c'uiss although v. e km. w that wi get better crops, better pasture, and as a result better milk cheques, we do- net quite understand too manner in which it acts. Hus is no place for a disquisition on the part which phosphoric acid plays as a constituent of the hods which we cut, and which we obtain fu n the soil, but wc are concerned with the manner in which phosphoric acts as part of mechanism of the soil in its action mi plant Hlc. Even on a soil naturally rich in this element it, lias been found that so small an application ns fifty pounds of super to the acre ensures a good take and subsequently a good crop, for the reason that the immediate solubility of the super promotes the root action of the seedling turnip and enables the fibrous mots to reach deeper into the ground, where they have the benefit cl the film water, and the plant feed held in suspension therein. Furthermore, phosphoric has the effect on grain crops c.f hastening the ripening process, and of increasig the proportion of grain to straw. Phosphoric add again in conjunction with lime enters info combination with other bases in the sr.il, and although tending to become inM'lublc by Mich action, until released by further processes, has the effect of rendering available a moiety of the element a portion of which it has displaced, so we got phosphates c.f iron, alumina, potash, etc. Again, in some cases, it is the dominating factor in promoting growth, because although we are accustomed to use, say, 2 cwt of slag, containing ,'sGlb of pin spin iic ■■■■• ill per acre in growing swedes, and little or no nitrogen, wc find that, analysis of tlie resultant: emp shows it to contain cue hundred ami fifty pounds of nitrogen, one hundred and twenty cf potash, and only tliiity of phosphoric acid, ycl every fanner knows that without the slag there would have been but a poor

to the surface by capillary alt taolu.>l, reaily for the use of 100 plant. But, it may be said, the phosphoric acid in solution will go down into the water. Not so, because-, except in the case of newly applied water-soluble super, which condition in super does net- last long, as 1 have already explained, the phosphoric arid is not in a state of so-lu-tion, and is only slowly mad; so as and when required by the plant, through the* action cf the acids secreted by its roots in conjunction with the acids formed by decaying organic matter. The plant obtains all its water from the soil; a well prepared soil, by reason cf the fineness cf its particles, increases the watei of capillarity, and renders more certain the supply cf plant food as well as water in a dry’ season. The next great source of phosphoric acid is one of the various preparations cf beno, as bonedust, strnmed or raw, or the mixtuie known as blcod and bone, which ci ntains a comparatively small proportion cf plicsporic acid and a relatively large amount cf nitrogen, and is therefore, a costly manure to buy ,as nitrogen is not required on a well farmed soil, although perhaps necessary cn a raw, hitherto uncultivated ground, such as some of our fern country. Bcnes may contain up to sixty per cent cf phosphate of lime or the equivalent of from twenty to thirty pet cent, of phosphoric acid. Bone is comparatively’ slow acting, that is not readily soluble, alhough for top-dressing pasture it is looker! cu as one of the best, the results cf a heavy dressing of bones being apparent for many years, although the first effect may net be apparent till the second year after using. Bones at' largely used in the manufr.dure of super. The third great supply of phosphoric acid, and the one which will become increasingly important to us, both as a material for the manufacture of super and for use in a raw, finely ground slate, is Nauru rock. Like 1 all the phospltides which we use, except bass' slag, Nauru is of organic or animal origin, being derived from (lie droppings and remains of seabirds and live fragments of their fishfood, which from long contact with the coral reek has absorbed the carbonate. of lime necessary to change it from the puiely animal guano into the present form of trkalcic phosphato rock. Nauru is richer in phoshuri;' acid than any other maerial sold for farm uso containing by guaranteed analysis, about eighty-two per cent of trkalcic phosphate, whereas a good sample of bonedust contains fifty per cent, a»<t. slag forlty per cent, but bonedust contains a percentage < 1 nitrogen not found in slag, and perhaps only to a small amount in Nauru.

cm]). The question of the relative values cf different, classes cf phosphatic manures depends, beyond (hr quant it v and availability of the phosphoric avid, on (hr suitability of (hr particular form of phosphate fm the sojl and climato which we have fcc.i d&al witli- A sandy or petty soil with such a rainfall at litis district possesses, where the * riginal lime content ; f the soil is

not -U.u, is. in tin- long run. uu-H ii benefit tod by the application <'f 1 neutral manures, partly because ot t their action in assisting the nitrate ‘ form ins hartuia ami partly bceaus.’ ] hr in- nuu-acid, do not s> readily J ttn.i tu lax-erne lucked up with cth- 1 i: 1, js soluble has. s. ami a'so b?- * cause- the rainfall provides sufficient < moisture in 1 he s ii to bring about ■ solubility. On the ether hand, super had a bad HTcct on soils m -t • to woil u.pplh d with Ume. as the 1 sliirht , xe s'- of free arid in the sup- i a . converts part < f the carbonate of lime in the soil into gypsum, ' otherwise sulphate of lime. In luvhm phosphaiic manure we have to rcniemh:: that suiter is the. only one in which part of the phosphors’ aci-d is soluble in water and that p.r. I s'on • liters inio assoeiatiou -with t.rlur bases and becomes insoluh'o in time, but in such an extremely hue state as to be readily available- as a plant food, and that slag, though not soluble' in water is ic.uiiiv soluble in the r. 'I. luring next to super in that, respect. All mattres are sold on the unit basis, that, is if you buy slag at five pounds a ton and it contains Twenty per cent phosphoric, it costs you five shillings a unit or twenty two pounds and a half bo tin- ton, roughlv, that would give four hundred and forty eight pounds of phosphoric in a ton of slag, the balance being lime, iron and some other stuff. Always calculate the unit vahte of the phosphoric acid, it is quite easy, and then you won't runaway with the idea that the other man's slag is the cheapest because he is selling it at four pounds a ton. ft niav be only twelve per cent stuff, in which case ii would be costing you six shillings and eight pence a unit. Alsu don't forget, whether you buy otic kind of phosphate or another < f the sanm Hass, the cue with the largest, aimamt of phosphoric acid given the same pric,- per unit is always the cheapest to buy, because you get a concentrated artich with less bulk, which, mens less carting, and loss lifting. Titus one ton td manure containing twenty per rent of phosphoric aeid at' live pounds a ten, is equivalent to two tons of ten per com stuff at fifty shillings a ton. When von open vmir bag of manure yon will find there a copy of a guarantor.l analysis as required tin- Fertilizers Act. This will (HI you that lire bag contains so much per cent of phosphoric acid or phosphoric auhvdricle', which for your purpose is the same tiling, and in lb. - next column you will read that ii a lso contains so: much (rlcalcic phosphate. Well, the tricalcic phosphate! is simply the previously expressed amount, of phosphoric aeid combined with the- amount of lime f. r which it has a natural af-

Unity, ;iml th p. povtimi should be found by multiplying bv 2. IS win a eighteen p’i cni: phcspheri,- will iqual a bn IU; ; c than thirty-nine por c.'iu ( f tricaleic phosphate. The gieat trouble with farmers buying manure is t bar they buy cn!y for to lay aml <!.■ not trouble about the future. Fifty years ago the English farmer used ground bones which are slew acting, and did n, give inti'll return for two years but the lasting cffV.'ts were apparent in the pasture for many years. In later times, a dressing, <T half-a-hm of slag was a common tiling, but the effect was lasting. There is no reason why fine ground Naum rock should not have the same permanent effect as bones, both become slowly soluble, in the soil and there is no comparison in price <:n the unit value. Nauru containing (igiiiy-twe. per cent cf phosphite of iime, equal to say, thirty-seven per cent of phosphoric acid, is a far cheaper manure fc; top-dressing permanent pastures at live pounds a ton, than is boiiodnst containing twenty three prr cent phosphoric at ten pounds a ton. In this case the Nauru would costtwo shillings and eight pence, a unit, while the honednst would cost oighit shillings and eight pence fer a unit, that means at those pi ices, that yon get three and a quarter times as much for your money if you buy Nauru instead of hones. Nauru has given good results in the Wellington province and should do so here. It may not show much result for a year cr two but it remains in the soil, and if tfhc latter i.-. in good condition, tlie Nauru will be available as plant food for many years to o.mE. Fanners as a rule do net use sufficient mamne, , end fin not sow it eatly enough, basic manures sut'h as bones, slag, - nr Nauru should be put on as a tc.p- , dressing early in the autumn. They . do net wash away, cr sink out of reach ; experiments all Ibdliam--1 stead extending over many years, have proved that all the pliosplnns ie acid used, after allowance had - been made for the amounts known to be removed in the crop, remains cd in the top nine inches of (lie soil, r and special traps at the drain outfalls proved that none was being - carried down to a depth- Kuper i may he used in the spring, but f should only be used as a starter for 1 a .’rep of young grass, but not for ,j top-dressing permanent pastures. I- Used for the latter purpose emtlinur onsly it is apt in prove a curse < n r sandy soils and is one of the agents t favouring the spread of disease in o turnips. Farmers in this conntiy c Spread out their manure 100 . tjiiu < (c get. good results, fifty acres well •, conditioned and manured will give f belter results than a hundred puor- - ly worked and lightly mamued.