FACTS FOR FARMERS. POWER OF SOILS TO ABSORB FERTILIZING SALTS.

Waikato Times, Volume III, Issue 109, 16 January 1873, Page 2

FACTS FOR FARMERS. POWER OF SOILS TO ABSORB FERTILIZING SALTS.

I (From Liobig's Modern Agrk.ti.turk.) I We have hitherto believed that plants received their food from a bolution, and that the- rapidity of its effect was in diiect proportion to its solubility. We have supposed the active elements to be earned in solution in ram water and I caibouio acid to their routs, and have regarded thorn in the ! light of bponges, half in the moist giuund and half in the 1 an 1 , continuously absorbing V>y their roots the water which ; evapoiated fioiu their leaves. Whatever was in solution | passed with the water into the roots, and by the process of nututiou was appropriated by the plant. Tho hull and the plant weic both passive- in the operation. ; Vegetable physiology has taught us that an element of food vi the liOil at a durance from the rootlets of plants is available as nourishment, prouded theie is water between the rootlets aiul the food to dissolve the latter. In consequence of the ev*poiation from the leaves, the rootlets I suck the water, which thus, with the substances dissolved in it, receive a movement onwards towards them. We j believe that the water w.is the earlier of the moat remote elements of tho boil to the immediate presence of the 1 plant. | If 4000 lbs of gram and 10,000 lbs of itraw require 100 1 lbs of potash and 50 lbs of phosphoiic acid for their develop1 ment, and if a heekue of ground contain these quantities m a soluble a\ ailable foi m, then there \\ ill be siiflieient for this crop. If the same field contain double or a hundred 1 times as much, then we should expect two or a hundred ! crops. This lias been the physiological doctrine. ; But all this has been a gieat mistake. We have inferred I fiom the efteet of water and cat bonus acid on rocks a simii larity of action on soils : but this conclusion is false. There is not to- be fonnd in chemist) y a more wonderful phenomenon— ono which more confoundb all human wisilem j — than 19 presented by the soil of a gaiden or Held. I By the simplest experiment any one may satisfy himself that ram water iilteied through fielder gai den soil does not dissolve out a trace of potosh, silicic acid, ammonia, or phosphoric acid. The soil does not gvvo up the water one particle of the food of plants which it contains. The most continuous lain cannot remove from tho field, except meclumically, any of the essential constituents, of its feitility. The soil not only retains Jirmly all the food of plants which is actually in it, but its power to pioscrve all that may bo useful to them extends much further. If rain or other water holding in solution ammonia, potash, phosphoric and silicic acid be biought in contact with the soil, these substances disappear almost immediately fioin the Bolution — the soil withdraws them from the water. Only such substances are completely witluhawn by the soil as. are indispensable articles of food for plants ; all others remain wholly or in part m solution. If a funnel be filled with soil, and a dilute solution of silicate of potash be- poured upon it, there will not be found in the filtered water a trace of potash, and, only under certain circumstances, silicic aokl. If freshly precipitated phosphate of lime ov phosphate of magnesia be dissolved in wator saturated with carbonic ucid, ( and filtered in like manner through soil, there will not he found a trace of phosphoric- acid m tho filtered water. A solution of phosphate of limo in dilute- sulphuric acid, or of. phosphate of magnesia and tumnoMin in carbonic- neid water, comports itself in the s>«mim> manner The phoiphorio acid of the phosphate of limo and the phosphoric acid and ammonia of the magnesia salt rom un m tho sod. Charcoal ro-aets m a similar manner with ninny soluble salts; it removes colouring matter and salU from solutions. It i 9 natural to. look upon tho effect m both eases as proceeding from tho same cause. In the cose of chaicoal it is a chemical attraction, which proceeds from its surfuuc , but the constituents of tho sod take part in irs action, and lieuec it must m many caeca bo dill'crcnt from that of chnrconl. Potash and sjxla are well-known to stand to eneh other in the closest ohomieal relation, and o\en tlieu salts ha\c manj properties in common. Chloride of potnsstium, for example, has the same mstnlme form us ohloridc of sodium ; and in taste and solubility they differ hut slightly An unpractised eye can scarcely distinguish thorn, but tho sod can do this in tho most perfect manner. If we add any soil in powder to a dilute nolnt ion of chloride of potawium, in a short time there will not bo found any potassium in solution Thosmnoqunntit) of earth do< ••, not withdraw from a solution of chloride of wdium containing an equal amount of chlorine even the half of the sodium ; consequently complete decomposition takes place with the potassium, but only in part with the sodium. I'oU-jli is found in all our land plant-, but soda forms only un exceptional constituent of their allies. From sulphate and mtiatc oi soda the soil withdraws only a part of the sodn, but the whole of the potash troin the corresponding potash smalts Experiments expressly made for Una purpose lui\o shown

that 1 litrc=loUo cubic centimes (=(il cubic inches Enjj) of garden sail rich in lime will take up the- potash (Vom 2 »23 cub cent. (==l23 (5 cub inches or 3} pints) of a solution of silicate of potush, winch contains m every 1000 cub. cent. 278 grammes (—( — 13 gr-* ) of silicic a.eul and 1*166 grammes (—lB grs ) of potash. Prom these, data we can onloulato that a field of a hectaro (---2J acres) in extent, and having a depth of a i of a metro (—lO inched nearly) of soil of the •nine kind as that used in the experiments would withdraw from a similar solution more than 10,000 lb-<. of potash, and retain them for the use of plants. A similar experiment, made with a solution of phosphate of magnesia and ammonia in carbonic- acid water, ■bowed that a 2 } acre field would withdraw 5000 lbs. of this salt from such a solution. A loam (poor in lime) produces thp same effect. These facts give us some conception of tho powerful action of soils, and of the strength of their attraction for three of the chief elements of tho food of our ottlthatcd. plants which in consequence of their solubility in pure and carbonic acid wnlor could not be retained in the so* did the latter not possess this power of attraction. These experiments are so simple and easily performed, that they may be exhibited at lectures. In filtering, care must be taken that the fluid does not form canals, which would prercut the complete contact of the solutions with the soil. Very dilute solution* of siHcnte of potash, chloride of potassium, k&, must therefore, be u-cd in the proportions, for example, of one part of substance to 500 of valor. Saturated solutions of tho other substances, such as phosphate of lime in carbonic acid, may be employed. Gcncralh in the first portion of fiUurc from the phosphate* of lime not a trace of phosphoric acid can be detected by molybdate of ammonia. A solution of silicate of potnslij which re-acts distinctly alkaline with turmeric paper, instantly loses this re-action by simple mixture w ith sod. This power of absorption in soils for ammonia was obscned by Thompson, and for phosphoric acid and some potns'i salt by War, so long ago as 1850 ; but up to that time neither vegetable physiologists nor scientific agriculturists had taken notice of the remarkable discoveries of tho-e English clio nNts, so pregnant with important results to phj siology and agriculture. From stale urine, liquid manure diluted with much water, or from a solution of guano, soil, when used in sufficient quanli'y> removes the whole of the ammonia, potash, and phosphoric acid which they contain. Not a trace of these substances can be found m tho water which ilows from the soil (Thomson, Huxtiblc-, Way.) I cannot here omit a circumstance communicated to me a few years ago by Dr Marquart, of Bonn, and which illustrates in a remarkable enough nmniier the power of absorption of clays for ammonia: — A manufacturer on t'le Rhine conceived the idea o£ extri cting, hy means of ammonir, the oxide- of copper which was found as malachite and nzuro spur dispersed tbrougk shale. The experiment had succeeded with him on a small scale. At a considerable expense he constructed a large extraction apparatus, consisting of two boilers connected by a very wide tube. The fluid ammonia was placed in one boiler ; the tube was filled with the shale; and the second boiler served as condonser. By this arrangement it w asintended that the ammonia and vapour of water should be condensed in the tubs, and after dissolving the oxide of copper, pass over into the second boiler, and made ogam to extract the copper from the fresh shale. As the whole apparatus was hermetically closed, it was hoped that the same quantity of ammonia would ser\e without loss to extract large quantities of shale. The boilers were employed alternately as condensers. The first trial •« as so far successful that a solution of oxide of copper reaily collected in one of the- bwlers. But on passing the ammonia through a second portion or shale, it disappeared ia a manner most incomprehensible to the manufacturer. The proee-s in consequence had to be abandoned. 'I he disappearance of the ammonia in this operation was undoubtedly due to the absorbent power of the clay of the shale. This fact may bo taken a 9 a proof of the powerful attraction existing between these two substances, which apparently could not be overcome even bj the influence of a high temperature. The power possessed by soils to withdraw ammonia, potash, phosporic and silicic acids from solutions is limited. Each soil is endowed with its own peculiar capacity in this respect. When brought in contact with these different I solutions the soil becomes saturated with the dissolved limllor, and the [excess of soluble substance then remains m solution, and can be detected by the ordinary reagent, A sandy soil absorbs less than tho same volume of a marly soil j and the Lit ter loss than a clay soil. The variations in the quantity of matter ab«orbcd are as great as the difference evicting among the soils. We know that no two iro alike ; mid it is not improbable that certain peculiarities m culrnation stand in certain relation to the unequal pow or of different soils for absorbing one of tho atone substances. It is not impossible that, by a closer stud\ of | thm relation, we mnv iirme at n qn to new and unexpected , means of juifgmg of the agricultural value or fertility of our fields The act ion of a soil rich in organic matter and the solutions fibo\onientioned is worthy of remark. A cla % \ or limo soil poor in orgnniY matter withdraws all the potash and silicic acid from a solution of 6itimte of potash ; whereas one rich in Ho-cilled humus extracts, the potash, but lea\ea tho silicic I acid in Rolution. This comportment involuntarily recalls j the net ion of dortu ing vegetable remains in tho soil on the growth of plants, which, like reeds and hor«e tails, require a large quantity of silicic avid. These plants abound in socalled sour, moor, nud moadow lands ; but disappear from them on the application of lime,, and give place- to others better fitted for fodder Fxpenments sbow that the same garden or forest soil, rich in ]mmv«," whioh withdraws no silicic acid from a solution of silicate of potash, iminmediatoly acquires tho j power to do so if it be mixed with a little slated lime before the silicate is added to it, Both constituents,, potash and silicic acid, are then retained by the soil.