AGRICULTURAL CHEMISTRY AND VEGETABLEPHYSIOLOGY.ALTHOUGH for the year 1914 no results of exceptional importallcehave to be recorded, a number of investigations of considerableinterest relating to soils and plant nutrition have been carried out.The soil problems which have received most attention are thoseconnected with partial sterilisation, absorption of bases, acidity,and the production and movements of nitrates in soils, whilst inthe case of plant nutrition a good deal of attention continues tobe given to the question of stimulants.A t the meeting of the International Commission on the ChemicalAnalysis of Soils, which was held in Munich in Apri1,l the subjectsdiscussed included: (1) the preparation of soil extracts f o r totalanalysis; (2) the estimation of readily soluble soil constituents ;and (3) the estimation of soil acidity.On the assumption that the double silicates in soils belong totwo sharply defined groups, those of the one group readily givingup their bases when treated with a 10 per cent.solution of anelectrolyte, whilst those of the other group, representing the un-weathered rock, are acted on very slowly, a provisional methodhas been devised in which the soil is treated with 10 per cent.ammonium nitrate solution. It was found that the main portionof the bases which dissolvo at all was contained in the first 50 C.C.of the filtrate.It was, however, decided, for obtaining a standard method, toconfine attention for the present to extraction with water contain-ing carbon di.oxide.Of the publications which have appeared during the year maybe mentioned : “ Erniihrungsphysiologisches Praktikum derhoheren Pflanzen,” by V.Grafe ; ‘ I Die Typen der Bodenbildung,”by A. Glinka ; ‘‘ Grundziige der Pflanzenerniihrungslehre undDiingerlehre,” by W. Kleberger; a third edition of Tollens’“ Kurzes Lehrbuch der Kohlenhydrate,” and a third edition ofWahnschaff e’s “ Wissenschaftliche Bodenuntemuchung.”1 Il’ature, 1914, 93, 598.21214 ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.The A trnosphere.A useful series of analyses of rain-water has been made inSouth Africa: extending over one or two years in the case ofGrahamstown, Kokstad, Bloemfontein, Durban and Cedara, andfor shorter periods at several other places. It is shown that a tGrahamstown and Kokstad the total nitrogen, as ammonia andnitrates, amounts to only 1-88 and '2.00 kilos.per hectare perannum, which is about half the amount found a t Rothamsted.The difference is mainly in the ammonia-nitrogen, which atGrahamstown amounts to only 1-06 kilos., and at Kokstad t o 1.25kilos., per hectare. At the other places much higher results wereobtained, the total nitrogen varying from 5-47 t o 6.98 kilos. perhectare, owing perhaps, in part, to contamination with dust, etc.,especially in the northern parts of the Union, where dust stormsare very frequent. The high results are all due to much largerproportions of ammonia, especially a t Cedara (5.28 kilos.), wherethe nitric nitrogen is quite iiormal (0.97 kilo.per hectare). Theanalyses include chlorides, and in some cases sulphates as well.An important investigation of rain collected in towns has beenundertaken by the Committee for the Investigation of AtmosphericPollution,3 which has already published some monthly resultsobtained a t a number of towns. All the samples are collected ingauges of a standard type, and a standard method is employedfor analysing the rain and other deposits, so as to obtain com-parable results.The series of analyses of rain commenced some years ago a tOttawa4 are being continued, and some analyses of rain and snowhave been made during a few months at Mount Vernon, Iowa?Soils.Acidity in soils is generally t o be attributed t o the decomposi-tion of organic matter under unfavourable conditions, or to anexcessive employment on non-calcareous soils of salts of which thebases are mainly utilised by plants.Instances have also occurredof acidity brought about by the oxidation of iron sulphide.Recent experiments in Japan have shown that acidity occursin certain sandy soils containing only small amounts of humus, andthat this mineral acidity is due to aluminium and iron compoundsC. F. Juritz, Smth African J. Sci., 1914, 10, 170 ; A . , i, 916.Lancet, 1914, ii, 1010, 1110.F. T. Shutt, Exper. Farms Rep., 1914, 265.G. H. Wiesner, Chem. Arms, 1914, 109, 8 5 ; A . , i, 472.ti G. Daikuhara, Bull. Imp. Centr. Agric. Exper. Stat. Japan, 1914, 2, 1 ;A., i, 1211AGRICULTURAL CHEMISTRY AND VEGETABLE PHYSIOLOGY.215absorbed by soil colloids. It was found that the application ofammonium sulphate, disodium hydrogen phosphate, and potassiumchloride t o a granit'mandy soil resulted in a reduction of the smallyield of barley, obtained in the unmanured soil, t o almost nothing;whilst with a further addition of calcium carbonate the yield wasenormously increased. The manureld soil was so strongly acidthat the zinc pots in which the experiments were made were per-forated. Further investigation showed that the majority ofJapanese and Corean soils examined were acid, and that in a t leasthalf of them the acidity was due, in part, to colloid absorption ofaluminium and iron compounds. As regards geological origin, itis shown that soils from Mesozoic formations are the most fre-quently acid, then Tertiary, Palzozoic, and diluvium soils.A number of zeolites which were neutral to litmus became acidarter treatment with acetic acid, or extraction with a solution ofpotassium sulphate.Acid kaolins behave towards neutral saltsolutions the same as acid soils, and similar results are obtainedwith alkaline kaolins, after they have been treated with diluteacids; and with granite and other alkaline rocks which have beensubjected to the action of aqueous carbon dioxide for some weeks.Similarly, the acidity of the soils is increased by treatment withdilute acids; mineral acids and formic acid were found t o have thegreatest, and about equal, effects, whilst with acetic acid the in-crease in acidity was much' less, and with oxalic acid very much less.The filtrates from acid soils which have been treated with aneutral salt solution give with ammonia precipitates consistingchiefly of aluminium hydroxide, the amount of which correspondswith the acidity of the soil and with the amount of N-alkali usedin the titration, whilst the filtrates from neutral soils and aqueousextracts of acid soils give no precipitate.The acidity of soils after treatment with different salts variesconsiderably, according to the salt employed.With chlorides, thehighest acidity was obtaiped with potassium salts ; sodium,magnesium, and calcium chlorides produced only about half theacidity or less. Of the different potassium salts, the chloride andthe nitrate give the greatest acidity, whilst the chlorate, sulphate,and iodide gave respectively 90, 80, and 76 per cent.of the acidityproduced by the chloride, taking the averages of a number of soils.As regards the degree of acidity produced by potassium chloridesolutions of different strengths, i t was found that the acidityincreases rapidly a t first, and more slowly afterwards, as thestrength increased from N / 5 0 t o N ; in one case the maximum wasreached a t this point, whilst further slight increases were obtainedin other soils with stronger solutions216 ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.From some of the results the conclusion might be drawn thatthe acidity of mineral soils is due to kaolin or acid silicates. I nthis case, kaolins should be strongly acid, and should part witha good deal of aluminium when treated with a salt solution.Kaolins are, however, sometimes neutral, and even alkaline,whilst acid kaolins only give up small amounts of aluminium whentreated with potassium chloride.Both kaolins and soils, whentreated with aluminium and iron chloride solutions, absorb vary-ing amounts of t h e bases and become acid, or, if acid, more so.Iron absorbed in this manner is displaced by aluminium, but notaluminium by iron; the absorbed aluminium and iron are partlyredissolved by potassium chloride solution. It seems probable thatwhen neutral or alkaline soils acquire acid properties by treatmentwith acids, the aluminium o r iron compounds, produced by thaaction of acid, are absorbed by colloids and their positive ionsreplaced by the basic ions of the neutral solution.Some of the results just referred to have been obtained in anindependent investigation on adsorption,' in which it is also shownthat the acidity produced in kaolins and soils by the action ofacids is not due t o absorption of acid; soils which had been treatedwith sulphuric acid, washed with water, and extracted withpotassium nitrate solution failed to give up any further amount ofsulphuric acid.It was also found that soils which were boiledfor some time with concentrated sulphuric acid acquired the samedegree of acidity, when treated with potassium chloride solution, asanother sample which was treated with N/40-acid. I n anotherexperiment,. soils and kaolin were treated with hydrochloric acidand then with barium chloride. They were then washed, againtreated with hydrochloric acid, and the barium estimated; theamount recovered corresponded with 95 per cent.of the acid liber-ated by the soil from the barium chloride, and with 89 per cent. inthe case of kaolin.Thesoil is an old alluvium and a light loam in a good physicalcondition, but deficient in phosphoric acid and especially incalcium carbonate. Although some crops, such as Phaseolzismzcngo, will grow on the soil, most others, such as oats and grain,die as seedlings unless considerable amounts of lime are added.As a result probably of the acid conditions, the soil contains anorganic acid which, in the free state, is very toxic to Andropogotzsorghum, butl not t o all kinds of plants; it even acts as a stimulantwith paddy-rim.The results of a number of plot experiments withAnother case of soil acidity has been noticed in Assam.8J. E. Harris, J. Physical Chem., 1914, 18, 355 ; A., i, 653.9 A, A. Meggitt, Mem. Dcpt. Azric. ITtdia Chem. Ser., 1914, 3, 235 ; A . , i, 1212AGRICULTURAL CHEMISTRY AND VEGETABLE PHYSIOLOGY. 217and without lime showed that the only unlimed plots that gaveany material crops were those which received alkaline manures,and some which had superphosphate. The action of the latternianure in saving the crop, notwithstanding the increased acidity,is attributed to its stimulating action on root growth, which wouldresult in increased oxidation and in the destruction of the toxicsubstance.Acid clays and loams also occur in considerable amounts inPorto Rico,S where they have an intense red colour, due to thevery complete weathering and the breaking down of the ironsilicates to iron oxide and silica.The climatic conditions whichfavour the production of these soils are frequent rains in hotsummers, which wash out the bases, and if such conditions pre-vailed when the-clays were being produced from felspars, the baseswould be washed away, as soon as liberated, by the co-operation ofcarbon dioxide. As regards the constitution of the acid clay, thefollowing formula is suggested, as it admitx the absorption ofphosphoric acid as well as of bases:OH* Al<~>Si(OH)*O*Si(OH)<~>Al*OH.Although the subject of humus, or of those portions of i t whichdissolve in water or in alkali, continues to receive a fair amountof attention, no very definite results have been published duringthe year.The existence of humic acids seems no longer to be dis-puted; it is now rather a question of the relative importance ofhumic acids and of colloids which absorb bases, since the presenceof both is recognised.By extracting Sphagnum peat with water as long as anythingis dissolved, two distinct colloids have been obtained; and a non-colloid, which is supposed to consist mainly of Berzelius’ apocrenicacid. After subsequent extraction with 4N-ammonia until nothingremains but fibres, undecompmed wood, and a black substance, asolution is obtained which contains another acid, perhaps creriicacid.Suspensions of Sphagrmm and of Sphagnum peat behave verydifferently when treated with ammonia, the peat yielding largeamounts of salts, whilst the Sphagnum itself does not, and i t isshown that the effect on conductivity of the production of saltsfrom the peat exceeds that of adsorption even in concentrationsof 0.01N.No decomposition can very well occur, since humatesare extracted even by O.005N-ammonia solutions.The hard, brittle, insoluble modification of humic acid obtainedby heating a t looo can be rendered soluble by prolonged treatmentI) 0. Loew, Landw. Jcbhrb,, 1914, 46, 161218 ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.with alkali, and the transformation can be followed by means ofconductivity measurements.10It has been shown11 that acid peats sometimes yield as muchsoluble humus when directly treated with alkali as when previouslyextracted with acid, and that even some alkaline peats give upmore than half the total soluble humus when directly treated withalkali.Alkaline peats, when hydrolysed with 20 per cent.hydrochloricacid, yielded small amounts of ammonia, whilst in the case of acidpeat no ammonia was formed.When solutions containing equivalent amounts of ammoniumand potassium hydroxides are employed for extracting humus, itis found that ammonia extracts the larger amount of nitrogen.I n an investigation of some Hawaiian soils,12 i t was found thatthe amount of ammonia present was usually considerably in excessof the nitrates.The amounts of amide, basic, and non-basicnitrogen (probably largely, if not mainly, diamino- and monoamino-acids respectively) varied a good deal; the average amounts wereapproximately 24, 10, and 65 per cent. of the total nitrogen dis-solved by boiling h'ydrochloric acid.The nitrogen of the humus of these soils, extracted by 3 percent. sodium hydroxide, varied, the average amount being about62 per cent. of the total nitrogen. Of this, about 46 per cent. wasprecipitated by neutralising with acid, whilst an excess of acidgave a further precipitate containing about 12 per cent., so thata very considerable portion of the soluble nitrogen of these soils(42 per cent.) becomes soluble in acid after treatment with 3 percent.alkali.As regards other organic, non-humus substances present insoils,13 benzoic acid has been obtained from a subsoil (but not fromthe corresponding surface soil), and m-hydroxytoluic acid has beenfound in several soils and subsoils, but only in any quantity in thelatter. Vanillin, which had hitherto only been detected in soilsby its oldour and by some of its reactions, has now been isolatedfrom some soils in Florida.Alde'hydes have been found in a number of soils-in neutral,alkaline, and acid soils, the latter containing aldehydes more fre-quently than the others. No relation seems t o exist between thecrop being grown and the presence of aldehydes, and they are not10 S. OdBn, Kolloid Zeitsch., 1914, 14, 123; A . , i, 599; also Arkiv.R e i n . Min.Geol., 1914, 5, No. 15 ; A . , i, 1165.J. A. Hanley, J. Agric. Sei., 1914, 6, 63; A., i, 471.12 W. P. Kelley, J. Amer. Chenz. Xoc., 1914, 36, 429, 434, 438; A . , i, 368, 472.l 3 E. C. Shorey, J. Agric. Research, 1914, 1, 357; A., i, 916AGRICULTURAL CHEMISTRY AND VEGETABLE PHYSIOLOGY. 219confined to any particular locality, being found its far apart asNew York and Mississippi.Both productive and unproductive soils were found to containaldehydes; the majority of positive results were, however, obtainedwith unproductive soils.14Partial Sterilisation of Soils b y Heat and Antiseptics.A study of the effect of various antiseptics on the numbers ofbacteria in the soil, and on the production of ammonia,*5 showed.that whilst the general effect of the different substances is thesame, the amounts of the different antiseptics required to producethe same resuks vary considerably.As regards volatile anti-septics, the amounts required to produce the desired results werefound to be as follows: toluene and carbon disulphide, 0.09;benzene, less than 0.16; cyclohexane, 0-17; chloroform, 0.23 ; ethylether, 0.74; hexane, 0.86; methyl alcohol, 3'2; ethyl alcohol, 4.6per cent. of the weight of soil. The action of non-volatile sub-stances is more complex. Whilst cresol, for instance, produces thesame initial effects on the number of bacteria as toluene, its sub-sequent effects are different in several ways; the number of bacteriaincreases enormously, and the flora is very simple as compared withthat obtained when volatile antiseptics are employed.The highnumbers are, however, not maintained, but fall rapidly. Theincrease in the ammonia is much less than with toluene. Phenolgives similar, and quinol (with only 0'05 per cent.) somewhatsimilar, results, whilst pbenzoquinone, although less potent, alsobehaves similarly. Both quinol and crmol seem t o be utilised bythe surviving bacteria as food.Formaldehyde is normal in its initial behaviour, killing theprotozoa and reducing the number of bacteria; this is foilowed bya marked rise in ammonia, but no increase in bacterial numbers.Pyridine has to be applied a t the rate of 0.8 per cent., as smalleramounts are readily assimilated by the bacteria.The results obtained with the various antiseptics on tomatoesgrown in soils containing disease prganisms showed that form-aldehyde and pyridine are the most effective,; next, cresol, phenol,calcium sulphide, carbon disulphide, toluene, benzene, andpetroleum ; whilst the least effective of the substances used arethe higher homologues of benzene and naphthalene, and some oftheir derivatives. Steam proved, however, to be more effectivethan any of the substances mentioned, and in vegetation experi-ments a steamed soil should always be included as a standard.Itl4 0. Schreiner and J. J. Skinner, J. Fraxklin Inst., 1914, 178, 329 ; A . , i, 1195.l5 E. J. Russell and W. Ruddin, J. Xoc. Chem. Ind., 1913, 32, 1136; A., i, 242220 ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.must also be borne in mind that in laboratory experimentsorganisms, once killed, cannot reappear, whilst in culture experi-ments such rigid exclusion is, of course, impracticable, so that anabsolutely identical order of effectiveness of the different antisepticsis not to be expected.The results of pot experiments16 in which buckwheat, wheat rye,and barley were grown in a very pour loam which had been heatedat 9 5 O , 135", and 1 7 5 O , respectively, showed a marked accelera-tion of growth in the case of buckwheat in the soil heated a t 9 5 O ;the other plants were only slightly affected.Heating a t highertemperatures, especially a t 1 7 5 O , retarded gemination and growth.The results of other germination and vegetation experimentsmade in heated soils 17 indicated that a toxic substance is produceda t low temperatures, and in greater amount a t high temperatures,125-150O.When low temperatures are employed, the effect of thetoxin is not lasting, and the growing plant is eventually evenbenefited by the heating. The heated soils were found to containmore soluble inorganic, and especially more soluble organic, matterthan before heating. When exposed t o air, the toxic substance dis-appears, and much of the additional soluble organic matter revertsto its insoluble state. The production of a substance beneficial t oplants, which is attributed to the oxidation of the toxin, might,however, equally well be due to the oxidation of some other sub-stance present.As regards the retarding effect of heating soils on germination,it has been shown18 thst ammonia has this effect, and that heatedsoils may contain ammonia in quantities capable of producingsimilar results.I n addition to changes in the solubility of humus brought aboutby heating soils, a number of experiments have been made withHawaiian soils with reference to the changes in mineral con-stituents.19 It is found that whilst the effects of heating vary withdifferent soils, the amounts of water-soluble manganese, calcium,magnesium, phosphates and sulphates, and bicarbonates increasewlien'soils are dried a t loo0; in about half the soils, the solubilityof the potassium, aluminium, and silica increases, whilst in somethe solubility diminishes.Higher temperatures (250O) and ignitiongive similar results, the changes being sometimes greater and some-times less than those produced a t looo.Solubility in N/5-nitric acid was not altered much by heatingl6 G .W. Wilson, Bwchem. Bull., 1914, 3, 202; A., i, 644.17 Duke of Bedford and S. P. U. Pickering, J. Agric. Xci., 1914, 6, 136.18 E. J. Russell and F. R. Petherbridge, ibid., 1913, 5, 248.l9 W. P. Kelley and W. McGeorge, Hawaii Exper. Stat. B d L , 1913, 30 ;A, i, 1044AGRICULTURAL CHEMISTRY AND VEGETABLE PHYSIOLOGY. 221the soils a t looo; heating a t 250° in some cases considerably in-creased the solubility of the aluminium, manganese, potassium, andphosphoric acid, whilst calcium and magnesium became less soluble.As regards nitrogen, the usual destruction of nitrates wasobserved, and ammonia was prodaced in abnormally large amounts;there was also a loss of about one-fourth of the total nitrogen whensoils were heated a t 200O.It was observed that when soils weresubjected to the heat of brush fires, ammonification was stimulated,whilst nitrification was checked for a t least two months. Hawaiiansoils are characterised by inertness, and ploughing, followed bythorough tillage a t frequent intervals for several months, is usuallynecessary; the burning of brush without aeration seems to havesimilar effects.The action of lime in partly sterilising soils, to which referencewas made last year, has been further studied, and a number ofdefinite results relating t o the changes in the number of bacteria,ammonification, and nitrification in a variety of soils has beenobtained.20 It is shown that the amount of lime required dependson the character of the soil.A sandy soil poor in organic matterand calcium carbonate required 0.2 to 0.3 per cent., a clayey soilcontaining calcium carbonate reacted with 0-3 to 0.4 per cent.,whilst an acid, sandy soil, and a rich garden soil which containedcalcium cubonate, required from 0.5 to 1 per cent.The greatest increase in Che number of bacteria was obtainedin the acid, sandy soil. With 0.4 per cent. of lime, the numberrose from 5 to 906 millions per gram in ninety days. The highestfinal number (337 millions after 310 days) was obtained with thesGme soil treated with 1 per cent. of lime.This soil also producedthe highest amount of ammonia, 112 per million, as nitrogen, in310 days, whilst the highest amount of nitric nitrogen was foundin a humus-sandy soil, also with 1 per cent. of lime; this soilcontained 210 per million of nitric nitrogen after 380 days.The results of pot experiments in which different amounts oflime were added t o the soil accorded with the nitrification results.Results similar to these were obtained with a heavy soil con-taining calcium carbonate.21 Addition of 0-3-1 per cent. oflime resulted in a marked decrease in the number of bacteria,followed by an immense rise, whilst 5 per cent. of lime completelychecked bacterial growth. I n a calcareous loam, addition of morethan 0.05 per cent. of lime caused diminished nitrification, and onsandy soils, both rich and poor in calcium carbonate, addition ofZo H.B. Hutchinson and K. MacLennan, J. Agric. Sci., 1914, 6, 302.21 F. Miller, Zeitsch. Garmngsphys., 1914, 4, 194 ; Bull. Agric. Intell. PlantDiseases, 1914, 5, 1168222 ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.lime up to 0.1 per cent, lowered the production of nitrates fromammonium sulphate, and 0.5 per cent. inhibited nitrification.The effect of heat and of antiseptics on the catalytic power ofsoils, rate of the action of the soil on hydrogen peroxide, has beeninvestigated.22 As regards heat, i t was found that in soils whichhave been heated a t looo the action on hydrogen peroxide isgreatly reduced, and that a further reduction in the action is pro-duced by heating a t 250O.Treatment of the soils with mercuricchloride, phenol, and formaldehyde had no effect, except a slightdiminution in the case of mercuric chloride, which is very difficultcompletely t o remove. From these results the1 conclusion is drawnthat the catalytic properties of soils are not essentially due t oenzymes and microbes, but rather t'o colloids.An investigation of the effects of toluene and carbon disulphide 23applied to soils manured with cotton-seed meal and ammoniumsulphate, respectively, showed that nitrification was not appreciablyaffected by about 0.1 C.C. of toluene per 100 grams of soil; largeramounts were injurious, and even inhibited nitrification for a time.The largest amount employed was 1 C.C.per 100 grams, and fromthe effects of this the soil recovered in about five months.Carbon disulphide had no appreciable effect on the accumulationof nitrates except when more than 1-0 C.C. was added to 100 gramsof soil. A temporary retarding effect was then produced, which,however, did not last long, even with 5 C.C. per 100 grams of soil.Soils in which nitrification is inhibited for twenty weeks bylarge amounts of toluene or carbon disulphide may completelyrecover their nitrifying power without reinoculation.A study of the development of Protozoa24 in various media-ammonifying solutions containing bloodmeal, hornmeal and pep-tone, nitrifying solution, Giltay's denitrifying solution, etc., whichwere inoculated with soil, showed that, a close relation existsbetween the development of Protozoa and that of the bacteria,the maximum activity of both corresponding very closely.Thismay be due to the Protozoa taking an active part in decompositionstaking place; i t seems, however, more probable that the Protozoalive on the bacteria, and this view is supported by the fact thatthe protozoal activity lags slightly behind that of the bacteria.This was very marked in the case of the nitrifying solution, inwhich the encystment of the Ammbz was not complete until somedays after the ammonia had disappeared.Of the different Protozoa, the flagellates generally appeared first,and were almost immediately followed by the ciliates. These, afterH. Kappen, Bied. Zentr., 1914, 43, 145 ; A., i, 644.A.Cunningham and F. Lohnis, Centr. Bakt. Par,, 1914, ii, 39, 596.23 P. L. Gainey, Csntr. Bakt. Par., 1914, ii, 39, 584; A., i, 236AGRICULTURAL CHEMISTRY AND VEGETABLE PHYSIOLOGY. 223a prolonged period of activity, encyst, and are followed by theAmoebae, which seem to prefer a medium containing few or noactive Protozoa.Practically the same fauna was found in each of the solutionsemployed, and an associatioln of certain Protozoa with definitespecies of bacteria was, in the case of the Ameba, in the nitrify-ing solution.As regards the effect of heat on active and encysted Protozoa,it is shown that the active forms are killed a t 44--54O, flagellatesbeing the least, and ciliates the most, resistant, whilst the cysts arekilled a t 70--72O. I n the case of soils which cool more slowly thanliquid cultures, it is considered probable that a temperature of55-60°25 would probably be as effective as 65-70° on solutions.A mmom'fica tion, Nitrification, and Denitrification.I n order to ascertain the relative powers of various ammonifyingorganisms under different conditions, a series of experiments hasbeen made in which three different soils were manured with fourdifferent nitrogenous substances, and inoculated with pure culturesof ammonifying organisms.26 It was found that with the sameorganism the ammonifying power depends a good deal on thenature of both the soil and the manure, so that it cannot definitelybe decided which, of the fifteen organisms used, is the best.Onthe whole, B.tumescens seems to be the most efficient. The highestefficiency with a manure was shown by B. mycoides, whilst withpeptone Sarcina Zutea gave the highest results. With dried bloodand fish guano, B. mycoides showed o-n'ly a moderate ammonifyingpower.Taking ammonification as a criterion of availability, the resultsindicate that dried blood is inferior to fish guano and cottonseedmeal.Results of considerable interest have been obtained in an investi-gation on the nitrification of ammonium salts, the object of whichwas to ascertain what intermediate products are formed.27 Theexperiments were made in filters, which were inoculated fromactively nitrifying sewage filters. The compounds identified werehydroxylamine salts, which were estimated, and salts of hypo-nitrous and nitrous acids, and there was always some loss ofnitrogen. The results are in accordance with the view that theprocw consists of successive hydroxylation of hydrogen atoms, andsubsequent elimination of water. It is, however, not evident that25 E.J. Russell and H. R . Hutchinson, J. Agric. Sci., 1913, 5, 152.26 C. B. Lipman and P. S. Burgess, Univ. CaZ. Publ. Agric. Sci., 1914, 1, 141. '' E. M. Mumford, P., 1914, 30, 36224 ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.these initial changes were brought about by the nitrifyingorganisms, as a mixed culture was used. I n any case, the resultsare of great interest.That intermediate substances are produced by nitrifying organ-isms seems to be proved by a number of experiments which havebeen made on the rate of nitrification of ammonium salts andvarious organic compounds.28 The substances were sub jetted to theaction of a mixed culture of hydrolytic and nitrifying organismsobtained from the secondary contact' beds of a sewage works.A tshort intervals the amounts of nitrogen as ammonia, nitrites, andnitrates were estimated. It was found that carbamide, uric acid,asparagine, glycine, methylamine sulphate, acetamide, ammoniumoxalate, and sulphate all nitrify a t about the same rate, and thatthe maximum amount of nitrogen recovered as nitrate was 95 percent., owing, presumably, to losses by aeration and by the inter-action of ammonia and nitrous acid.The chief interest in these experiments is the temporary dis-appearance of nitrogen in the case of the ammonium salts.Afterfifty-seven days, only 57 per cent. of the total nitrogen of theammonium sulphate added was present in the three forms, and67 per cent. in the case of ammonium oxalate, indicating the pres-ence of some compound intermediate between ammonia and nitrousacid, containing about 40 per cent., more or less, of the totalnitrogen.Thiocarbamide and aniline sulphate failed to nitrify. Thelatter substance is probably decomposed into ammonia and phenol,the phenol being a t once destroyed by the bacteria; 90 per cent. ofthe nitrogen was recovered as ammonia.I n order to ascertain the influence of season and cultivation onthe activity of soil bacteria, samples of soil, taken a t intervals ofabout five weeks, were mixed with organic nitrogenous manures,and the rates of amnionification and nitrification determined.29As regards ammonification of such substances as meat, horn, andblood meals, there was a rise from August to October, then atendency to fall in November, and a rise to a maximum inDecember.A minimum was reached in Pebruary, and a lowmaximum in April, followed by a slight fall t o July, and probablyAugust. The nitrification results were similar, except that thespring maximum was in March, whilst the fall commenced in April.The variations in both ammonia and nitrates were slight, owingprobably to the unusually mild winter, and the December maxi-mum is attributed to the same cause.P. M. Beesley, T., 1914, 105, 1014.H.H. Green, Centr. Bakt. Par., 1914, ii, 41, 577; A., i, 1113AGRICULTURAL CHEMISTRY AND VEGETABLE PHYSIOLOGY. 225I n these experiments, the soil samples were taken both from aport'ion of the experimental field which had received autumn culti-vation arid from another portion which was not touched untilploughed in the spring. Although the crop results showed asuperiority of 30 per cent. as regards nitrogen in favour of autumncultivation, the bacteriological results failed to reveal anydifference.An investigation of the effects of irrigation and of crops on thenitrifying power of soils3* showed that irrigation water caused areduction in nitrification as indicated by laboratory experiments.The effects of crops varied both with the crop and the manure.Soil from lucerne land produced the greatest amount of nitratesfrom ammonium sulphate, whilst 61th dried blood, soil from theoat plots gave the highest results.The lowest nitrifying power,with both manures, was found to belong t o the fallow plots, indicat-ing that all the crops employed have a stimulating action onnitrification.Comparing the soil samples taken a t different depths, i t is shownthat about 90 per cent. of the nitrate found in the first 150 cm.of soil is produced in the top upper 45 cm.A further study of the effect of crops and cultivation onbacterial activity31 has been made with a considerable variety ofsoils, all of which, as frequently happens in the arid soils of Utah,contain plenty of mineral food and calcium carbonate, but notmuch nitrogen.It was found, in the first place, that cultivatedsoils contained about twice as many bacteria as the virgin soi1,thati t produced 30 per cent. more ammonia from dried blood, and twiceas much nitric nitrogen as the virgin soil. Comparing the influenceof the crops, i t is shown that the lucerne soil produced much lessiiitrat'e than the wheat soil. Fallow soil which was hoed containedfewer organisms than the others, but their activity was greater, andtheir production of ammonia and nitrates higher than any of theothers.The results of anzrobic experiments in which organic substances,such as peptone with meat extract, and peptone with dextrose,were inoculated with sewage filter huinus32 showed that half ormore of the gas evolved was hydrogen, the rest being a mixture ofnitrogen and carbon dioxide, varying in quantity according t o thenature of the organic matter.When nitrates are added, nohydrogen is evolved, and there is a greatly increased liberationof nitrogen; a small amount of carbon dioxide is evolved, and aconsiderable amount of methane. Evidence was obtained that theI. G . McBeth and N. R. Smith, Centr. Bakt. Par., 1914, ii, 40, 24.REP.-VOL. XI. Qy1 J. E. Greaves, ibid., 41, 444. 32 W. Hulme, T., 1914, 105, 623226 ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.production of nitrites is due to some enzyme secreted by theorganism, the enzyme being again reduced to its natural state bythe nascent hydrogen produced by the organism.The nitratesare then reduced to nitrogen by the action of hydrogen and carbondioxide.Experiments with twenty-eight well-known, spore-producingbacteria showed that twenty of them reduce nitrates in the presenceof dextrose, and seven others in the presence of peptone.% In somecases the nitrites produced seemed to have a toxic effect, whichprevented their accumulation ; in the presence of peptone, however,there was a considerable production of nitrites (up to 4 per cent.with B. tumescens and B. subtilis). Production of nitrites andammonia is found to depend on the composition of the nutritivesolution, and especially on its reaction, alkaline solutions, such asare obtained when peptone is used, being favourable to the pro-duction of nitrites, whilst with acid solutions, such as result fromthe employment of dextrose, ammonia is produced.Experiments with B.tumescens showed that the whole of thenitrogen of the reduced nitrate, which was not in the forms ofammonia and nitrites, was assimilated by the bacteria. The con-clusion drawn from these results is that the object of the reduc-tion of nitrates is to utilise the nitrogen, and not the oxygen.A number of ammonif ying experiments, in which copper, zinc,iron, and lead sulphates were added to a sandy soil in amountsvarying from 0.005 t o 0.25 per cent., showed only relatively slighttoxic effects; the action was generally more marked a t concentra-tions below 0.1 per cent. than at those above that amount. Nostimulation was observed a t any concentration.34Nitrification, on the other hand, was very considerably stimu-lated a t the higher concentrations up to 0.15 per cent., exceptin the case of lead sulphate.A t the lowest concentrations,0.0125 per cent., the metals were either slightly toxic o r withouteffect.Whilst the addition of 4-6 per cent. of calcium carbonate tosoil containing dried blood was found to increase ammonification,twice these amounts of calcium carbonate gave a smaller increasein the ammonia produced, and quite small amounts of magnesiumcarbonate (0.1 per cent.) retarded ammonification.35 The sameamount of magnesium carbonate completely inhibited nitrification ;denitrification, on the other hand, was only retarded by largeramounts of magnesium carbonate.It seems The results, if confirmed, are of considerable interest.~3 M.Klaeser, Ber. deut. bot. Gcs., 1914, 32, 58 ; A., i, 462.34 C. I:. Lipman and P. S. Burgess, Uniu. CaZ. Publ. Agric. Sci., 1914, 1, 127.y5 W. P. Iielley, Bied. Zmtr., 1914, 43, 149 ; A., i, 644AGRICULTURAL CHEMISTRY AND VEGETABLE PHYSIOLOGY. 227evident, however, that an unexpected complication is introducedinto vegetation experiments on the lime-magnesia ratio, especiallyas the addition of calcium carbonate seems to have no effect indiminishing the toxic action of magnesium carbonate on ammonify-ing and nitrifying organisms.I n order to throw further light on the origin of the accumula-tions of nitrates in certain soils in Colorado and the neighbouringSt'ates, t o which reference was made in previous Reports, theamounts of nitrates have been estimated in a number of shales,sandstones, and limestones of the old inland seas, as well as in alkdiand in ash material collected in its original state.36 The affectedarea, so far as is known, is within the section covered by the oldCretaceous and Tertiary seas, and it is found that large amountsof nitrates are present in the rocks of these formations, whilst theJurassic shales and sandstones contain much less.The maximumamount of sodium nitrate in Cretaceous shales was more than 1 percent., whilst alkali was found to contain as much as 3-35 per cent.The high local results are attributed to the low rainfall, andespecially to the protecting covering of clay.Taking the averageamount of sodium nitrate in fifty-eight samples as 0.104 per cent.,it is calculated that the amount present in the Book Cliffs areain Utah and Colorado would be a t least 90 million tons.The results, along with those previously obtained, seem clearlyLo indicate that the nitrates of the affected areas are derived fromthe accumulations of ancient deposits.On the other hand, evidence has been obtained, by means ofnitrification experiments with Colorado soils, that not only the soilsfrom areas in the incipient stage of steririty, but normal soils aswell, have a very much greater nitrifying power than foreign soils.37The nitrifying flora of the Colorado soils seems to be distinct fromthat usually found in other soils, either consisting of quite differentorganisms or else of different strains.Whilst other soils producethe largest average yields of nitrates from dried blood, next fromammonium cairbonate, and least from ammonium sulphate, withColorado soils the order is reversed. Chlorides inhibit nitrifica-tion, whilst large amounts of nitrates seem to be without effect.On the shength of these and previous results, showing the highstmmonifying power which these soils were found t o possess, andalso the presence of a l p , chiefly Nostocaceae, for nitrogen-fixingorganisms to feed on, the opinion that the high amounts of nitratesare derived from atmospheric nitrogen is maintained.Whilst the theory that the nitrates are mainly derived from the36 R. Stewart and W.Peterson, Utah. Agric. Coll. Exper. Stat, Bull., 1914, 134 ;37 W. G. Sackett, Agric. Exper. Stat. c'ol. A g r i c . 002. Bull., 1914, 193.A., 1915, i, 51.Q 228 ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.deposits of the old inland seas seenis the more probable for severalreasons, the Colorado nitrifying organisms seem to be quiteexceptionally active, and it would be interesting if they shouldprove to be related to Winogradsky’s vigorous Quito orga,nism.It has been suggested that the latter is descended from still moreactive microbes responsible for the Chile nitrate deposits.Movements of Nitrates in Soils.The observations made some time ago by Miintz and Gaudechonon the extreme slowness with which nitrates diffuse in arablesoil have been confirmed by several experiments.38 I n sandyand clayey loam containing 13-5 and 16.8 per cent.of water,only relatively small amounts of nitrates diffused to a distance of15 cm. in four months; a considerable diffusion in that time didnot extend beyond 10 cm. Under practical conditions, diffusionis therefore comparatively unimportant, nitrates being carrieddown into the subsoil by rain, and again brought t o tlie surfaceby capillarity. I n a dry season, nitrates which were depositeda t a depth of 25 cm. rose in eleven days t o within 8 cm. of thesurface, whilst nitrates deposited a t a greater depth rose more than40 cm. in a month.I n order to show the effect of the same amount of nitrates atdifferent depths on the growth of beet, five small plots werearranged, in which the nitrate (500 kilos.per hectare) was applieda t depths of 5, 10, 17, and 30 cm. respectively. The experimentsalso included an unmanured plot, and a similar series of plotswithout a crop. Estimations of nitrates in samples of the soilstaken a t different depths from April 15th to August 16th, and atdifferent depths down to 40 cm., showed that on the fallow plotsthe effect of rain was to distribute the nitrates in the zone betweeii10 and 30 cm., and to increase the nitrates between 30 and 40 cm.;there was no loss of nitrates. As regards the beet plots, it wasshown that the deep application of nitrates gave the best yield,owing to tlie better distribution of the nitrates. This is attributedto the upward movement brought about by the growing crop duringthe period of active vegetation, which seenis to result in a betterdistribution than that caused by rain.It is therefore consideredundesirable, as well as unnecessary, t o apply the manure in instal-ments. This would not apply to a winter crop in a wet climate,when the advantages of autumn manuring with nitrates may bemore than counterbalanced by losses.A study of the amounts of nitrates in arable soils, based on theresulta of numerous estimations of nitrates in cropped and un-Y8 L Malyaus and G. Lefort, Ann. Sci. Agrm., 1913, [iv], 2, ii, 705AGRICULTURAL CHEMlSTRY AND VEGETABLE PHYSIOLOGY. 229cropped soils a t different times of the year, showed that the amountsrarely exceeded 6 per million in sandy soil, 23 per million inloam, and 14 per million in clay soil.39 These maximum amountscorrespond, respectively, with about 30, 130, and 70 kilos.perhectare to a depth of 45 cm. The accumulation of nitrates wasgenerally found to take place most rapidly in the late spring orearly summer, after which the soils usually showed little, if any,gain in nitrates, and frequently a loss. I n the hot, dry autumnof 1911, however, the accuniulation went on in some cases untilSeptember.Comparing different kinds of soils, it was found that the amountsof nitrates varied more on loains than 011 clays and sands. I n claysoils, the winter losses were less; 011 the other hand, they accumu-lated siiialler amounts in June and July.Fallow soils were found to contain more nitrates than croppedsoils in the late summer and early autumn, allowing for theamounts taken up by the crop.The rapid rise in the amounts ofiiitratcs in the spring takes place, not immediately, but some timeafter the warm weather begins.An investigation, in some respects similar t o the one just referredto, has been made at Scania, in Sweden.*O Nitrates were estimateda t intervals of seven to ten days, to a depth of 30 cm., in the soilof a field on which different crops were grown successively from 1907to 1911; from 1909, fallow plots were included. In the croppedsoil, the amount of nitrogen as nitrates never exceeded 22 perniillion, whilstl in the bare soil the maximum was 33 per million.Comparing the amounts of nitrates in the plots under differentcrops, the maximum amounts of nitrogen were 14 per million inthe case of beet, 8 to 9 per million with wheat and peas, whilstuiider grass ths lowest results were obtained-1.5 per million.When, however, the grass was dug in, the nitric nitrogen rose t o6 per niillion, and by the middle of November to 31 per million.Application of dung resulted in vigorous nitrification, after whichthere was a fall in the amounts of nitrates, due partly to the wheat,crop and partly t o leaching by rain, so that by the spring theamount of nitrates in the soil was low.I n the early summer therewas again a rise, due to increased nitrification, and perhaps to aniovement of nitrates from the subsoil upwards, which, however,was not maintained, owing t o increased assimilation by the crop.The effect of vegetation and tillage was shown by an experimentin which a grass plot was divided into three parts, one of whichremained under grass, whilst the second was freed from vegetation,j Y E.J. Russell, J. Agric. Xci., 1914, 6, 18 ; A., i, 471.Jo RI. M'eibull, K. landtbr. Handl. Z'idskr., 1914, 53, 6 5 ; A., 1915, i, 61230 ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.and the third dug to a depth of 30 cm. On the three divisions, thenitrogen as nitrates averaged, respectively, 2.4, 6-5, and 11.3 permillion.I n order to ascertain whether i t is possible t o detect the pointa t which nitrogenous manures become necessary, nitrates wereestimated, during July and August, in eight unmanured plotsunder sugar-beet.The yields were estimated both on the un-manured and manured plots. Indications were obtained that wherethe nitrogen as nitrates fell to 2 per million by the end of July,applicatJons of nitrogenous manures resulted in a fairly largeincrease in the yield, whilst with a later fall in the nitrates the effectof nitrogenous manure is less marked. Similar results were obtainedwith other crops. I n an experiment with mangolds, where nitro-genous manure gave a large increase, the unmanured plot was foundto contain only 2 per million of nitric nitrogen as early as June.The " critical " period will vary with different crops.Toxins cund Stimulants.Reference has already been made to an organic substance foundin an acid soil which is toxic to one kind of plant and stimulatingto another; also t o a tonic condition produced by heating Boils,attributed to the formation of an organic toxin, but possibly dueto ammonia, which, it is known, may be produced in sufficientquantity.I n connexion with the question of the production by plants ofconditions inimical to succeeding plants, experiments with a varietyof plants grown in sand showed that the second crop was consider-ably reduced, and that the third crop was further reduceld.41 Thetoxic action was not confined to plants of the same kind, but wasmanifested in the case of other plants. Similar results wereobtained by adding to the sand roots grown in another pot.Onthe other hand, when the roots of the first crop were removedbefore sowing the second, the toxic effect was reduced somewhat,but, was stiil very marked.Better results were obtained by wash-ing the sand.It is considered possible that the injurious effects may, in part,be due to the production of alkalinity, and it is shown that, ofthe plants employed, those which produce the greatest alkalinity(millet and camelina) suffer the moat when the crop is repeated.I n accordance with the resulk of Whitney and Cameron, it wasfound that soil extracts frequently contained toxic substanceswhich were, however, equally toxic to different plants. When theD. Prianischnikov, Re'v. Ge'n. Sot., 1914, 25, 563 ; A . , i, 1208AGRICULTURAL CHEMISTRY AND VEGETABLE PHYSIOLOGY. 231extract of a black soil was distilled, and both distillate and residuewere employed for water-cultures, the growth obtained in the dis-tillate was similar to that obtained in a normal solution, whilst theresidue gave very slight growth.When the distillation wascarried out under diminished pressure, growth in the residue wasstill more restricted. The toxicity of the soil extract is entirelyremoved by filtration through charcoal.No toxic effect was observed when three successive crops ofetiolated oats were grown in the same solution.The injurious action of grass growing over the mots of fruittrees varies very considerably, according to the soil. On theshallow and not very rich soil of the Woburn Fruit Farm, whichis on the Oxford clay, the effect is often fatal, whilst a t LongAshton, where the soil is rich and deep, the injurious action ofgrass is only slight.I n the case of an old garden soil at Rarpen-den, no toxic action was observed.The results obtained a t Woburn42 seem to exclude the possibilityof the injuriop effects of grass being due to differences such asthe supply of water, alteration in the aeration of the soil, accumu-lation of carbon dioxide, alkalinity or acidity, etc., so that i t seemsprobable that the action might be explained by the production ofa toxin, either as a root secretion or, perhaps more probably, adecomposition product of the debris of the growing roots.Experiments were accordingly made in which grass was grownover the soil in which the trees were planted, so arranged thatwhilst the grass roots were not in contact with the soil containingthe tree, the leachings would reach the tree roots in a few minutes.Under these conditions, the same injurious effect was observed aswhen the trees and the grass shared the same soil.When, on theother hand, the grass is grown on trays away from the trees, andthe leachings from the grass are exposed to the air for an hour ortwo before being applied to the tree, their action is no longertoxic, but beneficial.The experiments were extended so as to include, instead of trees,a number of other plants, such as tobacco, tomatoes, and mustard,which received the drainage from clover; also Festuca, clover,mustard, and Dactylis, which received in each case leaching fromplants of the same kind grown in trays over the pots.A relductionoccurred in each case, varying according to the plant grown.The beneficial effect of oxidised leachings, already referred to, isalso obtained when the trays containing the grass are removed fromthe pots, provided this is not unduly delayed. If the plants havea Duke of Uedford and S. P. U. Picliering, Zoc. cit232 ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.been injured beyond recovery, and hard-wooded plants soon becomepermanently stunted, no beneficial effect is, of course, t o beexpected.The conclusions drawn from these experiments are that a sub-stance is produced from the roots of all crops, which is toxic t oother plants, and still more so to plants of the same kind, and thatwhen oxidised by air the toxin is converted into a stimulant.There is, however, no evidence that the stimulant is an oxidationproduct from the toxin rather than from some other constituentof the drainage.It does not seem very clear why the leachings from the trays areinjurious to the plants in the pots (presumably drainage from tlicpots would produce similar results if transferred t o the trays)whilst it is without action, as soil solution, before i t drains out ofits own pot.If it should be proved that the stiniulant is formed by theOxidation of the toxin, and not from some other substance, theni t follows that every growing crop results in the formation of astimulant.I n practice the stimulant might be expected t o havemore influence than the toxin, a t any rate on arable land, sincethe toxin would no doubt be oxidised during the interval betweenthe crops.For how long the stimulant resists oxidation remainst o be ascertained.A substance having considerable stimulative properties has beenobtained43 from peat which had been incubated with a mixedculture of aerobic organisms for two weeks. It was found, in thefirst place, that when seedlings of Primula malacoides were treatedtwice in six weeks with an aqueous extract of 0.18 gram of thepeat, the plants grew t o twice the size of other plants not sotreated. Stimulative effects were next obtained with wheat seed-lings by employing a solution of the residue of an alcoholic extractof the peat, and also the phosphotungstic acid precipitate from anaqueous extract of the same residue.A t the end of five weeks, theplants which had been treated with the substance extracted byalcohol showed an increase of 21.1 per cent. over the check plants,which received only the complete plant food, whilst the pots whichhad been treated with the phosphotungstic acid precipitate gave anincrease of 29.4 per cent. Experiments were then made t o comparethe effect of the phosphotungstic acid precipitate with that of thesilver fraction corresponding with Funk's vitamine. I n seven weeksthe pot with the phosphotungstic acid precipitate showed anincrease in dry produce of 22.7 per cent., and the silver fractionan increase of 17.7 per cent.W. B. Rottomley, Proc. Roy. Soc., 1914, [HI, 88, 237 ; An?&.Bot., 1914, 28,531 ; A., i, 1208AGRlCULTURAL CHEMISTRY AKD VEGETABLE PHYSIOLOGY. 233Wheat seedlings in water-cultures with pure food solution alonegained in weight in ten days, after which there was a logs, result-ing in a loss on original weight of 8.4 per cent. in fifty days.Addition of 0.35 per million of the silver fraction resulted in acontinuous increase, and a final gain of 54.9 per cent. in the sameperiod. Results similar t o these were obtained with wheat seed-lings from which the seeds had been removed.No stimulating substance could be obtained from the original,untreated peat.It is suggested that certain substances are formed duringgermination which enable the embryo to utilise the food supplied,and that, after the seedling becomes independent, some other sourcebecomes necessary.The peat stimulant seems t o be able t o takethe place of this substance in both stages of growth, and must,presumably, be formed during the usual huniification processes iiisoils.Whilst the stimulative effects of the substance from bacterisedpeat seem evident, the conclusion that tlie substance is not oiilya stimulant, but is essential, seems hardly justified, since it ispossible t o obtain fully-grown wheat plants in absence of anyorganic matter.I n vegetation experiments with toxic substance and stimulants,much depends on the methoids employed, and it is evident thatresults obtained with water-cultures and in soils cannot be ex-pected to agree closely. I n water-culturw the plants are subjectedt o the action of the whole of the substance added, if not precipi-tated, whiIst in soils the substance may not only be more or lessabsorbed, but may be expected to influence the bacteria as well asthe plants, so that, in addition to the direct toxic or stimulativeeffect, as the case may be, on the plant, an indirect action in thesame direction, or possibly reversed, due to aotion on the soilorganisms, is not a t all unlikely.The results of water-culture experiments with different sub-stances indicate that plants are better able to resist the actionof injurious substances in summer than in spring or winter.44The highest indifferent amounts of zinc sulphate vary, accordingto the season, between 0-2 and 0.04 mg.per litre in the case ofbarley, and between 0.2 and 0.05 mg. with peas. Arsenious acidand arsenites are found t o be more toxic, especially with peas,than arsenic acid and arsenates. Boric acid is less toxic than zincand arsenic, being injurious only when the amount exceeds 10 partsper million.No stimulating effect has been observed with zinc and arsenic a tW. E. Brenchley, Ann. Bot., 1914, 28, 283; A., i, 790234 ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.any concentration down to 0.005 mg. per litre in the case of zinc,and 0.02 mg. with arsenic acid. Boric acid, at the rate of 10 partst o 0.05 parts per million, has a stimulative effect on peas; in thecase of barley, the appearance of the plants seems to indicate stimu-lation, but this is not confirmed by the weights of the produce.I n pot experiments with wheat grown in s o i p i t is shown thatzino salts applied in quantitiw up to 0.1 per cent,.have a stimu-lating effect, especially on the production of straw, which showsvery considerable gains. Larger amounts are toxic. Of the differentsalts employed, the nitrate proves to be more active than thecarbonate or phosphate.Copper, as sulphate, applied at the rate of 0.01 t o 0.02 per cent.,has a stimulative action, whilst larger amounts are toxic andsmaller amounts without effect. With manganese phosphate andcarbonate, and cerium oxide and sulphate, the results arenegative.I n an unproductive, sandy loam, which did not respond well t ogeneral manures, t'he application of four different manganese saltsand the dioxide resulted in every case in an increased yield.46Stimulation varied, however, both with the.salt and with theamount added. The best results were obtained with 50 parts permillion of the chloride, which increased the yield by 31 per cent.The smallest gains were obtained with manganese carbonate anddioxide.On the whole, applications of 25 to 50 parts per million, corre-sponding with 14 to 28 kilos. per hectare, gave the best results.Very different results were obtained with a productive clay loam.I n t'his soil, manganese failed to show any appreciable increasewith any manganese salt; sometimes there was a slight depression.Further experiments on the growth of wheat in aqueous extractsof different soils showed that addition of manganese salts hadsimilar effects.In extracts of poor, unprolductive soils, manganesesalts increased growth and the oxidising power of the roots. I nextracts of productive soils, oxidation was again increased, whilstthe growth was diminished. The conclusion drawn from theseresults is that the beneficial action in unproductive soils is due toincreased oxidation resulting in the destruction of toxic substancesin the soil. I n productive soils, injury may result from excessiveoxidation.The results of a field experiment on an acid, clay loam showedthat all of the five crops grown were injured by manganese salts,45 J. A. Voelcker, J. Roy. Ayric. S'oc., 1913, 74, 411 ; A . , i, 1192.46 J. J. Skiliner and M.X. Sullivan, U.27. Dept. Agric. Bull., No. 42, 1914 jA., i, 1196AGRICULTURAL CHEMISTRY AND VEGETABLE PHYSIOLOGY. 235and that the oxidising power was reduced. Failure is, in this case,attributed t o acidity.Other experimenb with manganese salts have been made, someof which indicate that only small amounts can be applied withadvantage,47 whilst according to others the amounts required areso large that it is doubtful whether the use of manganese salts canbe remunerative.48 This divergence is no doubt due to the differentcharacters of the soils.Alkali salts have both toxic and stimulative actions, accordingto the concentration, on the germination and growth of rice.49The maximum stimulation was obtained with N / 500-solutions inthe case of magnesium sulphate, with N/lOOO-5000 in the caseof magnesium and alkali chlorides, whilst with sodium sulphate,chloride, and carbonate the maximum stimulation was withN/50-100-, N / 100-, and N / 100-500-solutions, respectively.Most of the salts were toxic in concentrations above N/100.When, however, two of the salts, even in iV/lO-solutions, are mixedin suitable proportions, the toxic action of each is more or lesscompletely overcome.This is mainly due to the antagonism ofthe cations, the antagonism of the anions being relatively feeble.It is also shown that bivalent cations are st,rongly antagonistic tounivalent cations, but that univalent cations do not very markedlyantagonise bivalent cations.Neither barium nor strontium can take the place of calcium incounteracting the toxic action of sodium and manganese salts;barium increases the injury, i f anything.I n mixtures of threesalts, all of which are toxic at the concentrations employed, growthis generally better than in two of them.Plant Nutrition and Maizures.Fixation of nitrogen by Azotobacter is found to be greater whenmixed cultures of different strains are employed than with purecultures of the same ba~teria.5~ The presence of humus, even inconsiderable amounts, seems t o have no unfavourable effect onnitrogen-fixation, and small amounts of sodium nitrate have verylittle effect. When, however, the amount of nitrogen as nitrateexceeds 2.5 per cent. of tKe carbon present), fixation of nitrogenis retarded, or checked altogether.As regards the effects ofdifferent forms of nitrogen, humus gives positive results, whilstwith humus from green manure negative resulte are obtained.47 0. M. Shedd, J. Ind. Eng. Chena., 1914, 6, 660; A., i, 1164.48 T. Pfeiffer and E. Blanck, Landw. Versuchs-Stat., 1913, 83, 257 ; A . , i, 243.49 K. Miyake, J. Coll. Agric. Tohoku Imp. Univ., 1914, 5, 211.50 J, Hanzawa, Centr. Bukt, Par., 1914, ii, 41, 573 ; A . , i, 1113236 ANNUAL REPORTS ON THE PROGRESS OF CHEMISTRY.These results seem t o show that in natural soils fixation ofnitrogen can only in very exceptional cases be retarded by thenitrogen compounds present. Nevertheless, the amount of nitrogenfixed in this manner, in ordinary arable soils, must be conipara-tively insignificant, and soils which contain high amounts oforganic carbon and nitrogen, from repeated applications of dung,soon lose much of their carbon and nitrogen when manuring isdiscontinued.This has been found t o occur even when the cropgrown is clover, which in a purely mineral medium, without com-bined nitrogen, leaves a considerable nitrogenous residue.The results of field experiments, in which oats were manuredwith sulphur, showed that no beneficial effect was obtained, theyields being, if anything, slightly depre~sed.5~ P o t experinleiits iuwhich mustard, rape, and clover received sulphur at the rate offrom 3.4 to 13.4 kilos. per hectare, gave negative results.52It has been observed in the case of wheat grown in the absenceof silica that plants which were attacked by rust sufferedseverely, the rust spreading very rapidly.53 It is accordingly sug-gested that cereals grown on dolerite and basalt soils should sufferless from attacks of this kind than when grown on granite soils,provided that the climate and the weather conditions are the same.The losses in nitrogen to which farmyard manure is subjecteldwhen stored may be due to the washing out of soluble substancesby rain, to volatilisation of ammonia, and to the fo'rm of denitrifica-tion, in which nitrogen is liberated, which might perhaps be betterterrned deazotisation, to distinguish it from denitrification withoutloss of nitrogen.It has been shown54 that, of the three processes, the first is muchthe most important t o be avoided. A manure heap exposed to rainfor three months not only lost 24 per cent. of its nitrogen, but morethan 20 per cent.of the dry matter as well. I n six months thelosses rose to more than 34 and 31 per cent. respectively, and therewas also a loss of 8 per cent. of the phosphoric acid.By keeping a heap under cover, the losses of dry matter aridnitrogen were reduced very considerably, and no phosphoric acidwas lost a t all. I n a heap which was sheltered from rain, but keptmoist by watering, the loss of nitrogen was doubled as comparedwith the unwatered heap; there was, however, no very appreciableincrease in the loss of dry matter.Apart from the washing out by rain, the relative importance ofthe losses by volatilisation of ammonia, and by the complete51 T. Pfeiffer and E. Blanck, Landto. Vcrsuchs-Stat., 1914, 83, 358 ; A., i, 469.52 J. A. Voelcker, J, Roy. Agric. SOC., 1913, 74, 419 ; A . , i: 1196.53 14. Lundie, South African J. Sei., 9 ; Chem. AJews, 1914, 110, 200 ; A., i, 1192,5J E. J. Russell and E. H. Richards, J. Bcl. Agric., 1914, 21, 800AGRICULTURAL CHEMISTRY AND VEGETABLE PHYSIOLOGY. 237reduction of nitrates, must depend a good deal on the weatherconditions. With a succession of showers, with intervals of dryweather long enough to give the maximum production of nitratesa t the surface, losses by denitrification would be very consider-able. That, no doubt, is what happened in the watered heapreferred to, but, on the whole, it is considered more likely thatthe greater loss will usually be in the form of ammonia.A new potassium manure has been prepared from leptite orcurite, a common rock in Central Sweden.55 The mineral, whichcontains up t o 11 per cent. of potash, is heateld with coal and ironfilings in an electric oven, with carbon electrodes, a t about 1SOOO.I n this manner a slag is obtained, which consists chiefly ofpotassium and aluminium silicates, 90 per cent. of the potassiumbeing soluble in hot 20 per cent. hydrochloric acid. As comparedwith potassium suIphate8, the results of pot experiments, in whichthe same amounts of potassium were supplied in the two forms,showed that the “electro-potash,” as the new manure is called,yielded 78 per cent. of the crop obtained with potassium sulphate.From experiments made in the United States, it has been esti-mated that a million tons of potassium chloride per annum couldbe obtained from seaweed.66Methods.Of the papers dealing wkh methods of importance in agriculturallaboratories may be mentioned those on the estimation of carbo-hydrates in plant materials,s7 a colorimetric method for nitritesand nitrate~,5~ methods for estimating acidity and carbonates iiisoils,59 and a modification of Konig, Hasenbaumer and Hassler’siiiethod for estimating the surface of soils.GON. H. J. MILLER.55 H. G. Soderbaum, Kungl. Lmdtbr.-Aknd. Hcindl. Tidskr., 1914, 53, 15.5G “ Production et Coii&oniniation des Engiais Cbiniirlues dms le Polonde.” Rome,5 7 W. A. Davis and A. J. I)niuh, J. Agric. Sci., 1914, 6, 153 ; A , , ii, 58858 E. A. 1,ctts and Miss F. W. Itea, T., 1914, 105, 1157.59 H. 13. Hutchinson and I<. McLennnn, C’he?iz. News, 1914, 110, 61 ; A,, ii, 7841914.A. .T. Daish, ibid., 255.J. Ayric. Sci., 1914, 6, 323.J. A. Hanlcy, J. Ayric. &i., 1914, 6, 58 ; A . , ii, 312