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CHEVALIER Bulletin on Tobaooo No. A-r> Publi.hed by direction of the Hon. SYDNEY A. FISHER, Minister of Aoriculture, Ottawa, Ont. Jaitiiary, lOOO 1943—1 I Ottawa, January 6, 1909. To the Honourable The Minister of Agriculture. Sir, — I have the honour to iuibmit hrrewith Bulletin No. A-.'i, of the Tobapoo Divinion entitled 'The Importance of Rotations in Tobacco Culture,' and prepared by If. O. riievalier, a8!ii8tanf agricultural expert in the Tobacco Division. In this bulletin M. Chevalier demonstratca the absolute necessity for a rotation in order to obtain good yields, and he warns planters to be on their guard against the waBting of their farm manures or the wrong use of indiistJrial fertilizers. They will also find therein the explanation of certain phenomena which perhaps they have not b'tliTto understood. I recommend that it should be printed for distribution. I have the honour to be. Sir, Your obedient servant, F. CHARLAN. Chief of the Tohdcco DivUion. THE IMPORTANCE OF ROTATIONS IN TOBACCO CULTURE. When wo coiisiik'r tlnj present pooi.ion of tobacco culture in Cunada, one fact inimeilintely »trikes us. How is it that in Hpite of the jiidicioui" selection of varieties and iif careful attention to details of cultivation, planters are unable to exceed cer- lain yields ttnally below those which they are entitled to expect. It appears to me that it will be interesting and useful to look into the reasons for this state of things, and, '1 possible, to ascertain the practical remedies. In the first place, notwithstanding the improvements lately effected in tobacco culture, we find that the yielda are diminishing every year. This is easily explained l)y the fact that the majority of plantei^ grow tobacco regularly every year on the same land. It is this successive cultivation of the same plant on the same soil tiiat in one of the reasons for the constantly decreasing yield. We are aware that tobacco, owing to its short season of growth, U one of those pluntVi that require the greatest amount of fertilizing elements. Indeed a tobacco plant in full growth removes daily from the soil: — Nitrogen 0-287 Potash 0-2S9 Phosphoric acid 0'601 Carbon 2:51.T Considering also how slow planters have been to make use of manures, whether farm yard or chemical, and that the waate products of tobacco, stalks and stemmed tibres,were fnquently thrown away, we see that with a plant which consumes every- thing and when practically nothing is returned to the soil, tht land will speedily become impoverished. Hardly more than two kinds of soil were chosen for tobacco culture: Virgin soil and alluvial soil, both exceedingly rich in humus. A tobacco plantation will never succeed without humus. The absence of a rotation and the failure to restore ingredients removed, are the principal causes of diminished yields. It will not be amiss perhaps if we dwell for a few moments upon the important role which humus plays in vegetation. This role is in agriculture a leading one. We can discuss it from two points of view: (1) as a means of disaggregation, and (2) as an agent of mechanical change. These two special properties are due to the considerable quantities which it contains of nitrogen and carbonic acid. Moreover, these two processes go on simultaneously. Two alternatives may present th?m- selvee: (1) Where tixv soil is rendered sterile from the lack of humus, and the consequent absence of nitrogen and carbonic acid. (3) Where a small quantity of nuniua produces disaggregation but causes no mechanical improvement ; so that 5 1943—2 rnutritive plcmoti.t «Mcapr> tho actiun of thr rfKits b.vnu»«' thiwo hdIuKU' inntoriftl« will bi' tartly ilriiiiird awiiy \ wati r-< of filtrntinn ami partly arrpntivl by «h:y wliirh n* we know imvmsw, rori^iilprab'n powrrn of flbicftiise it is so to sjH'Hk, the reflietim theie.)t". Never with fudi a manure can we hope to correct the drfoets of the soil. Annin. farmyard nuiiiwre. whatever its state of dtvonipositioii, takes n eonsider- nlilo time before it enn l>e trniwformed into humus. And then a lienvy apiilieatiun of farmyard manure, pure and simple, may have wriouri disadvantaKcs. In purtleular it may brinn alwut reversion, that is to say, tnuisition from a soluble to an insoluble condition of the sulphate of ammonia, for instance, which is much used in tobacco culture. The resulting humus forms with the sulphate tif ammonia a huniate of animi nia which by chemical reaction and also by niierol.i.' notion nuiy cause reversion, probably by dehydratntion, and end in the formation of lui insoluble composite amide from which consequently the plant will 1)0 unable to derive for, ', We must remember also that a soil too rich in humus will, owiufr to its cxces- .sivc acidity, delay considerably the process of nitrifieation, and may even arrest it altogether. And if virgin -oils very rich in humus have at first given good yields it was doubtless be<.ause the dkalinc element had neutralized the injurious excess of acidity. Certain growers, these of Lake St. Jean, for instance, who had omitted to burn the st.unps after the felling of their tre«^,only obtainetl poor harvests because of the acidity of the humus, which acidit; the carbonate of potash resulting from the burning of the vegetable matters could have neutralized. The application of lime, the use of which seems thus indicated, would, however, only partially solv.- the problem, for in addition to the difficultiw, met with in pro- cuririK lime and the riskf. incident to its excessive use it takes a long time to make Its influence felt. In fact the nitrification of humus differs greatly from that of minerals incorporated directly with the soil. Salts of ammonia, for instance, as well as those which originate during tlie development of ammonia generally, nitrify very quickly, those being nitrogenous substances directly nitrifiable. But it is not so with humus, the nitrification ef which is very slow, and there are even cases whfTP tlin nitriHi'iifion ili*'* not taki* plitcc at b11. It hetriru only whorn <)(><iii- tioii hnn <'oii«iclr that thf aiiimoniacnl liiiinatf in that wliirh coiitaini* the liirgi-ct proportion of iiitYi"' nilr.jiron, whilst piita'tsic and Koiiic hiiiiiato'4 will U- niui'h Ims rich. Tin- iiitroifniMiis (>|<-iiipnt in the latliT roines rritirt'ly froni iho trniiMfoniird huiiiiis. We cannot expect therefore to correct the want of humus quickly by heavy uppii- pations of furmynnl nuuiurc And btMidf- s.iU naturully fcrtilo arc alwnys much ^upt'rior to others. In tlw tirxt placi- tlwy obviate expensive opcMlions m-ciM!.ituteil by the inuinteuanco of the proiluotivciU's* of the R.ijl. AN" thii mitur.d fertility \.- chiiractrrizi'd by uliundiint fcod reserve- which kIvc to plntit« slowly, economically and with precision, the nutritive principles they need. In tliia remnrkublo way • iiature truly shows it* genius ' and justities the terms 'fat land" o.- ' Ian i of pri- tiiic vigour,' that is applied to soils of nafurnl fi rtilit.v wliicli it is so iuiportniit to prer-erve. ":t i» incontcstwhle that planters, although it was n long time ngo, found themselvf* in po-sp»sion of soils of this kind. Yet this natural fert lity tends ineviUibl/ to diHap|«>ar or at least to decrease rapidly. IJemoval of the crops, feed- i ig of farm animals, losses of nitrogen at the stable and in the yard by amnioniacal fiTinentotion, all result in rapid exhaustion of soil reserves. Wo no longer believe in the possibility of supplying the want of mineral sub- stances by strong applications of ehcmic.il manures; in fact tlics ■ by their nature are very (wluble and cons*'(piently ore apt* largely to disaptiear. isp(cIolly ii tobacco culture which requires a light deep .soil that lends itself ens ly to lossc by drain- aifo. The di«8(dving action of water is not the ^ame on all tli ■ mineral cMUstituonts of the soil. Potash and phosphoric n<'id, for instance, do not di-appear rcidily. Sul- phuric acid and nitric acid are easily lorit. ridorine also draiiu nway eisily, and this in tobacco culture is an advantage, because chlorine has nn nnfavournble effect upon the combustibility of tobacco. Of all the constituent elements of the soil, it is the lime which disappears with feTcatest facility. On this point there is nn imixirtant remark to be made. Tobacco needs a great deal of potash, and in soils po«r in lime potn-sic salts an' with difficulty changed into carbonat(>s when they are very soluble; tliiir tenilency to drain away is thus considerably reilneeil. For tobucco it is neces- sary therefore to choose a soil thot is not too rich in lime, nnd especially because when the snows are melting the excessive washing of the soil renders the drnining nway of the potash particularly easv. Once they have disnppeari-d many yeors will be required for the restoration of these valuable luitritlve reserves. Doubtles* •hesj. substances are not loPt since they accumulate nnd will become operative some day; hut this is not the object aimetl at by the use of chemical fertilizers, the action of which is expected to be rapid. 1 lie bick of humus nnd of mineral substances indispensable for plant growth, through a main cause of soil exhnnsticn, is not the only one. In fact in certain cases phenomena of a purely ehemieol nature may result in the insolubility of a fertilizing ingredient of the first importance, or may produce a substance injurious to the quality of the tobacco. In ground that is rich in lime and in I >- If I i 8 fprric salts humates and alkaline silicates are particularly liable to such a transfor- nintion. Thus silicate of potash, for instance, by the action of any calcareous salt, aiii..n>f.-,t other ohloride, may !« precipitated under the forni of nn insoluble silicate «.f lime by cnusiug the formation of chloride of potash. Here we find ourselves ociiifroiited with the type of reversion by precipitation. Salt- of iron would pro- iniiliir reaction, the silicate.-^ of sodn and potash alone beiiiR soluble. Aa we have seen tills pr.'eipitntion induces tlie formntion of chloride of potassium, a salt that is injurious to tobacco, because of the nature of its acid which acts very un- favourably upon combustibility. This last euasideriilion furnishes us with another reason whv for tobix-e . we should seek ii soil thut does not contain too large a pro- I)ortion of lime and stilts of iron. Now certain soils of Cnnailii arc rich in lime and in ferric o.\ide; this last salt, in particular. show.s its presence by the special colour it imparts to the soil which one meets with everywhere. The almast total ineornbiisfiliility of the toba<-co of St. Damase (Rouville Co.) is probably due to the exc.s.s of lime to which we refer, for the siils of that country exhibit a sufficient richness in potash from which we infer that potash is there present in the form of ehloriile. Anotiur important retrogression relates to the phosphates and determines the fixation of a notable quantity of phosphoric acid. The mono-calcic phosphate re- a<-liiipr on e of the surierphosphates in tiie soils where salts of iron and of aluniina and lime arc in excess. An eNce...s of lime any tlu' salts of iron and of lime. We should t]ier,.fore bo fortunate if we eonl.l make use of a soil rich in phos- phoric acid, which allows of the formation of humo-phosphates and does not let the humates /emain snseeplible of becoming insoluble. Further it is not a matter of indifference as to whether we obtain one or other of these last. The humates which relate to agriculture are very soluble, whilst humo-phosphates being much less so will present greater resistance to the draining away of the water. The dissolvants are the solution of alkaline carbonates. In conclusion we see that soluble phosphoric acid may be absorbed by humic matter or may be procipitate.1 by alkaline humates, this precipitation being accom- panied by the formation of humo-phosphates. These then are the various considerations which should be of assistance to ua in explaining the exhaustion of the soil and the inability of planters to increase their yields of tobacco at will. rnfortunately we are obliged to follow general considerations arising from the great kno-wn laws. Is there really a lack of humus in our tobacco soils? An there defective conditions of nitrification? Is there a lack of nutritive mineral elements! Is there ,n a word a due combination of the constituent mineral principles? We have here a sufficiently difficult problem to solve, and we tnmt that soon a laboratory attached tb the tobacco division will enable us to arrive at definite conclusions. Besides the chemical theories that we have just received, we should also take into consideration reasons connected with the climate and agricultural conditions grnerally. With regard to the climate it; is clear that Canadp, owing to the length of its winter, and the almost complete absence of any between season, is not par- ticularly favoured. Autumn cultivation 13 sometimes difficult, and one is often obliged to wait long before ent»?rinj- upon the spring cultivation, for the melting of the snow and the rainy season which follows, render the fields unworkable. But up to a certain point the activity and real of the planters as well as the beautiful sum- nior compensate for the unfavourable climatic conditions, and theref -e wo are not really faced with any very serious difficulty. From the agricultural point of view, arable cultivation and especially ploughing is of the first importance. Thus if the arable ^ed is not thick enough it causes sterility of the soil. In fact it is the deep soil that best secures the great reserve of humidity which is essential to tobacco. This humidity, so preserve.!, rises by capillarity to the surface. Thin layers on the contrary soon dry and are subjoctied to quick alterations of temperature. For soils that are not deep the carting of earth to increase the thickness of the arable bes of water is also n cause of sterility. In this ciise ludee re-establish a due proportion of nutritive constituents whilst obtaining from t!ie ^nil meanwhile all that it ciin give. Possibly the study of a rational system o{ rot.i- licii will furnish the solution of the problem. The rotation we recommend is a triennial one as follows:— (1) Tobacco. (2) A cereal. (-•{) Clover. if I! 1^3 it 10 We require an appropriate and economical rotation that ihnll enable u« to draw the greatest possible profit from the Hoil, whilst at the same time the formation of humue id being produced by considerable but not too heivy appli- cations of farm yard manure: First, in order to avoid the disadvantages enumer- ated above, and next because we have not at our disposal any very great quantity of manure. ' We apply the manure after breaking up the clover and wi plough boforc; the winter. We apply chemical manure in the spring at the time of th,, last ploughing, before the planting of the tobacco. An autumn ploughing follows the gathering of the t«bacco, and the cereal and tl. clover will be .mvn to?;th(T iu the spring. Tobacco being a plant that requires hoeing, is placed first in the rotation. By this means we get rid of j.o.^ious weeds which spring up from seods containci in the ^unu^^ and we can with no risk of infesting our soil „pply „t IcM^t 15 to 20 tons of farmyard manure to the acre. Itr is essential to perform this operation before winter and to plough in the manure as deeply as possible. In thij way frost wMl dor.ioy a large proportion of injurious seeds and ime-.n; th,, other seels will ger- minate rapidly enough, once the fine days of spring set in, and it will be easy by one or more light i loughings, to destroy these weeds, tiius twrfectly cleaning the lan.l besides increasing by so nuu-h our stock of fermenting organic substances, and return- ing completely to the soil all the nutritive elements which have served to build up the noxious plants. By the applicntnon of dirng upon the breaking up of the clover, we allow of the fermentation of the humus whilst supplementing the immediate requirements of nitrogen, smce as a matter of fact the nodules of this leguminous plant rapidly .yield assimilable nitrogen, and the soil will thus be able t» await the time necessary for the dung to decompose sufficiently to allow of its nitrification. There still remains the question of the choice of the cereal. And first, why do we choose a cereal nt all? Because owing to its fasciculated root system, the cereal only exhausts the .M.rfaoe of the soil and therefore conveniently succewls a plant like tobacco whose powerful roots deeply penetrate the ground. We have the choice between wheat, oats, rye and barley. Although coming well enough after tobacco, we can at once dispense with wheat, for after heavy nitrogenous manuring we should risk failure. Wheat too requires a great .leal of phosphoric acid, especially when earing, and moreover it succeeds best in free soils of due consistency, such as sandy loams or chalky clays, not too wet. In other words the soil suitable for wheat would l)o tcK) compact for tobacco, which needs a light and snn.ly s,.il. Ryo would suit better, for it is really the cereal for sandy soils, and .after tobacco would find its place in the rotation, since above all it needs n sandy soil well worked and autuiiui ploughed. The success of the rye crop depends essentially upon the thoroughness with which the soil has been worked. An ancient proverb thus expresses the agricultural law: 'Sow thy rye in powdered soil.' It will not be altogetlier out of place to state hrro exactly what is meant by light cobacco sandy soil. Fine sand alone is of no use. From the physical point of view, coarse sand is exceedingly i)ermeable, whilst fine snnd is a settling element, although its containing power may, so to speak, bo nil. In sandy soils which necessarily con- tain an iasufficient quantity of coagulntive elements, the formation of agglomerates 11 is extremely difficult. If fine aoil i« the dominating element the penetration of water is diflScult and the soil may be considered as essentially resistant, since the perme- ability of a soil depends upon tlie quantity of coarse sand that it containa. But wo know that the greater the fineni^s of the soil the less active are the disintegrating agento; consequentiy fine sand from the point of view of the constitution of the reserves of nutritive elements, is preferable to coaree sand. It follows that a soil suited to tobacco culture must contain in due proportions a mixture of fi-e and coarse eand; the fine sand is useful for the maintenance of reserves, the coarse as a means of permeability. It is the admixture of these two almost contradictory chnr- aitcri-itios which ounatitutea a good tobacco soil. Oats are less exacring than any of the certals, and practically they succeed everywhere. By this crop one can increneo the depth of ploughing for it likes a deeply-stirred soil. This would not suit wheat which requina a tirmer soil in order to avoid exiwsing the roots. Lastly, oats better than any other cereal, stands an insufficient pn-paration of the soil which is a valuable proptTty in Canada whire climatic conditions are not always favouralile to farm work. There remains barl.y. Barley is like tobacco, a plant of rapid growth; it re- quires therefore a rich and weU worked soil. Of all ccreala it requires the greatest stirring of the soil, and if it were not also so exacting it would do admirably for a crop succeeding tobacco in the rotation, because a hoed plant on account of the numerous workings that the soil receives leaves the land clear and well stirred. Aniuiiijot tiK-s,. four cc.cild we arc inclined to prefer oul.s, believing that this cereal best fullils the purpose we desire it to aeeoniplisli. Owing to their small requirements, oats will give a yield without manure and will utilize the phosjJioric acid proclneed, i.hosphoric acid being doubtless of little m(^ to the tobacco, but being indispensable to growth as wo have already seen. iJye is not nineh grown in Canada, espe.-ialiy in tin- province of Quebec, and it is hardly grown in Ontario, except for the distillery. As to barley, it is too ex bausting. We sow clover with the oats in the spring. We recommend a mixture of red with white clover. This last is common enoumdi and sueeccls in almost any soil, li is u!.so stroLgiy r.fiMuiit lo drouth uiul grows Well in eilicious soils, in fact it is in lhe.se -soils that it gives the finest yields. Red clover requirese a soil rich in clay; yet it will succeed in tobacco soils, since the last named plant also requires u sul.soil which ensures the necessary mois- ture. Lastly, red clover being finer than white, will improve the q\iality of the toilder. If one Is careful not to abandon the clover to pasture after tho harvest. It will have every elianee of giving a good crop. I have several times noticed liiat in many places farmers put their cattle into the young clover. One sees the defects of this practice from the trampling of th-^ animals. Nevertheless and in the special case we are now considering pa-sturage owing to the excrements of the animals could be pra.'ticed and would be a fairly good operation. We may choo.s.. between the two practices according as to whether our object be to enrich the soil with humus or to obtain a good crop of fiidder. The latter plan s«>ems to me to be preferred, it being nnderstoo.l that tb.> farm hsus enough meadows to supply the fo<«l re<|uireinents of the wtoek. 11 i I -t I'- il. u It ia scarcely nece.sary to justify the inclusion of a leguminous crop in the rotation which we recommend. The strong radicular ayHem of clover, penetrate, the soil deeply, but the chief part it plays is the enrichment of the soil through the fixation of nitrogen by its roots. We would draw attention to the breaking «p of the clover which ia a delicate operation, for the roots of the leguminous tend to raise the earth and to iroduoe what ,. calle,! a hollow soil. This disadvantage nui.t te avoided by str. .g ud repeated spring rolling. A large part of the manure buried with the first ,rop of the rotation will now be transformed into humus, and if we take account of the quantity of nitrogen fixed bv he root nodules, we perceive that at the completion of the rotation the returning tobacco w.ll begin to find ready for it an abundance of nitrogenous material. Finally, from the tobacco point of view alone, an alternate system of culture is preferable, for this method contributes powerfully to the destruction of insects in- jurious to tobacco and especially of cut worms and flies, in fact for many insects no other means of destruction are available. Ottawa, January. 1909. ;i I