Where are the New Discoveries in Soil Science Leading?I. The Physical Chemistry of Soil-Plant Relationships1

RICHARD BRADFiELD2

PHYSICAL chemists', as a rule, try to shy away fromsystems as complex as soils. In the early days,

many of them tried to find out about soils by study-ing simple systems which they thought had prop-erties something like soils — substances like charcoal,charred sugar, colloidal silica, iron, aluminum, kaolin,etc. In many cases such studies brought interestingfacts to light. I have always felt, however, that thebest way to find out about soils is to study soils, andthis report will be confined almost entirely to directstudies on soils or materials isolated from soils.

One has to start somewhere in a review of thissort, and I have chosen to start with the developmentof methods for isolating the colloidal fraction of soilsin large quantities. This was done for the first timein this country only a little over a quarter of a cen-tury ago. This step marked a distinct step forward inthe development of the physical chemistry of the soil.It was a first step towards producing from the soil amaterial which was very active from the physico-chemical standpoint and which was more homo-geneous, at'least from the physical standpoint, thanthe soil as a whole. It had this additional advantage:This material could be put in a test tube or beakerand measurements with which the physical chemistwas already familiar could be made on it with theequipment which the physical chemist already hadat hand. Here was a material which he could placein a bottle, handle with a pipette, run through aviscosimeter, flocculate in a test tube, and perform awhole host of similar operations which had beendeveloped in the study of the colloidal properties ofother systems.

This material had a number of very interestingproperties. When in the form of paste, it looked like,and felt like, axle grease. When it was dry, it hadthe binding power of Portland cement. When in di-lute suspension in water and stirred, it showedstreamlines, indicating that the individual particleswere not spherical. It was clear by transmitted lightand turbid by reflected light. When the sol was placedin an electric field, the clay particles moved towardthe anode, indicating that they had a negative charge.With most such materials it was impossible to reversethe charge by merely changing the hydrogen-ion con-centration. These sols were easily flocculated by elec-trolytes, and the usual valence laws for coagulationof colloidal materials by electrolytes were 'found tohold. It was found to have cation exchange proper-ties, behaving much like the synthetic zeolites in thisrespect, but it differed widely from zeolites in itsphysical properties and in the total amount of ex-changeable ions per unit of mass of material. It was

soon found that the physical behavior of these solsvaried widely, depending upon the nature of thecation with which they were saturated. This indicatedthe necessity of simplifying the system still more, iflogical systematic studies of the physico-chemicalproperties were to be made.

Fortunately, about that time colloid chemists de-veloped a new tool for the purification of colloidalmaterials — electrodialysis. In the process of elec-trodialysis, the colloidal material extracted from thesoil was treated with no chemical other than distilledwater. It was merely subjected to an electric fieldwhich seemed, at least, merely to accelerate the hy-drolysis of the exchangeable cations combined withthe clay and resulted in the formation eventually of ahydrogen-saturated clay relatively free from all ex-traneous electrolytes.

The process of electrodialysis itself revealed manyinteresting properties of the clay. Under suitableconditions it deposited on the anode membrane inthe form of finger-like projections which, in certaincases, completely bridged across the anode chamber.Occasionally one could even observe small bubblesof gas at the end of these finger-like projections, in-dicating that they were serving in a way as an exten-sion of the anode itself. The electrical conductivityof the clay when thus oriented was much higherthan when the particles were uniformly distributedthroughout the anode, compartment, indicating thatthere was a marked surface conductivity in such anoriented clay system.

One of the most useful purposes served by theelectrodialyzed clays was. their use in studying soilacidity. It had long been known that the acidity insoils was concentrated largely in the colloidal frac-tion, and when this isolated colloidal material wasfreed from all exchangeable bases and of all anionsin true solution by electrodialysis, we had, for thefirst time, real soil acids of a fairly high degree ofpurity, which could be used for many types of inves-tigation. Numerous titration curves were made, andit was found that this material behaved very similarlyto ordinary complex colloidal acids.

Studies of the relationship between the concentra-tion of the clay and its pH value gave the normaltype of relationship expected. Studies of the dis-tribution of the hydrogen ion of the clay acid withthe salts of other acids gave the type of distributionthat had been observed with other acids by physicalchemists a quarter of a century earlier. All theseobservations tended to clear up many of the per-plexing questions which had arisen through the yearsregarding the nature of soil acidity. There did not

'Contribution from Department of Agronomy, Cornell University, Ithaca, N. Y.2Head of the Department.

SOIL SCIENCE SOCIETY PROCEEDINGS 1946

seem to be anything mysterious or different aboutthese soil acids. They were merely colloidal acids oracidoids with a strength much higher than any of thesilicic acids which had been studied until that time.

Many were not satisfied to work with the colloidalfraction purified by electrodialysis and attemptedfurther fractionation by treating the colloidal materi-al with various types of solvents, the most commontreatment being the successive use of various acidsand alkalis, supplemented in certain cases by the useof a reducing agent which facilitated the removal ofcertain constituents, especially some' of the ironoxides. In this way, a residue was obtained whichseemed to be quite a bit purer than the originalmaterial.

Since analyses had revealed that this colloidalmaterial contained considerable organic matter inmany cases, an effort was made to obtain a purerproduct by removing this organic matter either byoxidation with a mild oxidizing agent like hydrogenperoxide or by dissolving it in a weak alkali. Manypeople at that time had the idea that the colloidalmaterial was a mere mechanical mixture of colloidalorganic matter and the inorganic complex. Theseattempts at purification by removing the organicmatter by either of the techniques mentioned revealedquite clearly that the natural colloidal complex inthe soil was not a mere .physical mixture, but thatthere was a closer bond between at least some of theorganic matter and the clay. We have much moreevidence of this now, and we commonly speak of theclay-humus complex.

It has been mentioned that it was observed quiteearly that the isolated colloidal material, when rapidlyshaken, showed streamlines, indicating that the par-ticles were not spherical. Systematic studies of theoptical properties of the clay sols confirmed this pre-liminary observation and indicated quite strongly thata high proportion of the particles in most .of the clayswas made up of plate-shaped crystals. As soon asX-ray diffraction methods for determining crystalstructure were sufficiently perfected, they were ap-plied to some of these colloidal clays and the crystal-line nature of the material was established beyondquestion.

This fact stimulated a great number of studies,which had as their objective the clarification of theexact crystal structure of the clay minerals. Whilethere is some disagreement on some rather importantpoints, there is common agreement on the existenceof four or five different types of clay minerals in themore important soils of the United States. All theseclay minerals have certain properties in common, butthey differ from each other in certain vital respects.

For a decade of so before the isolation of the col-loidal material in soils, soil scientists, devoted a greatdeal of attention to a study of the soil solution whichwas isolated from the soil by various techniques andwhich presumably represented fairly accurately theliquid phase which surrounded the soil particles andfrom which the growing plant secured the mineralnutrients essential for their growth. While such soil

solution studies were very interesting and revealedmany new facts about the liquid medium surroundingsoil particles, there was considerable question in theminds of many as to whether or not it representedaccurately the medium from which the roots of plantssecured their nutritive elements. There was a ques-tion as to whether there was .not a closer junctionbetween the root and the solid particle itself. Theavailability , of homoionic clay systems facilitatedstudies of this problem. It was now easy to mixclays saturated with different cations in any propor-tions desired and to study the up-take of these variousions by the plant. It was also possible to study theup-take of ions in suspensions containing clay par-ticles and similar solutions free from such clay par-ticles. Such studies indicated quite clearly that thesolid phase does exert an influence upon the up-takeof ions, and we find many references in the literaturenow to "solid-phase feeding".

The studies of hydrogen-ion concentration of hy-drogen clays, referred to above, revealed that in thecase of carefully purified clays-the hydrogen ion con-centration, as calculated from the potentials of anyof the electrodes used for measuring hydrogen-ionconcentration, was very much greater in the presenceof the clay particles than it was in the intermicellarliquid removed from the clay sol by ultrafiltration orsimilar techniques. This evidence pointed quite clear-ly in the same direction as the solid phase feedingexperiments listed above, and indicated that there isan ionic atmosphere surrounding each clay particlewhich is quite different from that in the free liquidbetween particles. Since various cations are moredifficult to replace from clays than others, it wouldbe natural to assume that the concentration of dif-ferent cations in this ion sphere surrounding theparticles might vary.widely. Several attempts havebeen made to determine the "activity" of these ions.The use of the membrane electrodes utilizing either

-membranes made of silicate minerals or suitably pre-pared colloidion-membranes seems to have consider-able promise for such studies.

If techniques of this type can be perfected, theyshould be of considerable value in interpreting thephenomena which take place at that all-importantinterface which is basic to all agriculture — the pointof contact between the soil and the root of the plant.I can think of no subject in the whole realm of soilscience more worthy of the attention of the physicalchemists and the plant physiologists than that of clari-fying the phenomena which take place at this inter-face.

Before taking up the next physico-chemical prob-lem, I must digress for a few minutes to discusscertain ideas about soil conservation and fertilizerswhich are at least somewhat unconventional, whichmay be wrong, but which I think have enough meritto justify our thinking about them for a few minutes.

There is beginning to develop in this country atlong last a much-needed, widespread appreciation ofthe value of the soil to the nation. In our zeal to givethis highly desirable movement all possible momen-

BRAFDIELD : PHYSICAL CHEMISTRY OF SOIL-PLANT RELATIONSHIPS

turn, I sometimes wonder if we have not adopted andspread points of view which may be questionable fromthe standpoint of the long-time interests of both ourcountry and the world.

A very large number of our soil scientists, agrono-mists, and soil conservationists seem to have adoptedliterally and wholeheartedly the so-called "bank ac-count" concept of soil management. I have come tofeel that in the long-time view, especially if we try tosee the problem, not in light of present-day economicconditions merely, but' from the standpoint of whatis the best long-time policy for the peoples of theworld, there is reason to question this philosophy. Inother words, I seriously question that it is wiselong-time agronomic or economic policy to strive toreplace with commercial fertilizers all the elementsthat the harvested crop removes and that are notreturned in crop residues or manure pound for pound.Those who take this view feel that any other actionis inconsistent with sound soil conservation policy. Iam inclined to think, on the other hand, that ourfertilizer reserves, representing as they do the morecostly concentrated materials essential to keep soilsproductive, should receive an even higher priority inour conservation program than our soils. The soil,together with the unconsolidated soil-forming materi-al beneath it, is on the average a rather dilute, fairlystable reservoir of all the minerals needed for theproduction of crops. It is one of the most extensiveand the most common of all the materials used bymankind. Our fertilizer reserves, on the other hand,are from 25 to 400 times as concentrated as our soil

.reserves and are of very restricted distributionthroughout the world. You will recall that Van Hise,one of our pioneer conservationists, placed fertilizers,especially phosphates, at the top of the list of re-sources 'to be carefully conserved. I would like tohave you consider this question: Should we adoptthe balanced bank book concept of soil managementor should we exploit the soil to the limits consistent <with the maintenance of satisfactory yields and effi-cient and economic production using fertilizer onlyin the quantities necessary to supplement the nu-trients that can be supplied by the soil ?

I have had occasion ,the last few years to think alittle about the problem of feeding the hungry peopleof the world. The soil scientist has a very heavyresponsibility in connection with this problem. Ferti-lizers can and should play an increasingly importantrole in many underdeveloped, highly populated sec-tions of the world. But is it probable in the fore-seeable future that it will be economically feasible,even if we had the necessary reserves of fertilizermaterial, to balance the bank account and pay backto the soil, pound for pound, what we take from it inall parts of the world ?

If we are agreed on the importance of conservingfertilizers in our balanced national program of con-servation of natural resources, then it seems to methat the soil scientists and particularly the studentsof the physical chemistry of the soil have the very

important responsibility of developing methods whichwill result in the most efficient use and conservationof these materials.

One might think this statement so obvious thatthere would be no excuse for making it on an occa-sion like this. I have heard at this meeting, however,more than one expression of disappointment in ex-periments which failed to show a profitable responseto the use of fertilizers. If I am correct, this should,under certain circumstances at least, be cause forrejoicing! It has also been pointed out that one ofthe important virtues of the technique of plowingunder fertilizers is that larger quantities can be ap-plied in this way without danger to the crop! It isdifficult for me to reconcile such mental attitudeswith Professor Van Hise's statement!

Practically all available evidence indicates that theefficiency of utilization of phosphatic fertilizers is verylow. Most experiments indicate that the accumulatedrecovery of added phosphate seldom exceeds 25 to30% even in a 3- or 4-year rotation. In the veryinteresting experiments on potato fertilization re-ported by Nelson and Hawkins (pages — to —) atthis meeting, the tubers removed on the average onlyabout 22 oounds of PzO*, per acre per year. Manygrowers in the areas under study are applying tentimes this amount annually and have been doing sofor over a quarter of a century! Under such circum-stances I wonder what percentage of the 22 poundsof P2Og in the current crop was supplied by the lastincrement of 225 pounds added to the soil at plant-ing time ? A profitable return was indicated. At thehigher rates of application i pound of PgOs or 5pounds of 20% superphosphate gave an increase inyield of 10 pounds of potatoes: At the lower rates ofapplication in these same experiments i pound ofPzOs gave 60 pounds of potatoes. What is the wiseconservation policy in cases like that? Many farmerswere unable to get the phosphate fertilizers theyneeded last year. In case there is not enough to goaround, should the man who has used very largequantities in the past and who for that reason couldprobably get along with less or with none, get his"historical" proportion or should it be allotted to thefarmer who can produce the most with it ? Soil scien-tists ought to be able to help give the answers to suchquestions.

During the current sugar shortage a restaurantowner observed that many customers were puttingtwo spoonfuls of sugar in their coffee and leavingabout half of it in the bottom of the cup. He put upa sign advising his customers to "use only one spoon-ful and stir like hell." I think we need to find equiva-lent practices for increasing the efficiency of utiliza-tion of our commercial fertilizers.

Over 100 years ago Liebig criticized the Britishfor robbing the continent of Europe of its bones andthen squandering the manurial equivalent of 3j4 mil-lion men down her sewers to the sea! We are stillequally extravagant. The oriental peoples have a lessextravagant system of conservation, but it too has itsdrawbacks from our point of view. Surely there must

SOIL SCIENCE SOCIETY PROCEEDINGS 1946

be some solution to the sewage problem which isbetter than either East or West has used to date!

The reserves of plant nutrients in the soil beneathour feet are enormous in most of the arable sectionsof the world. For example, there is more potash inthe top .4 feet of soil in the State of New York alone

. than in all the known reserves in the United States.This potash can be purchased more cheaply in theform of New York soil than it can in the form ofmuriate of potash from either New Mexico, France,or Germany. It is already spread. Many soil types, ifproperly managed, can supply over 300 pounds ofpotash per acre per year to certain crops.

These soils are frequently underlain with greatdepths of unconsolidated material which is oftenhigher in potash, phosphorus, and lime than the sur-face soil. I think we need to explore ways and meansof exploiting these subsurface reserves as those inthe surface soil become exhausted instead of tryingto balance the books completely by the purchase ofcommercial plant food. There are several methods ofapproach which should be explored.

The topography of these soils is usually rolling.Experiments on similar types of soil indicate thatwith commonly used rotations and a sensible, practi-cal type of contour cultivation the time required toerode away the surface 6 inches of soil can easily beextended to from 200 to 400 years. Should we at-tempt to extend it any more than that ? Do we wantto prevent erosion or do we want to control erosion?Is there an optimum degree of erosion which weshould first determine and then strive for in develop-ing soil management systems? When I think of thisquestion, I nearly always recall a statement made byDoctor Marbut years ago while he was conducting afield trip in Pennsylvania: "Erosion keeps soilsyoung." We want, it seems to me, neither the oldhighly leached soils, often with impeded drainage,which tend to develop under many circumstanceswhen erosion is restricted too much, nor the infantsoil which results when the soil is eroded away fasterthan the subsoil can be converted into soil by thesystems of management followed.

It seems to me that it is reasonable to think thatthe proper objective of the soil scientist is to find aproperly balanced middle course between these ex-tremes. It will vary with the soil, the cropping sys-tem, the price of fertilizers and lime, and the generalprice level. The soil scientists should supply theanswer.

Before we can supply the answer we need to knowmuch more about the physical chemistry of weather-ing. Why are certain clays formed in certain circum-stances and other clays under other circumstances ?Millions of tons of nutrient elements are lost eachyear in the drainage water. The evidence availableindicates that the calcium lost in this way is frequent-

- ly three to five times as-great as the amount removedby the crop. The amount of potash lost in this wayis often of the same order of magnitude as that in theharvested portion of the crop.

It seems to me that it might be more economical toprevent or at least to reduce these losses to a mini-mum than to let them find their way to the ocean,and then in some distant millennium, mine them,process them, arid return them to the soil in com-mercial form!

If these problems are to be solved we need to paymore attention to the possible role of the subsoil incrop production. Many soil scientists have, in myopinion, tended to underestimate the potentialities ofthe subsoil in supplementing the surface soil. As greatan authority as Sir John Russ'ell has stated that, "Itis well known that only the top 6 or 8 inches of soilis suited to plant life and that the lower part, or sub-soil, plays only an indirect part in plant nutrition. Weshall, therefore, confine our attention almost exclu-sively to the surface layer." The great majority ofsoil scientists have consciously or unconsciously fol-lowed this same line of reasoning. Practically all ourefforts at estimating the capacity of a soil to supplynutrients are based upon studies made on the sur-face 2,000,000 pounds of soil. We know, on the otherhand, that crop roots commonly extend from 2 to 10feet into the soil and that they exhaust the moistureto that depth under certain circumstances. Is it likelythat there is a mechanism in the subsoil roots whichenables them to take up the needed water and to ex-clude the needed nutrient elements ?

We know, that we can get satisfactory growth ofmany crops from very dilute nutrient solution pro-vided the volume of the dilute solution is greatenough or is renewed at a sufficiently rapid rate. Deepsoils are traditionally productive and shallow soilsare traditionally unproductive. I am inclined to thinkthat some of the difficulties we have had with chemi- 'cal procedures for estimating the fertility of soils aredue to the fact that we have confined our attentionalmost exclusively to efforts to measure the supplyper pound of surface soil. In other words, we havebeen attempting to measure what may be regardedas the intensity factor of soil fertility and have dis-regarded the capacity factor. The actual capacityshould be the product of an intensity factor, ex-pressed if you wish, as weight available per unit ofweight of soil, by a capacity factor, which will takeinto account the actual volume or weight of soilwhich the crop is able to exploit.

I shall always treasure the only visit I ever hadwith Milton Whitney, for so many years Chief ofthe United States Bureau of Soils. Dr. Frank- Parkerand I visited him in his office in Washington just afew months before he died. Our careers were juststarting; his was rapidly closing. He had just had areport from one of his staff who had just returnedfrom the tropics and had told Doctor Whitney of theevidences of active weathering and high biologicalactivity at great depths in these soils. Doctor Whitneyadvised us to pay more attention'to what is going onin the subsoil. I pass his advice on to you. I am in-clined to think that in many locations it is economical-ly feasible to increase the depth of soil which can beexploited by crops.

BRADFIELD: PHYSICAL CHEMISTRY OF SOIL-PLANT RELATIONSHIPS 7

To learn how to unlock the practically unlimitedreserves of practically all plant nutrients, except ni-trogen, which lie beneath the soil is a task that willrequire men skilled in many different sciences. Inmany cases the soil will have to be drained to agreater depth. Aeration will have to be improved.Conditions will have to be made more favorable forflora and fauna which can gradually penetrate the soilto greater depths. All the factors mentioned abovewill need to be brought to interact to produce a betterstructure in the soil. The physical chemist will haveto work closely with both the soil mineralogist andthe soil microbiologist if he is to develop a real un-derstanding of all the phenomena that .are involved.

Even the tools of the physicist and physical chemistare becoming so complicated and specialized that it isoften necessary for one to spend long periods in be-coming proficient in their use. In many cases at leastit will probably be more fruitful for him to devotehis energies to applying the techniques he has mas-tered to a variety of problems, no one of which hewould be capable of investigating alone. Already soilsmen are using X-ray diffraction apparatus, electron-microscopes, radioactive isotopes, spectographs, pol-arographs, etc. Unlike the analytical balance, wheat-stone bridge, or potentiometer, these are highly spec-ialized devices. They are capable .of yielding valuableinformation in the hands of the skilled operator. Evenin cases where the routine use of the equipment isfairly simple and can be learned in a few days, theinterpretation of the data obtained requires a longapprenticeship at specialized study.

I can see no alternative to the development of aresearch team of specialists if many of the more in-tricate problems of soil science are to be solved in areasonable length of time. An isolated physicist workring alone might conceivably, I suppose, develop anatomic bomb in a lifetime, although I think it highlyimprobable. A properly organized research team withadequate support did the job in three years!

I do not mean to imply there is no place for the"lone wolf" or the isolated genius in his garret labo-ratory. There is a place in this world for all kinds anddescriptions of scientists. I feel, however, that theproportion of problems that can best be solved by thesingle isolated scientist is becoming smaller and thatthe more intricate problems which require the team-work of a group of specialists are becoming morenumerous.

The type of teamwork I have in mind may takevarious forms. For certain types of problems, it maybe formed completely from men in the same depart-ment, by the cooperation, for example, of the soilchemist with the soil physicist, the soil bacteriologist,and the specialists in soil fertility and morphology.In the case of other problems, it may involve co-operation between different university departments,for example, the cooperation between the soil physi-cist in the department of agronomy, a pomologist,and a plant physiologist. In still other cases, it maytake the form of cooperation between specialists in

the same field, but working in different institutionsin a given region on a problem that is common to thedifferent states in" that region. We have one excel-lent example of the mutual advantages that can beobtained in such regional teamwork in the study ofthe residual phosphorus content of the heavily fer-tilized potato soils of the eastern coast from Maine toAlabama. Because of restrictions which exist in manystates on travel outside the state by the members ofour state agricultural experiment stations, such co-operation has been difficult in the past. With thepassage of the new Flannagan-Hope Bill, such re-gional cooperation is not only made possible, it iseven made obligatory.' A certain proportion of thefunds of both the states and the United States De-partment of Agriculture has to be spent for coopera-tive research of a regional nature.

During the war there was some very effective team-work between agricultural specialists from differentcountries on the production of certain crops whichwere of critical value in connection with the war. Ahigh percentage of the men who have been engagedin such activities see great possibilities for the fur-ther development of such cooperative agriculturalresearch between our country and our neighbors,particularly our neighbors in the tropics and otherareas which are capable of producing crops which werequire but cannot grow satisfactorily within ournational boundaries. The Food and AgricultureOrganization of the United Nations, if it is to fulfillthe objectives for which it was created, will have todevelop international teams for the solution of vari-ous types of agricultural problems, and of all theseagricultural problems those which will probably ap-pear in the position of highest priority on the list willbe problems which will call for the skill of men trainedin the physical chemistry of the soil.

How will this emphasis on teamwork affect thequalifications which administrators will look for inselecting the personnel required to do the job? I amquite sure that in addition to the customary qualifi-cations relating to technical competence, whichstandards will unquestionably become higher andhigher as time goes on, even more emphasis will beplaced upon personality, good character, and the abil-ity to get along well with other people. >

The quality of our field experiments in soil sciencehas greatly improved in the last decade, largely as aresult of the development of improved statisticalmethods. As I study the fesults of many of theseexperiments, I often have the feeling that many ofour research workers feel that their job is done whenthey complete their analysis of variance and establishthe odds of significance for their experiment. This isoften done even in cases where the variation in yielddue to factors which are uncontrolled or are unknownis of the same order of magnitude as the factor orfactors being studied. It seems to me that instead ofstopping with the statistical analysis, we should re-gard it as a guide to unsolved problems regardingthe factors in the environment which are exerting

SOIL SCIENCE SOCIETY PROCEEDINGS 1946

an important influence upon the growth of the crop.In such a study, I feel the soil physical chemist canbe of great help to the field worker.

When .1 look over a volume of our PROCEEDINGS,or any similar volume of current contributions to ourliterature, I am always impressed by the fragmentarynature of a high percentage of the contributions. Eachpaper may, and probably does, contribute its grain oftruth to our immense storehouse, but it is becomingincreasingly difficult to trace the relationship of thesevarious fragments to each other. The classical ap-proach to agronomic problems was to keep all factorsof the environment constant, except the one understudy, and to vary it systematically. Even a super-ficial analysis of the cycle of changes which go tomake up the environment of the growing plant willindicate that this classical approach is highly arti-ficial. If we are ever to obtain a satisfactory under-standing of the factors which are limiting the growthof our crops under natural conditions, I am convincedthat the physical chemist and the plant physiologistare going to have to leave their laboratories and goout into the field and apply their skills to followingthe minute-by-minute changes which are taking placein all the principal factors which go to make up the

environment of the growing crop. I believe that thetools for doing this job can now be fashioned. Weneed only to get them together and provide the skilledmen to operate them.

I seriously doubt that it will ever be possible forus as individual specialists to hope to unravel thesecomplex relationships in any adequate way. I am con-vinced we can make more progress if we form a re-search team with, our colleagues and make a moresystematic, more complete, and better coordinatedattack on these problems. With the physicist, thechemist, the microb.iologist, the plant physiologist,and soil scientist joining hands, studying the samesituations, each bringing his own special skills to.bear on the problem, counseling and criticising eachother, with the proper type of personalities, training,and leadership, I cannot but feel that for manyagronomic problems at least this method of approachoffers a better chance at success than the policy ofrugged individualism still common in so many insti-tutions in which each specialist has his own plot ofground, raises his own corn or alfalfa, observes thething that happens to interest .him most at the mo-ment, and in the end excuses his lack of results be-cause "there are so many factors entering in."