«m .L (".K \ ' ‘d 4., w *P n‘ ‘A .“r “‘1‘ ‘\ “7" l5), '5) ~_a wavy» .- % ‘2’. '13? v r .. TH E535 V. ms BASE-EXCHANGE CAPACITY OF THE ORGANIC AND INORGANIC FRAC- TIONS OF SEVERAL PODZOLIC SOIL PROFILES m BABE-HCHANGE CAPACITY OF THE ORGANIC AND INORGANIC FRAC- TIONS OF SEVERAL PODZOLIC SOIL PROFILEB AMSIS summon to th. Graduate 361106]. of man-1m State College of Agriculture and Applied Science in partial fulfilment of 1th: roqniromnta for the degree of MASTER OF SCIENCE Department or .8011: 1940 THES‘S‘ A0315 O'LEDGW T For the many helpful euggoatione and criticisms receiv- ed during the progress or this investigation the writer is very grateful to Dr. W, S. Gillan, under whose general super- vision the work was done. The writer aleo viehee to thank . Dr. C. B. Spmay for his kind adviee during the progreu of this study. 1. 8. 3o 4. 5,. 6. 7. 8o 9. TABLE OF OONTNTS INTRODUCTION REVIEW or LITERATURE DESCRIPTION or SOILS STUDIED DISTRIBUTION ON THE SOIL SITES ANALYTICAL PROCEDURE DISCUSSION mm BIBLIOGRAPHY MENDII OOGNP 15 33 35 IHTRODUOTIOfl It is a well known fact that both the organic and in- organic portions of the soil play an important part in the base-exchange reaction. Considerable work of the past dealt either with the inorganic and organic portion of the soil as a whole, or Just the mineral fraction. The effect of different fertilizer treatments and var- ious farming practices upon the exchangeable bases has been studied extensively. the ability of a soil to release certain ions readily and to retain other ions firmly, has been inves- _ tigated rather thoroughly. The total analysis and base-exchange capacity of a hump her of soils at different depths have been reported. But un- til recent years little work has been done on the base-exchange capacity of the organic matter of the soil, and the importance of this fraction in the base-exchange reaction has not been theroughly investigated. The study of various types of decomp posing organic materials and their base-exchange capacities has been an expanding study the last number of years. However, as far as the writer is aware, no one has attempt- ed to determine the base-exchange capacity of the organic mat- ter in the different soil horizons. Therefore, in this paper, an attempt was made to gain some further knowledge regarding the base-exchange capacity of the organic matter in the differ- ent soil horizons. It was the object of this investigation to determine the base-exchange capacity ofgthe organic matter in the A1, 53, 31, 3. 33, and c horizons of six soil profiles collected in Michigan. The profiles were also analysed for exchangeable calcium and magnesium. The effect of pH upon the base-exchange capacity of each soil was also studied, by using ammonium.acetate ad- Justed to a pH of 7.0 on one set of samples, and ammonium.ace- tats adjusted to the pH of the soil, on a second set of samples. REVIEW‘QETLITERATURE Way, (16)1 in the year 1853 first discovered that soils had the power to exchange bases. Gedrois (5) in some of his earlier writings conveyed the idea that although the organic portion of the soil did have some power to exchange bases, it was practically negligable in comparison to the inorganic por- tion. However, in later years, Gedrois (4) revised his ideas and suggested that the organic portion of the soil may have an important part in base-exchange and that the base-exchange ca- paeity of the organic matter may even exceed that of the min- eral portion. Beyer (2) found that 50 to co per cent of the total base- exchange capacity of a soil could be attributed to the organic portion. Mitchell (10), found that the organic portion of the soil constitutes 41 to 65 per cent of the total base-exchange capacity. Olson and Bray (18), in their study of Illinois soils, found that the base-exchange capacity of the organic portion varied from.0.6 to 16.5 millicquivalents constituting from 6.8 to 43.4 per cent of the total base-exchange capacity of the soils. In their investigation the destruction of the Wi‘ri 1Indicates literature cited._ 3. basepexchange capacity of the organic portion was accomplished by using a single cc ml. treatment of 15513303. Although there are many conflicting opinions as to methods of destroying or- ganic matter, Alexander and Byers (1), after a critical lab- oratory study of methods of determining organic matter, came to the conclusion that 3303 may be used to determine the amount of readily exidisablc organic portion of the soil, but it should not be used in determining the total amount of organic matter present. {Meaeorge (7) concluded from.his data that there was a wide variation in the base-exchange capacity of lignin-likc bodies in different soils, and also that it was by no means a constant quantity, for in all cases these exchange compounds were able to undergo further alteration, probably a hydrol- ysis, which increased, or built up their base-exchange capaci. ties. He found that lignin from.different soils had a base~ exchange capacity that ranged from 38 to l7azmilliequivalents per 100 grams. Ligno-humatc material showed a:much higher and more constant capacity, ranging free 581 to 451 milliequiva- lento per 100 grams. He also found a close correlation between the total base-exchange capacity and the carbon content of the soil, there being an increase of 35 milliequivalents base-ex- change capacity for each 10 grams of carbon in the soil. Mitchell (ll) pointed out that the presence of organic matter increases the base—exchange capacities in the surface horizons. Miller, Smith, and Brown (9) showed that mature plants vary greatly in their base-exchange capacity. It was also shown that the increase in base-exchange capacity can be 4. attributed, at least partially, to the increase in the lignin content of the decomposed.matcrials. However, the increase in haseeexchange capacity was so much larger than the increase in lignin, it would scam.that the absorptive capacity Of lis- nin has been increased during the decomposition. tremor (14) found that the humus of the soil has a base- exchange capacity of 151 millicquivalcnts per 100 grams, shilc the clay fraction has only adzmillicquivalents per 100 grams or about one-sixth that of humus. Mitchell (ll) found that the base-exchange capacity in general showed no marked difference throughout the different horizons of the same profile. In most cases it follows the clay content fairly closely. mattson (8) found that clay had a base-exchange capacity of 16.4 to 110.8.milliequivalents per 100 grams of clay. Kerr (6), in his review of the literature, points out that it is evident that there is a lack of unanimity concern» ing the true nature of the mechanism.involvcd in the base-ex- change reaction. One school favors the theory that the phenn omcnon is one of adsorption attributable to the highly dis- persed condition of the soil colloids. Another group believes in the chemdcal idea, because it has been demonstrated that many of the characteristics of the reaction, point to true chemical forces as being the controlling agencies of the pro- cess. The great speed of the base-exchange reaction led God- rois to believe that it was a non-chemical reaction. A review of the literature has yielded only fragments of data as to the base—exchange capacity of the soil in different 5. horizons, and the percentage that is due to inorganic and the organic matter. rho lack of concrete data of this na- ture led to the study of this problem. DESCRIPTION or THE sons STUDIEDI This study was confined to the podzolic soils of the loser peninsula of Michigan. Representative samples of six different profiles developed under the prevailing humid cli- mate from various parent materials, and under various drain- age conditions were obtained frmm the locations indicated in figure 1. The numbers refer to the profiles described below. 1. Isabella.loam. This is a well drained soil devel- oped from caleaerous, morainic drift under a hardwood forest in which beech, maple, hemlock, ash, and basssood were the dome inant species together with a few scattered white pins. the forest floor is covered with a 8 to 4 inch litter of decompose ing'enddecaying leaves which overlie a relatively homogenous layer of black granular, neutral to slightly alkaline, organ- is material ranging'frem.i to 1 inch in thickness. underly- ing this is a s to 6 inch layer of harsh, platy, ashy-gray loamy sand to sandy 1oam.which is sometimes acid in reaction, and somewhat stained at the top by infiltering organic matter. Below the podzolized layer, 10 to 14 inches of transitional sandy loam.or loam grade into reddishebrown, aeid, highly struc- tured sandy clay. This layer is characterized by a nut or block-like structure, the surfaces of the blocknlike structure, 1Acknowledgement is made to MI. a. 3. Mick for his description of the soil profiles used in this study. MICHIGAN (AK: 5 UPERIOR ONTONAGON coca: MA RQU ETTE .\ \ CHIPPEWA ANTRJM OTSEGO MONTGALM GWIUT SAGINAW cum: me srcuun ALLEGAN OAKLAND WY EATON 'NGHAM WNW CALHOUN JACKSON LENAWEE Figure 1. Distribution of the soil sites sampled in this .tua’e 7.- ths surfaces of the blocks being covered with a dark brown coating and many minute roots. In the lower part free car- bonates are not infrequently observed. IMessive, calcareous, pinkish or reddish-brown till clay is encountered at depths ranging between 8 and 6 feet below the surface. 8. Selkirk loan. This is a well-drained heavy textured soil which developed on the clayey calcareous lake plains un-' der a mixed forest of pine and hardwoods. from the surface downward Selkirk loam consists of a dark colored humus layer from 1 to 3 inches in thickness; 4 to 8 inches of ashy-gray fine sandy or silty loam; pale yellowish-brown often slightly mottled sandy loam.to clay loam, 3 to 8 inches thick; and fin- ally impervious pale reddish-brown clay. The first three lay- ers may sometimes be acid but the heavy subsoil is alkaline and the sub-stratum contains a high percentage of carbonates. 5. Rubicon sand. This is a well-drained, pervious soil of the dry pine plains. l to 3 inches of litter accumulates under a virgin cover of red and white pine. L.one-fourth inch humus layer is underlain by the chaoteristic ashy-gray podzol- ised sand which ranges between 3 and 8 inches in thickness. This layer in turn overlies and grades into a pale yellowish brown loamy sand frames to 6 inches in thickness, slightly indurated in places. !hs substrate consists of pale yellow, loose, previous sand which extendszmore than 7 or 8 test he- los the surface. a. Ogemaw sandy loam. Ogmmas sandy loam.is a ground water podzol of the poorly drained pine plains. The surface is characteristically rather mucky under a relatively deep 8o accumulation of litter; this soggy humus layer, a or 3 inches thick overlies 4 to 3 inches of conspicuously white sand or loamy sand. Abruptly underlying the leached layer is a dark coffee-brown heavily indurated, sandy shard pan" which in places may be as much as 18 inches thick. Irhrough a thin transition layer the brown color rapidly changes to the drab, dingy gray of waterlogged sand. at a depth varying between 5 and ,5 feet, heavy impervious locustrine clay is encountered, rho sub soil contains a snail percentage of carbonates. 5. Kalkeska loamy sand. This soil developed under a hardwood forest of beechgmaple, and hemlock on the dry sand plains. Ihe surface litter decomposes rapidly to produce a thin, dark-brown, neutral, humus layer which overlies a to 4 inches of a dark gray, lousy send. This layer grades down- ward into a to 5 inches of ashy-gray loamy sand which may be acid in reaction. Underlying this podosolised horizon are 4 to 10 inches of dark coffee-brown loam sand which often is slightly indurated. This brown color rapidly fades so that betwoen 18 to 84 inches the pale yellow, pervious, sandy sub- stratum.is encountered. 6. mt loam sand. This is a light textered soil which is developed beneath a hardwood cover in the alkaline, sandy, morainio drift. Under a moderate accumulation of litt- er and a thin, neutral to slightly acid grayish-brown hunms layer, are 3 to 3 inches of dark-gray stained loan sand to sandy loam which grades into the harsh, platy, compact ashy- gray leached horizon. This podsol horizon is acid in reaction and ranges between a and 6 inches in thickness. It is under- lain.by e to 10 inches of brownishwyellow, acid, loamy sand which.in turn grades downward into the sandy and gravelly par- ent drift material. ANALYTICAL researches .ghe soil samples were collected by horizons and allowed to air dry. They were then screened and ground to pass through a scive containing 0.84:mm. openings. The soils were thorough-‘ 1y mixed, the percentage moisture was determined and the re. maining portion of the sample was reserved for other determin- ations. _0rganic matter was calculated by heating the equivalent of a two gram sample of water-free soil and weighing the amount of carbon dioxide liberated. The method.employed consisted of heating the sample, after it had been treated with small quantities of.manganese dioxide and crystaline alumina, in an electric furnace at 950°C. and passing a stream of oxygen through the soil. The organic matter was completely destroyed in less than 10 minutes of heating. The carbon dioxide was collected in a tube of ascarite which was weighed before and after it absorbed the gas. The increase in weight was found and the organic matter was calculated by multiplying the weight of the carbon dioxide liberated, by the factor 0.471. This factor is derived by the following method: Boil organic matter is approximately 58 per cent carbon. therefore per cent a x 1.788 a per cent organic matter. m u I 1.728 . 0e‘71 10. .EE:_£9§i; “71 "100 = per cent organic matter or the 39 samples studied, seven contained free calcium carbonate. When organic matter was determined in the presence of calcium carbonate by the method Just described, the sample was heated above the decomposition point of this substance. Therefore the following reaction took place cacos m2) «0+ 003 and.the carbon dioxide from the calciun.carbonate collected in the ascarite tube with the carbon dioxide from the organ» is matter. In order to correct for the percentage of carbonate present, the amount of carbonateslwere determined by the Scheibler method. A two to five gram.sample of soil, depend- ing on the carbonate content, was treated with 20 per cent uni and the volume of carbon dioxide liberated sas determined sith Scheibler's apparatus. The volume of carbon dioxide was then corrected to standard conditions and the weight calculat- ed from the volume. When the weight of carbon dioxide from the calcium.carbonate was determined, and that weight subtracted from the weight of carbon dioxide liberated by using the comp bastion furnace, the resultant figure was due to the carbon dioxide from the decomposition of the soil organic matter. The pfl:of the soil was determined electronetrieally by means of the glass electrode. d.small crucible was filled .v. WTT v__,.., 1It is realized that not all of the carbonates present in the soil are combined with calcium, however, since the rel- ative percentages of calcium and magnesium carbonates pres- ent had no particular bearing on this problem, they were all reported as calcium carbonate. 11. with soil to within about one-fourth inch of the top and was saturated with distilled water. The samples were then left standing overnight to come to an equilibrium and the pH was determined the following day by using the Beckman pH meter. Base-exchange Determinations the apparatus used in the base-exchange studies was sim- ilar to that deseribed by Russell (lb). mnty-five-gran can» plea of soil were used. The‘soil was past“ firmly into the percolation tubes as shown in figure 8, so that the leaching solution cans in contact sith the entire sample of soil. figure 3 f ———>--fl 4% /Porcelain Plate .._— quarts Sand Ca - ' 0 .‘éfr—soil :‘37 ’o" 4' ’0 "'0'. 'o, , 0i, l I ’ 0 I 5 I o ’ 0 ’ I I I {If —— quarts and Filter Paper 18. Normal ammonium acetate adjusted to a pH of 7.0 was used as the leaching solution. By using this extraction apparatus, it required about eight hours for the 500 ml. of ammonium ace- tate to pass through the soil. The leaehats was then reserved for the determination of exchangeable calcium and magnesium. Determination of the Base-exchange capacity After the soil was leached with the ammonium acetate, the excess ammonium acetate was renewed from the soil by pass- ing :00 ml. of 50 per cent methanol through the sample. The ammonia that remained in the soil after this treatment was in the exchangeable four. The amonia that saturated the soil complex was then re- moved by passing 250 ml. of normal calcium acetate solution through the soil. The solution of calcium acetate and ammon- ium acetate was collected in Kieldahl flasks. The solution was then treated with 0.5 m. of tannic'acid, to prevent foam- ing, and 8 ml. of so per cent sodium hydroxide to make the sol- ution alkaline. Two hundred ml. of the mixture was then dis- tilled over into as ml. of a 4. per cent solution of boric acid. 151/10 301 was used to titrate the caesium liberated, bran-phen- ol blue being used as the indicator. The results were then converted to nilliequivalents per 100 grams of waterefree soil. Determination of Exchangeable Calcium lrho ammonium acetate leachate was evaporated to dryness on the steam bath and the residue was then treated with 30 per cent hydrogen peroxide until all of the organic matter was 13. destroyed. The residue was then taken up in 200 ml. of dis- tilled.water, brought to a boil and 10 ml. of 10 per cent E3401 was added. Then 80 ml. of n/z (“34’80204 was added and the calcium was precipitated as Cacgog. After the precipitate was eovered and allowed to digest, a drop of (NH4)3 czo“was added to insure an excess of (unp)acac4 in solution. ‘Ihen the «one; was digested it was filtered quickly and washed free of (NH;)zczc“.1.h boiling water. The filtrate was reserved for the l3;determination. When the filtrate no longer gave a test for oxalates, the filter paper was broken and the 0&0304 was washed into a clean beaker. The beaker now contained the ' cécgo, precipitate in about zoo ml. of water. The cacao; was dissolved in so ml. or 18 n 3330., and brought to a boil. While the solution was still hot it was titrated.with.H/1O KMDOg sol- ution. Next the filter paper was added to the beaker and the final and point determined. 'me calcium was calculated from 'the Id. of KMh04 reduced. Determination of uchangeable Magnesium The filtrate, from the calcium determination was adjust- ed to about 250 ml. The solution was then acidified with 4 ml. of con. 1101. Then 15 ml. of a freshly prepared 10 per cent solution of dibasic ammonium phosphate was added and the solu- tion was cooled to 80°C. 50 ml. of con. man was then slow- ly added with constant stirring. Phendphthalein was used as an indicator and when a pH of 9.0 was reached, the solution was stirred vigorously until the magnesium precipitated, the remaining volume of the NH‘OH was then added. The bankers containing the precipitate were allowed to stand in a cool 14. place over night. The precipitate was filtered on No. 43 What- man filter paper and washed with 10 per cent men. The mg.- nesiuleammonium.phosphate was then ignited at 900°C. to con- stant weight. During the ignition, the following reaction took place: a MgNH‘PO‘J ago 32932; m3+isnzo+nggr307 and the nggraoq was determined gravimetrically. ‘Dstermination of the Base-exchange Capacity of the Mineral Portion of the Soil The method used for determining the base-exchange capa- city of the inorganic portion of the soil was that proposed by Mitchell (8), who found that ignition at 350° to 400° C. for seven or eight hours, produced a well oxidized sample, but did not destroy or change the baseoexchange capacity of the in- organic material. 4.85 gram sample of soil was ignited at 400°C. for seven hours. When cool, the sample was placed in the percolation tube and the base-exchange capacity was determined. Then the difference between the base-exchange capacity of the original soil and that of the sample in which the or- ganic matter had been destroyed, represents the base-exchange capacity of the organic matter in 100 grams of soil. The base-exchange capacity of the organic matter was then converted to the 100 gram equivalent basis by the formula. Exchange capacity 100 3. due to organic matter Base-exchange capacity . ressed in M33. : For 100 grams of or- per cengiorganic matter'” ' ganic matter. 15. The effect of'Varying pH of the Ammonium Acetate Solu- tion on the Base-exchange Capacity of the soils The object of this part of the problem.wns to extract the bases and determine the base-exchange capacity of a soil with the ammonium.acetate adjusted to the same pH as that of the soil. The analyses were determined in the same manner as previously described. DISCUSSION The graphs in figure 3 show the variation in the base- exchange capacity in the different soil horizons; also the amount of the base-exchange capacity due to the organic frac- tion, and the amount due to the inorganic fraction of the soil. When the base-exchange capacity is relatively large as it is in the B and C horizons of the Isabella and Selkirk loans, and the C horizon of the Ogemaw sandy loam, it is due almost entirely to the inorganic fraction of the soil. The particular horizons mentioned are composed of a very fine textured clay, thus those horizons have a large specific sur- face. It is a well known fact that a large specific surface tends to increase the base-exchange capacity of a soil. There- fore, it is to be expected that in these heavy textured soils, a large base-exchange capacity should be found. In the sandy textured soils; Rubicon sand, Kalkaska loamy sand, and Emmet lomny sand, the inorganic fraction of the soil shows a very low base-exchange capacity, especially in the lower horizons. this can be attributed largely to the sandy texture of the soil which has a small specific surface as compared to clay 16. Base-exchange capacity of various horizons expressed in milliequivalents per 100 grams ot~oven~dry soil. M.£. Fig. 3a Isabella loam £O*p TOtal Men. 33’.“ /s + exchange capacity MtE. Base-exchange /‘ - .Capacity in Miner- al Portion If. M33. Base-exchange capacity in organ- L2 is matter ID- 8 . 6 . f- .. 0 n J! ILB. Fig. 5b 801k1rk loan l7. Base-exchange capacity of various horizons expressed in milliequivalents per 100 grams of oven-dry soil. Fig. 5c Rubicon send as fi—F L . 2 3’ 6" Total 16.3. Base-exchange Capacity _____ _ ms. Base-exchange Capacity in Mineral Portion —--— MJ. Base-exchange Capacity in Organic Matter M.::. Fig. 5d ogemaw sandy loam 6 .. 4:- , 2+ \\ /”\‘ N," "$4: _____ ,x’ ‘\‘ A: I As I 8 . I I C : ? 18. Base-exchange capacity of various horizons expressed in milliequivalents per 100 grams of oven-dry soil. Fig. 3e Kallcaska loamy sand 6 +- 4 .- 2 .. a I I c . .i “I a! Total 191.3. Bess-exchange Capacity ....... LE. Baseeexchange Capacity in Mineral Portion -—-— M.E. Base-exchange capacity in organic Matter :‘E' Fig. 31' must 10m sand 19. soils. It can be seen in figures 3a and 3b that the organic matter in the calcareous soil1 horizons, Bl, Ba, and c, usually show a greater base-exchange capacity than the organic matter in the non-calcareous soil horizons. This is also shown by horizon c. figure 3d. This is to be expected because of the fact that there is usually a larger percentage of organic matter present in the lower horizons that contain cases than the corresponding horizons in other profiles that do not con- tain cocoa. This is accounted for by the fact that when col» loidal humus moves downward through the profile, it is fixed when it comes into contact with Ca003. However, when the hump us.moves downward in a profile that does not contain Ca003, not as much of the humus will remain in the profile because there is no Ga003 nor need; to fix the humus. Ieksman (15) states that calcium is present in humus only in an adsorbed condition, but does not form any salts. Hnmus is fixed in the presence of calcium and when this base is removed, the humus is readily lost, hence the total base-exchange capacity of the soil organic matter decreases. In.most cases it is true, that the percentage of organ- ic matter is higher and has a higher base—exchange capacity in the horizons that contain calcium carbonate than the cor- responding horizons of other profiles that do not contain calcium.carhonate. However, there may be other factors more powerful in influencing the movement of organic matter in the soil profile than calcium.carbonate, such as water, soil tex- 1By a calcareous soil is meant one that :hows effervescencefi when treated with a 20 per cent solution of HCl. BO. ture, and the quantity and nature of the organic matter in the top horizons. Gedrciz (3) noted that the soil-adsorbing complex consists of both organic and inorganic soil constituents; the greater importance of one or the other in this process varies with different soils and with different horizons of the same soil. the organic fraction of the surface horizon of all soils used in this investigation possessed a greater base-exchange capacity than the inorganic portion of that horizon. Except in the zone of accumulation, it is noted that the percentage of organic matter and the base-exchange capacity of the organ. is fraction decreases with increasing depth. All soils ex- cept the heavily leached Rubicon sand tend to show that there is a zone of accumulation in the B. horizon. It can be seen that the increase in the base-exchange capacity in the B hor- izon of the Ogemaw sandy loan, and the 31 horizon of the Kel- kaska loamw sand, and Emmet loamy sand is due mainly to the accumulation of organic matter in the horizon, figures 3d, 3e, and 3f. However, as previously explained, most of the base-exchange capacity of the heavy soils is due to the in- organic fraction. is was pointed out in the review of literature, several warmers reported that the percentage of the base-exchange ca- pacity, due to the organic matter in the soil horizon, varied widely. The graphs given in figure 4 show the percentage of the base-exchange capacity due to the organic portion of the soil and the percentage due to the inorganic portion. In the Isabella.(nig. 4a), A1 horizon, the organic matter is the pre- 21. Base-exchange capacity of the inorganic and organic soil fractions expressed as percentage of the total base— exchange capacity, IOrganic D Inorganic Per Per cent cent lo Mo 0 F 113. 4a * fig. 4b .90 . Isabella loan 90 . Selkirk loan 80 - F — 80. T 7.. T 60 _ :0 9‘0. 30 . .20. lb. 0 8‘ C A, A: 8: 3,, c per Port can ,3?“ m. 0' Fig. is 113, 4,4 90 _ Rubicon sand 90 _ Ogemaw sandy loam W 32. Base-exchange capacity or the inorganic and organic soil fractions expressed as percentage of the total base- exchange capacity. I Organic D Inorganic Par cent /00 _ 70 - 80- 70 . 60 50 4'0 . .70 - 20 IO 0 Par cent /00 70 - 30 7o . so - 50 4m 30 _ 20 - IO- Fig. 4e Kalkaska loamy sand 4r Emmet loamy sand .9, a. c 25. dominant traction, however, as we go deeper into the profile, the inorganic traction possesses a greater capacity for ex- changing bases relative to the organic fraction of the soil. This is to be expected since with increasing depth percentage organic matter decreases. The Selkirk (Fig. 4b), is some- Ihet similar to the Isabella; the organic.metter in the A1 and £3 horizons constitutes over 50 per cent or total base-ere change capacity, thereas in the 31, 38' and c horizons, the inorganic portion is the dominant traction in producing the base-exchange capacity. The organic matter is the predominant traction in the i1 horizon of the Rubicon sand, (318. to). In the L3 and 31 horizons, the organic traction contributes about 56 per cent the total baseeexchange capacity. However, in the 33 and c horizon, the inorganic fraction contributes the great- er portion of the total base-exchange capacity. In the Ogemae sandy loam (Fig. 4d), the greater portion of the base-exchange capacity or the A1 horizon is due to organic matter, Ihile in the ‘8 horizon about one-half of the base-exchange capacity is due to the organic matter and the other half due to the inor- ganic matter. In the B horizon the effect or the organic mat- ter is very predominant, as we might orpeet, since this is the coffee-brown layer and contains a considerable amount ct humus. In the c horizon, the inorganic matter is dominant, since the organic matter content is low and the parent mater- ial is sandy. In the Kalkaska loamy sand (Fig. 4a), the or- ganic matter plays a dominant role in the base-exchange ca- pacity or the ‘1' A3, 31' and Ba horizons while the inorganic fraction is dominant in the c horizon. In the Emmet sandy 34o loam.(r13' 4f), the organic matter in the A1 horizon is the predominant fraction, however, in the A3 horizon we find about one-half of the base-exchange capacity due to the inorganic matter and about one-half due to the organic matter. In the Bl horizon there is a layer of accumulation of organic matter and, therefore, the greater portion of the base-exchange ca- pacity is due to organic matter. However, in the Be and c horizons, the inorganic matter dominates. All of the figures so far discussed clearly illustrate the greater effect of organic matter content on the base-ex- change capacity of light-textured soils as compared to heavy textured soils. Table l. The percentage of the total base-exchange capacity that is due to the organic matter in the various soil horizons. Percentage of the total base-exchange capacity Horizon due to the organic matter A1 63s. - 8608 A3 41.7 ’ 61 e9 Bl 89.4 - 84.8 - 33.3 C 16.3 The base-exchange capacity of the soil organic matter was converted to milliequivalents per lOO grams of air dry organic matter. The results are shown in figure 5. It can be seen that there is a wide variation in the base-exchange capacity of the organic fraction in the different soil pro- files, and also between horizons within the same profile. It is apparent that the base-exchange capacity of the organic fraction of the Selkirk and Isabella soils is much Bess-exchange capacity of the soil organic matter at various depths expressed in milliequivalents per 100 grams of organic matter. Fig. 5a Isabelle lees! Fig. 5b Selkirk loam ‘93. _—7 Isle $00 . J00 r __ 950 L “0* i‘O . #00 r 1 0 3.50. 35th 300 . 304. .250 3""- a — PH .200. 30“ /50 w ’50" /OO _ IOOL :0 . ‘0 ~ 0 o A, A; 8, 6‘ 6' A, A‘ as 8‘ Fig. 5c Rubicon sand rig. 5d Ogemaw sandy loam KJ. Inn. 300 P 300 P 4830 H—T 250 . _ zoo. zoo. ’50 fi- ‘1 [:0 L we . MO . 5p . .s'a . a ”Annama- mace Base-exchange capacity of the soil organic matter at various depths expressed in milliequivalents per 100 grams of organic matter. Fig. 5e Kalkaska loamy sand MOE. 300 2:0 2 w ‘_e lee [—- l0 5'0 0 Al A‘ 3, ‘J7- fig. 51’ ‘mmet loamy sand 11.3. .200. 4:0. /aafi. ‘:* W] A, A; as a; C’ 7 87. greater than for any of the other soil types studied. This .possibly is due to a difference in the chemical constitution of the organic matter. Apparently the organic fraction in the Selkirk and Isabella soils has undergone hydrolysis ca» pacity tremendously. The organic matter in the other soil types has undergone a slightly different degradation, due possibly to the influence of such factors as pH, increased drainage and biological activities; consequently, its base- exchange capacity is somewhat lower. The sriter is aware that the base-exchange capacity of the organic fraction in horizon ‘2» figure 5a and horizon Bl, figure 5b is extremely high. then a soil sample contains less than one per cent organic matter, as some samples did, the results had to be multiplied by a factor that was larger than 100. Therefore, when such a large factor is used, the slightest error in the determination will result in a large final error. The graphs in figures 6a and 6 b shoe that there is a general decrease in exchangeable caloium.and magnesium.as us go deeper in the profile. ‘Hoeever, it can be seen in figures as and 6 b that there is more exchangeable calcium and mag- nesium in the 31 than ‘2 horizon in the Kslkaska loamy sand. In the horizons that contained carbonates, exchangeable calcimn and magnesium were not determined. Table 8 shoes the base-exchange capacity of a soil sith the ammonium.acetate adjusted to a.pH of 7.0 as compared to the attraction made eith the ammonium acetate adjusted to the pa of the soil. Hilliequivalents of exchangeable magnesium per 100 grams of oven-dry soil at various depths. 1'13. 66 Rubicon sand M . . Kalkasha ’ —‘— loamy sand unmet lo 3 4 “ — --'--- send any 89. Milliequivalents of exchangeable calcium per 100 grams of oven-dry soil at various depths. [11.3. L Big. 6b l I la - 9 Rubicon send a Kalkaska ’ §‘§ loam sand must loam ““““ sand 7 - 30. T3310 80 Base-exchange Capacity in M.E. per 100 grams of oven-dry Soil Soil Type l. Isabella Loam z. Selkirk :g% of soil I 7,8I 7,6; 7,7“ I 8,2 I 8,1 Loam. : c a us a o, . : Hrof the soil ° 4 ‘ 3 4’14 5 : 7 l ’ 0 9 : we a “8 9 . . . . . :3E 02 7,0 I;!,3I15,4;14,6 ‘ 6,§ ' 6,8 :5. Rubicon :pg of soil 2 7.6; 7.2: 7.0 I 6,5 I 6.2 Sand =NH4A0 adjusted to: 3 ; z : :33 of the soil 1 7,9. 2,0‘ 3,0 t 1,1 s 0,6 ‘NH4Ac adausted to : ; g ; :pHo 3 7.2. 5.0. 5,0 . 1.1,; 0.6 4. Ogemas : H of 8011 I 7.8: 8.0: 6.8 3 I 7.8 Sandy :EHZAc adflusted to: : : : : Loam :23 Hot the soil . 5,3. 2.6. 3.9 . . 3.6 3W0 adgusted 120;; g g ; ,gnfi,of 7.0 ~ 4.4- 3,0. 3a8 . - dis 5. Khfllkas- : Of .011 ; 7,4: 7.7: 7.: g 8.0 7.8 RC. LOW : L0 a 118 CC toi ; g : Sand 2 of the soil 4 8. 8 7- 5.0 - z 6 0 7 O. .0. I. Q. .0. D. 0. EE 0: 7,0 2 5,8: LE. ‘Q‘ g 3.0 006 6. Bumet : H of soil - 7 - . s : 7 Loamy : J : : z : Sand :ng of the soil 310,§; ;,6; 2,5 g ;,g ; 0,1 :Nflade adgueted to} : : : : :33 o; 7. :11,;: ;.5: 3.4 : 0.9 : 0.5 31. 0f the 29 soils samples examined, twenty-one had a pH value greater than 7.0, six had a value below 7.0 and 8 were neutral. When the base-exchange capacity of the twentyvone basic soils were studied, it was found that when ammonium.ace- tate was adjusted to the same pH as that of the soil, in fif- teen of the cases the base-exchange capacity was greater than the value obtained with the ammonium.acetate at a pH of 7.0. In four cases when the ammonium acetate was adjusted to the higher value, lower results were obtained, and in 3 cases the results were the same. or the six acid horizons examined, three gave a lower base-exchange capacity when the ammonium acetate was adjusted to the pH of the soil as compared with the ammonium acetate adjusted to a pH of 7.0. The soils gave a higher result and one the same when ammonium acetate was adjusted to the pH of the soil. It can be seen from the data in table 2 that when the ammonium acetate was adjusted to the same pH as that of the soil, higher results were usually obtained, especially with the alkaline soils. This difference depended.msinly upon the pH and the approximate base-exchange capacity of the soil. When the pH of the soil was high, usually greater differences were found. There were not enough acid soils studied to draw any con- clusions as to the effect of the base-exchange capacity when the ammonium acetate was adjusted to a.pH of 7.0 as compared with the ammonium acetate to the same pH as that of the soil. in attempt (Fig. 7), was made to determine whether the base-exchange capacity of the organic matter would show a 32. .30pr ougmho a.“ .Hda Q.\ m. m K v k. t. m. N . . . . _ . \ .. . a e o o O O 0 O. o u e e l \ . s - .N . . m. - at oomé u soupeaennoo , _ no 233.380 - M. houses 3598 peso hem oflfloagufi hounds GHfiflWHO .HO Pfloo Hem edge on» no 3333 emosooneaoeeo no maneonumwamprfl h .mwh 55. direct correlation with the per cent of organic matter in the soil. It was found that there is a general increase of base- exchange capacity of the organic matter as the per cent of organic matter increases. The coefficient of correlation was found to be 0.899 which shows that there is a fairly close correlation between per cent organic matter and milliequiva- lents base-exchange capacity of the soil organic matter. SUMMARY 1. Base-exchange studies were made of six soil pro. files found in Michigan. 8. anide variation in base-exchange capacity of the different soil profiles was noted. Similarly, a wide varia- tion in base-exchange capacity at different depths of the same profile was noted. 3. Heavy textured soils have a far greater base-exchange capacity than light textured soils. 4. It was found that the organic matter contributed over one-half of the base-exchange capacity in the A1 horizon of all the soils studied. Except for the zone of accumulation, it was found that with increasing depth the percentage of the organic matter becomes less and the percentage of the base- exchange capacity of the soil due to the organic matter also decreases. 5. The base-exchange capacity of the soil organic matter in various profiles within the different horizons of the same , profile expressed in millicquivalents per 100 grams, was found to vary widely. 54. 6. Exchangeable calcium and magnesium tend to decrease with increasing depths in the profile. 7. Comparing the base-exchange capacity, obtained with alkaline soils, when the ammonium acetate was adjusted to a pH of I7.0 with that obtained when it was adjusted to the pH of the soil, it was found that a higher base-exchange capacity was usually obtained in the latter case. 8. When per cent organic matter was plotted against milliequivalents of base-exchange capacity due to the organ- ic matter in 100 grams of soil, the coefficient of correla- tion was found to be 0.809. 1. 8. 3. 4. 5. 6. 7. 8. 9. 10. 11. 13. 55. BIBLIOGRAPHY Alexander, L.T. and H. G. Byers, A critical laboratory 1988 review of methods of determining organic matter and carbonates in soils. U.8.D.d. Tech. Bul. 317e Bower L.D., The effect of organic matter upon several 1950 physical properties of the soil. Jour. um. Soc. Agron. 88:703-708. Gedroiz, K. K., The soil absorbing complex and the ab~ 1939 sorbed cations of the soil as a basis for a genetic soil classification. Nosov Agr. Exp. Bul. 38 Leningrad, 1935; Kelloidchem. Beih. 89:149. Der adsorbierende Bodenkomplex. Reprint I!!! from Kolloid - Chem. Beihefte by Theodor Stienkopft, Dresden, and Leipzig. Contributions to our knowledge of the absorp- ' I515 tion capacity of soils. Zuhr. 093th. Agron (Russian) 19:269. 8. A» Waksman's.mimeograph- ed English Translation of the Gedroiz Papers Ye a: 8, 90 Kerr .W., The nature of‘base-exchan~ and soil acidity. 16cc dour. Am. Soc. Agron. 20: 9-335. Mececrge, W.T., organic compounds associated with base- 1931 exchan reactions in soils. University of Aria. ch. Bul. 31. Mattson, Santa, The relation between the electrokinetic 1985 behavior and the base-exchange capacity of zgél colloids. Jour. Am. Soc. Agron. 8:458- 0 Mill”. H. c.’ I. B. suith, and PO 3. 31’9“. m. b880- 1956 exchange capacity of decomposing organic matter. Jour. in. Sec. Agron. 28:758-766. Mitchell, J., The origin, nature and.importance of soil 1953 organic constituents having base-exchange prop- erties. dour. Am. Soc. Agron. 84:856-875. Mitchell, R.L., Baseéexchange equilibria in soil profiles. 193? Joure Agr: 801. 873557-567. Olson. L.C., and R. H. Bray. The determination of the or- 1958 ganic base-exchange capacity of soils. Soil ‘m501e 45:485-496e 13. 14. 15. 16. 36. Russel, J.c., A.method for the continuous automatic ex- 1955 traction of soils. Soil Sci. oozeet-ecc. Turner, P.E., An anlysis of factors contributing to the 1988 determination of saturation capacity in some tropical soil types. Jour. Agr. sci. 88:73- Weksman, 8.3., 'nunus', williams a Wilkins 00., Balti- 1986 more, pp. 513. Fly J.T., 9n the power of soils to absorb manure. 1858 Jour. Royal Agr. Soc. 13:125-148. APPENDIX Analysis of the soil profile expressed on a basis of 100 grams of water-free soil. Wm M :1 ‘fi ”1 "8 ‘L. Per cent moisture 6 51 s 50 i 3.9 7.0 7.7 7.8 s.s Per cent or anic matter 5.58 0.76 1.16 0.35 0.51 HIIie quivafen ts __ base-excha e ca acit 11.6 11.5 80 11.5 9.4 Mat-arr W or is matter destro ed 5.7 6.7 15.9 9.5 7.6 Eco oexchange capacity of f , _' or anic matter 7.9 4.8 6.1 8.0 1.8 fircentage of base-exchange capacity due to organic matter “e1 4167 30.5 lye‘ 1’e_3__ reentege of base-exchange capacity due to inorganic utter 31s, 58s: 6.e5 82.6 80.. MIII. qu IVQICn 5‘ O! CIQhQHB.’ 81916 Ca 13.: 3.8 -- -- -- - equ vaen s 0 exchange- able 3 0.8 1e 6 -" -0 In. Percentage Of CICOQC --- -- 8.00 31.49 33.05 II Analysis of the soil profile expressed on a basis of 100 grams of water-free soil. LONE Horizon 1; £3 81 Ba a Per cent moisture 8.85 4.80 7.54 1.79 5.09 _2§#_ 7.8 7.6 1.7» 8.8 8.1 Per cent or anic matter 5.80 5.11__0.87 0.65 0.49 "mm. qu Iv'ife'h' 't s base-exchan e ca acit 15.5 15.4. 14.6 6.8 6.8 Easeiixcfiafige capacity 6115* organic matter destroys 4.8 5.1 10.5 5.5 5.7 Base-exchange capacity 0 or anic matter 8.5 8.5 4.5 1.5 1.1 Pircentage of base-exchange capacity due to organic matter 65.9 61.9 89.4 88.1 16.8 Percentage of‘base-exchange capacity due to inorganic matter 56.1 58.1 70.6 77.9. 85.8 EIIIIe"q_uIv'a"Ie"n'ts of exchange- * . able Ca 13.} 13,4 -- -- .- Milliequivalentsof—exchange. M 40° 3;” -Q -- .. if Percentage of 0300§ -- -- 7.46 51.18 53.45 III Analysis or the soil profile expressed on a basis or 100 grams of waterctree coil. RUBICQN SAND __§orizcn £1 ‘8 31 -Bg. c For cent moisture . , 7 0 0 ,7 fl ’ J c 7 7 c 5 Per cent or anic.mattcr §.§g 1,3; 9.21 0.4! 9.18 mIquuIvEIenta base-exchange c acit 7 . _ "Eace~exchangc capacity”iiii ‘ ' ' 'i or anic matter destroyed 1.9 ;,§ 9.2 9.: 9.; Ease-exchange capacity Etc ' to or anic matter $.§ 1.5 ;.§ 9.5 9.; Pircenfage' of base-exchange capacity’duc to organic matter 8 f 3 6 For rcentase chine-exchange " ‘ capacity due to inorganic Wfiur WM equ r an s 0 exchange- able Ca g.g a.§ 1" glg 9'5 '1ieqaivaIenta cIFeXchangeu ‘ able £3 1,! 9.5 , Qn§ 9.5 9.] Analysis or the soil profile expressed on a basis of 100 grams or rater-free soil. new __ Jogger: ‘ f ’ H 8 Cr Per cent moisture a.“ , 3 IE 3 lg; ”g .E _ 7 . e c 7 Per cent orfanic majje; * 7 0 45 8'! 0 55 cqu va ante base-exchange capaci? 4.4 8.9 5.8 4.5 Taco-exchange capac y s __qrganic matter deatrgy ed 1,; hg 9.6 h! Base-exchange capaci y o ' organic matter 5.5 1.0 5.; 0.8. rccn age 0 base-cxchange ' 'capacity due to organic matter 75.0 gmg 84.! 12.9 ‘Fercentage of baeewechfange capacity due to inorganic matter - 85.0 59.2 15.8 81.9 E, IIIquuIIa'Iem'tn 's of ex"c'fianee- ‘ , able Ca 93g 3.; §.§ -- Milliequivalents oFexcEange- Percentage of 0300; -- -. -- m Analysis or the soil profile eXpreeeed on a basis of 100 grams of water-free soil. mesa Lem 5gp ‘— Horircn 1 ‘1 ‘3 31 83 c‘ Per cent moisture 8.55 g_g§ 1.5g g,§g 3.9; JR 7.0 7.7 IS'.5 8.0 7.8 Per cent or anic matter , c7 5 ’ 7 fiIIIqunIvaIents ‘ base-exchange capacit 4 0 8.8 4.4 8.0 0.8 Base-exchange capacity 7135 organic matter destroyed 1.0 0.9 31.53 8.5 0.4_ Tine-exchange capaci y no ' to organic matter 5 l 5 5 7 "Fircentage ofAbase-exchsnse capacity due to organic matter 75.0 59.; 68.7 85.0 58.1, Pareentage of‘base-excfiange capacity due to inorganic mat“: 853° ‘6.’ 87.3 L530 67:? fiIIIqunIvEIents of exchange- able Ca 6.8 .3.0 4.5 #8.? 9.8 MIIIquuIvHents of exchange- abl. E3 139 0" 018 +0.6 01L P01360358” Of 6‘003 _. -- en- es. es. __£ analysis or the soil profile expressed on a basis or 100 grams of watervtree coil. EMMET LOAN! SAND 0 £1 33 6 Per cent moisture a 87 5 4 15 05 _pfi' 7 6 6 5 c 5 Per cent or anic matter 5.57 9.55 1.65 9.48 9.14 Milliequivafcnis base-exchange capacitz_ ;;.; ;.5 5.5 0.2 9.5 "fiaee-excfiangc capacity sit5* organic matter destroyed ;.§ g.§ o.§ g.§ 9.5 Ease-exchange capacity due ‘_39 organic matter 6 0 7 5 Percentage ofbaee-exchange capacity due to organic matter 88.5 46.1 76.5 45.5 39.9 'Fbrcentige airbase-exchange capacity due to inorganic matter 5 3 3 5 fiIIIqunIvEIents of exchange- able Ca ;o.3 9.2 9.5 g.§ 9.1 MIIIqunIvEIents of exchange- able ya a 5 o c Percentage of 0.005 "if .1 w“? " vza, T631 .4 T257 127451 Tedrow