H! M + \ lHlHlHl 1 | HI m» l » A DDMPARATWE STUDY OF EMPPED AND VIRBIN SOILS THESIS FDR THE mm m mom BF mesarm ' CLARENCE DORMAN I932 THESIS an" A COMPARATIVE STUDY OF CROPPED AND VIRGIN SOILS By Clarence D322. A THESIS PRESENTED TO THE FACUIII‘Y OF MICHIGAN STATE COILEGE 0F AGRICUIEURE AND APPLIED SCIENCE IN PARIIAL WILHEM‘ OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHIIOSOPHY East Lansing 1932 THESIS ACKNOWLEDGMENT The writer wishes to express his sincere gratitude to Dr. C. E. Millar for helpful advice and criticism éuring the progress of the work and in the preparation of the mann- script. 95502 IITEODUCTIOH Several workers have reported studies in which partial analyses were made of cropped and the corresponding virgin soils. host of these included the determination of one or more of the following: pH, phosphorus, calcium, magnesium, composition of soil solution, and exchangeable calcium. .A number of workers have reported results of base exchang studies on soils that have been cropped for different periods of time. In general, these studies deal with soils which have received constant fertilizer treatment for a great many years. In some cases, however, unfertilized soils have been included. In so far as the writer is aware, little information is available regarding the exchangeable bases and composition of cropped soils and the corresponding adjacent virgin soils. A study of exchangeable bases tOgether with a chemical analysis of cropped and virgin soil should throw some light on the changes which a soil has undergone by continuous cropping. The relation between the change in the composition of the absorption complex in the soil, due to cropping, and the chemical composition of the soil has not been established. The change in the relative proportion of the bases in the soil with the change in the total of the bases is uninvestigated. The removal of bases from the absorption complex by crOpping must be fol- lowed by a continuous process of recovery or we would have after a relatively short period of cropping a complex with practically all bases removed. The proportion of the different bases in the soil that is exchangeable should give some indication Of the capacity of the soil to furnish plant food. It is the purpose of this paper to throw some light on these questions and to set forth any relationships found to exist between the amounts of various plant food elements in cropped and the corresponding adjacent virgin soil and the exchangeable bases. LITERAT’EE CITED The literature of the subject, base exchange, has been extensively reviewed in a number of recent publications, therefore an exhaustive review is unnecessary in this thesis. Hany papers have been called to the attention of the writer, but only those dealing more or less with the subject of the paper will be cited. Miller (15) determined the rate of formation of soluble material in several virgin and the corresponding depleted soils by means of the freezing point method. On the whole, the data showed that the surface soils of the virgin samples possessed the power of giving up soluble material at a greater rate than the corresponding cropped.samples. No appreciable difference in the rate of solubility of the subsoils from the depleted and virgin soils was observed. The amounts of various materials going into solution from depleted and virgin soils maintained for three weeks at room temperature with a moisture content somewhat above saturation, were determined. With one exception, the cropped soils yielded more sulphates while the virgin soils gave the greater amounts of iron, aluminum, calcium, and magnesium. Martin (12), in studying soils in iron containers, crOpped one set of soils to barley continually for twelve years. Another set was crepped to barley one year, fallowed ten years and again cropped to barley. Exp changeable bases were determined on these soils and also on samples of the original soils. Ho significant differences were noted in the exchange- able calcium, magnesium, and sodium of the continually cropped and fal- lowed soils; but exchangeable potassium showed a marked decrease as a result of cropping. This experiment was conducted under conditions which -3- precluded the loss of any of the four bases from the soil except by crop removal. Fraps (5) found that the quantities of water-soluble potassium, the potassium soluble in 12 per cent EDl,and the replaceable potassium in certain soils were all related to the potassium removed by crops in pot experiments and to the "active" potassium of the soils. The amounts of water-soluble potassium lost from soils by cropping and the replaceable potassium lost by crOpping were related to the amount of potassium taken up by the crop grown on the soils and to the "active" potash lost by cropping. The amount of potash taken up by two crops usually averaged five or six times the quantity of water-soluble potassium and about one-half the replaceable potassium in the soils. The amount of potassium removed by the crops from the soils was usually eight to sixteen times more than the water-soluble potassium and about twice the replaceable potassium lost in cropping. Ogg and Dow (17) found decidedly more exchangeable calcium, a ' higher pH value and lower "lime requirement" in cultivated soils as a group than in "Woodland", "Hill or Heath" soils, or soils left "long unploughed". In addition to this general comparison, they studied more in detail a number of uncultivated soils and the adjoining culti- vated soils. Their data showed that the uncultivated land had a much lower pH value than the adjoining cultivated land. The exchangeable calcium was determined in the surface nine inches of the cultivated and adjoining uncultivated soil in one case, and the results showed that a cultivated soil had almost double the quantity of exchangeable calcium than an adjoining uncultivated soil. -h- Gedroiz (6) made a study of the relation between exchangeable cations of soils and plant growth. He found that after the practically complete replacement from the soil of exchangeable calcium, the plants required for their development in this soil the addition of calcium fertilization, without which they did not grow at all. They were evidently unable to utilize the unexchangeable calcium of the soil. After the practically complete replacement from the soil of magnesium and potassium, plants were able to develop and give a more or less normal yield even without the introduction of magnesium and potassium fertilizers, showing that the plants were able to utilize the unexchange- able magnesium and potassium of the soil. Glinka (7) showed that the pH value of uncultivated podsol soils in the neighborhood of Leningrad was M.5, while arable soils of the same class had a pH of 5.5 to 6.2. Ames and Schollenberger (1) determined the total calcium and magnesium and the calcium and magnesium soluble in fifth normal nitric acid in some cropped and virgin soils of the same type. They found, in most instances, that the proportion of total calcium and magnesium, especially calcium, soluble in fifth normal nitric acid was greater in the surface (0 - 7 inches) virgin soil than in the same depth of cultivated soil. However, when the data for the 7 - 15 inch depth of these soils were compared, the reverse of this observation was found in many cases. In the total analyses for calcium and magnesium.no consistent differences were shown. Schollenberger and Dreibilbis (21) working with the soils of the fertility plats of the 5-year rotation at Wooster studied the effect of cultivation with and without fertilizer and lime treatments upon the -5- exhhangeable bases of the soil. They found that the amount of exchange- able manganese, calcium, magnesium, potassium, and sodium had decreased, whereas the exchangeable hydrogen had increased, as a result of 31 years of cropping without fertilizer or lime. There had been also a net decrease in the total bases and the exchange capacity. Page and Williams (18) studied the content of exchangeable bases in the soil of certain plats on Broadbalk Field and the Grass Plats of Rothamstead. In the case of the Broadbalk Field a complication is introduced due to the former practice of Chalking the land at very heavy rates. This work showed that the relative proportions of the different bases varied consistently with the manuring and that there was probably a gradual conversion of exchangeable potassium to a non-exchangeable form, or vice versa, depending on whether or not potassium fertilizers were used. Crowther and Basu (h) studied the influence of fertilizers and lime on the replaceable bases in a light-textured, acid soil after 50 years of continual cropping with barley and Wheat. The replaceable calcium had decreased under all treatments. .A mineral treatment increased the replaceable magnesium and potassium, but it was insufficient to balance the loss of calcium. Wilson (26), on making a study of exchangeable calcium and potassium in soils as affected by cropping and fertilization, observed that the exchangeable potassium and, with one exception, the exchangeable calcium in the untreated soils during the 15 years of the experiment, was reduced. These soils were held in cylinders but were subject to leaching. Miramanoff (16) reported that the process of the formation of fine soil particles was speeded.up under prolonged cropping to alfalfa as f -0.- compared to soil in the virgin state. The sum of replaceable cations more often increased than decreased in the cropped soils and was greatest in the surface layer but gradually decreased with soil depth. Exchange— able potassium increased while magnesium decreased in the upper layers of the soils, but increased in the lower layers and sodium decreased in the lower layers. Metzger (1%) studied the effect of moisture content and crOpping on exchangeable calcium and magnesium in rice soils. The soils investi- gated had been under control for 16 years and had not received any fertilizer treatment. He found an increase in the exchangeable calcium and magnesium in the surface soils. Some of this increase is probably due to the fact that the irrigation water contained calcium and magnesium. Hissink (10) states that the non—exchangeable potassium of soils changes to exchangeable potassrrn. -7_ LESORIPTIOE OF SOILS The soils investigated are classified as Plainfield loamy sand, Coloma loamy sand, Hillsdale sandy loan, “College Farm" (Hillsdale sandy loam), Miami loam, Nappanee silt loam, and Ontonagon clay. In virgin areas of Plainfield loamy sand an extremely thin layer of litter and "mold" or F layer is present on the surface. This is underlain by a fine, granular, light brown loamy sand ranging in thick- ness from one to four inches, and beneath this layer is a dull yellowish colored loamy sand from ten to fifteen inches thick. This latter material grades to a paler yellow or cream colored incoherent sand, which, at a depth varying from thirty-six to forty inches, grades to the substratum of sand or sand and gravel. Plainfield loamy sand is a level outwash soil with rapid drainage. The mixture formed by plowing this soil to a depth of six or seven inches is a light grayish-brown loamy sand. Virgin Coloma sand has an extremely thin layer of litter and "mold" or F layer on the surface; underlain by a layer of mixed sand and organic matter from one to three inches thick. Below this is a layer of dull- grayish colored sand from one to four inches thick, underlying which is a dull or brownish-yellow loamy sand layer, varying from ten to twenty inches in thickness, grading to a paler yellow or cream colored incoherent sand layer. Unaltered parent material of sandy drift occurs in this soil at a depth ranging from three to five feet. The drainage of Coloma sand is rapid. The color of the cultivated soil is a light shade of brown. The surface layer of virgin Xiami loam consists of a thin layer of litter and "mold" or F layer. Below this layer there are three to four inches of loamy soil material having a coarse, granular structure, with a.moderately high degree of humification. Three to eight inches of ashy .3. light gray soil, high in silt, underlies the "humified" layer. The ashy gray layer grades to a.yellowish brown, rusty mottled, coarsely granular, more colloidal material continuing in some cases to a depth of forty inches. The parent soil material is a massive, comparatively impervious glacial till. The topography of Miami loam varies from nearly level to rolling or even moderately hilly. The color of the dry cultivated soil is a light shade of brown. In the virgin state Hillsdale sandy loam has a very thin layer of litter and "mold” or F layer, and underlying this are three to six inches of grayish brown light loam or sandy loam soil. Below this layer is a pale yellowish friable sandy loam soil five to fifteen inches thick exhibiting evidence of leaching. This grades to a.yellow and yellowishe brown (faintly reddish brown in places, especially when wet) material from eighteen to twenty-four inches thick, containing considerable quantities of clay but yet sandy, friable, and of a finely granular structure. The substratum.of sandy clay material may be moderately stony. The topography is rolling to hilly and the drainage is good. The color of the dry cultivated soil is a light shade of brown. The virgin Nappanee silt 10am consists of a thin surface layer of litter and "mold" or F layer, then three to five inches of loamy humus soil which is underlain by three to six inches of a grayish colored, loose.soil material higher in silt content. Below this is a gray or drab colored,compact, plastic, impervious clay containing yellowishrbrown mottling or stains, which are most marked at the top of the layer. At a depth of fifteen to twenty-four inches, this clay rests upon a bluish— gray, gritty or stony, but compact and relatively impervious clay, ex- tending to depths of several feet. host of the type is characterized by -9... comparatively gentle or smooth slopes and the natural drainage is only fair. The surface soil of cultivated fields varies from lifht brown to ash colored. The virgin Ontonagon clay consists of a surface layer of litter and "mold" or F layer, two to three inches thick, which grades into a layer of dark gray humus soil about two inches in thickness and ranging in texture from a silt loam to a silty cl y loam. Below this is a light gray or faded red colored, friable silt loan to silty clay loam varying from five to six inches in thickness. Below this is a reddish, fine grained, impervious clay, exhibiting a faint brownish coloration or mot- tled condition at the top, which extends to a depth of twenty-four to thirty inches. This soil has a light red colored clay substratum. Some of the Oatonagon clay is nearly level or flat, but much of it is gently rolling. The movement of water in this soil is very slow and, therefore, drainage is poor. Under cultivation the surface soil is a light brown or reddish colored silty clay loam. -10- COLLECTIOH OF 8A3? ”"1 The samples represent the surface stratun of six or more inches depending upon the depth to which the soil had been plowed. Careful attention in the selection of fields for sampling was necessary in order to select cultivated fields that apparently were free from erosion and had received no lime or commercial fertilizer. This task was made more difficult as it was desired to take the virgin soil sample from a tract of woodland only a short distance from the site of the first sample. Ho soil samples taken from fence rows are included in this in- vestigation as these soils represent a more or less prairie condition. In taking these samples the slittef of the virgin soils was not included, as in clearing land for cultivation this material is largely destroyed. Two samples were taken from each soil type. One from a field which had been under cultivation for a considerable n‘nber of years and had decreased more or less in productivity; and the other from a virgin wood- land soil a short distance from the site of the first sample. The first sample is designated as crepped soil, while the latter is referred to as the virgin soil. The samples were taken to the laboratory, air dried, and passed through a 2 mm. mesh sieve to remove pebbles and the coarser organic material. They were then thoroughly mixed and stored in suitable containers until utilized in the experiments. The methods used in these determinations may be divided into two groups: first, methods dealing with chemical analysis of the soil, and second those concerned with some phase of base exchange. In this paper, however, no detailed procedures will be given. In the total analysis of the soil, the methods as outlined by the Association of Official Agricultural Chemists (2) were used for determining total nitrogen and phosphorus. Their methods were also used for making the sodium carbonate fusion and the determination of silica, iron, aluminum, and calciumi Magnesium was determined by Handy's (8) well known method. Sodium and potassium were determined by.the procedure described by Scott (23). Hydrogen ion concentration was measured by the use of the quinhydrone electrode as suggested by Bauer (3). Schollenberger (20) points out the advantageous features of a neutral solution of ammonium acetate for the estimation of all exchange- able cations in the soil. The methods and aoparatus described by Schollenberger and Driebilbis (22) were used in the extraction and determination of the exchangeable cations with the exception of exchange- able ammonium. The method of HcLean and Robinson (13) was employed to estimate exchangeable ammonium. The procedure of Kelly and Brown (11) slightly modified by Schollenberger and Driebilbis (22) was followed in the determination of absorbed ammonium. The available or easily replaced, exchangeable calcium was estimated by the procedure of Parker and Pate (19). In determining readily available phosphorus the method outlined by Truog (25) was employed. -12- EEK CAL AI“LYSIS OF TIE SOIL It has been stated th:t chemical composition is closely related to the wearing qualities of the soil and its ability to persist in production under cultivation. One of the objects of this sturv was to learn the effect of cropping on the chemiCal composition of soils. The analyses are shown in Table l. The values are expressed in per cent. With the exception of nitrogen content, a comparison of analyses of cultivated and virgin samples of the seven soil types, as a group, show no significant differences. However, when the data are studied in regard to any given soil type, in many instances, wide differences are noted. These differences within any given type are usually reversed in one of the other types. Of the soil types studied, there is no significant difference in the silica content of cultivated and virgin soil. In the iron content a difference greater than the experimental error is found in three soil types. In the college farm (Hillsdale sandy loam) and Miami loam the virgin soil contains more iron than the cultivated. This order is reversed in the case of happenee silt loam. The Happanee silt loam.shows a higher aluminum content in the cultivated state than in the virgin condition. The amount of aluminum in cultivated and virgin Coloma loamy sand is the s me, while the other types have slightly more in the virgin soil. Ho consistent differences were found in the calcium and magnesium content of the virgin and cultivated soil samples of the soil types studied. This result is in agreement with the findinrs of Amos and Schollenberger (1) in their determination of total calcium and magnesium. The calcium and magnesium content of cultivated miami loam is considerably -13- greater than that of virgin hiaai ion“. .A difference in the same direction is found in the Ontonagon clay and Xappanee silt loam. The percentage of M50 is greater than the percentage of CaO in cultivated Ontonagon clay and in both soils of Nappanee silt loan. 'However, when these percentages are calculated to per cent calcium and magnesium, the per cent of magnesium is greater only in the cultivated happenee soil. .As in the case of calcium and magnesium there is no consistent difference in the potassium and sodium content of the virgin and culti- vated soil. When each type is considered separately we_find some marked differences. Four of the soils contain more potassium in the virgin samples and three contain more in the cultivated. Some of these differences are great enough to be significant. Since all the error in determining sodium and potassium falls on the sodium determination, in order to be of value appreciable difference in the sodium content of the samples is necessary. The cultivated soil of the College Farm, the virgin soil of Miami loam, and the virgin Plainfield soil contained, noticeably, more sodium than the corresponding virgin or cultivated soils, respectively, of these types. When a comparison is made of the nitrogen contents on the percentage basis it is found that with one exception there has been a decrease in the nitrogen content due to cropping. This is in agreement with the findings of a number of investigators working with a large variety of soils, Some of these results have been reviewed by Swanson and Latshaw (2h). With the exception of one type, the cultivated soil contains from 100 to MHO pounds less nitrogen per acre than the virgin soil. his means a loss of 5 to 20 per cent of the original amount of nitrogen. The loss indicated would no doubt have been greater had the surface litter or "mold" been included in the samples from the virgin soils. The cultivated Hiami loam -ll+- contains l6u0 pounds more nitrogen per acre than the virgin soil. This great increase is difficult to explain, but is probably due in part to the method of sampling, the system of farming, and to a high nitrogen fixation by micro-organisms. In comparing the amount of phosphorus found in these soils there is no difference consistent throughout the types. However, if the soils are divided into the lighter and heavier soils good agreement is found. The phosphorus content of the virgin soil is used as a basis of come parison. In the four lighter soils the virgin soil contains from O to 600 pounds more phosphoric acid per acre than the cultivated soils. This means a loss of O to 20 per cent of the original amount of phosphoric acid. In the three heavier soils the cropped soil contains from IMO to 1220 pounds more phosphoric acid than the virgin soils. This means a gain of 7.5 to 6% per cent of the original amount of phosphoric acid. The gain of 6“ per cent was made by the Miami loam which made such an increase in nitrogen content. This increase in the heavier soils is probably due to the plant growth being greater and the bringing up of more phosphorus from the lower horizons. -15- xfi’VrL‘Tr|*1A"3-JE BLSTS The analytical data for the base exchange studies are presented in Table 2, together with the milliequivalents of ammonium ion absorbed and the pH values. In practically all cases ittle difference is found in exchangeable hydrOgen between crOpned and virgin soils of the scme soil type. The pH values of these soils are quite noticeable due to the fact thpt there is such a very close agreement betv.een the crooped and vir :;in samples. These data show that th re has been no change in pH ‘ue to cropding, and no correlation between exchangeable hydrOgen and p? is shown; however, when texture is considered along with pH a correlation is shown. This is noted particularly in Hi llsdale sandy 109;--pH 5.MO, Happanee silt loam-—pH 5.Hl, and Cntona con clay pH 5.hl. The exc.angeable hydrogen in these soils is 0.72, 2.89, and 5.03 milliequivalents, respectively. The content of exchangeable aluminum and manganese in the soils studied was relatively low with no consistent increase or decrease due to cropoing. The amount of exchange able aluminum and In anganes e had a positive correlation with the exchangeable hydrocen. This is in agree- ent with the findings of many workers. The exchangeable bases ca slcium, magnesium, sodium, and potassium vary widely when each type is considered separately. However, the mean values for cropped and vira in soils seem to indicate thzt the bases have remained fairly constant. The greatest variations in calcium are found in the lighter soils. Two soils, College Farm and Coloma loamy sand, indicate that there has been a considerable decrease in exchange- able calcium, wh ile three soils indicate an increase. -16- As judged by the mean values for the group, magnesium.shows a slight increase in the crOpped soils. However, two soils show a very marked decrease in magnesium. These two soils, Coloma loar' sand and College Farm, also show a marked decrease in exchangeable calcium. Sodium does not seem to undergo any uniform or significant change;the average content for all tne soil types is nearly constant. There are about an equal number of increases and decreases in the cropped soils, using the virgin soils as standards, with a slight increase indicated. Potassium does not seem to undergo any large change. Outside of the loss of more than 50 per cent of the exchanseable potassium in the cropped College Farm soil there was no other large difference found. Four soils indicate a decrease and two an increase in exchangeable potassium. From the small quantity of exchangeable potassium found in these soils, both cropped and virgin, it is evident that crops on these soils obtain their potassium from some source in addition to the exchangef able potassium in the surface soil, undoubtedly in part from the exchange— able potassium in the subsoil and probably potassium that is in a non- exchangeable form. The total bases found and the sa'uration capacity show good agree- ment except in the case of Coloma loamy sand where the total bases are considerably greater than the absorption capacity. This indicates the presence of free carbonates in this soil. As in the cases of the individual ,bases there is no consistent difference throughout the types. Five soils indicate an increase in base caoacity and total bases in the cropped soils, while two indicate a decrease. The increase of the absorption capacity in the cropped soil, using the virgin soil as a standard of comparison, varies from 3.5 per cent in the Kappanee silt loam to M3 per cent in.hiami loan. The decreases in absorption capacity are shewn by Coloma loamy sand -17- and Hillsdale sandy loan. The hich per cent increase shown by 11221 hcnfe lomn is undoubtedly in part due to an increase in the org2.ic ezc complex, as the cropped soil shows a marked increase in orgsnic matter. -18... IOIAL Bless A713 sandman mess The relationship that exists between the total bases in the soil and the amount of exchangeable bases should be of interest. The relative proportions of the different bases that are in the exchangeable form should give some indication of the capacity of the soil to furnish these ases. The per cent of the total of each base tth is exchangeable should give a good indication of the changes thpt have occurred in the soils studied and reported in this paper. In Table 3 the per cent bases and exchangeable bases and per cent of total bases exchangeable are given. These data are on the elements in all cases; thkt is, per cent calcium, and milliequivalents, exchangeable calcium calculated to per cent exchange- able calcium. The mean values show the per cent of the total calcium that is exchange- able to be almost constant. Four soils show a greater per cent of the total calcium.in an exchangeable form in the crOpped soils, while three cropped soils show a smaller per cent to be exchangeable than in the cor- responding virgin soils. mnen the different types are considered as a unit very little correlation is indicated between the total calcium and exchange- able calcium. The per cent of calcium that is in the exchangeable form increases as the soil becomes heavier, with the amount exchangeable ranging from 3.36 per cent in virgin Plainfield loamy sand to 35.55 per cent in cultivated happanee silt loam. The per cent of the total magnesium exchangeable varies considerably within soil types. Some crOpped soils show a.marked decrease while others show a large increase over the corresponding virgin soils. In most cases, these changes in any given type are in the same direction as the changes -19- in the per cent total calcium.excha.geable. The average for the cropped soils is n.51 per cent, and the average for the virgin soils is “.61 per cent; thus the mean values indicate that the per cent of total magnesium exchangeable is about constant. The relative proportion of magnesium exchangeable increases as the soils become heavier. The data indicate no correlation between the total potassium and the amount exchangeable. The per cent of the total exchangeable potassium.increases as the soil becomes heavier. The College Farm soil shows the greatest decrease, more than 50 per cent, in the per cent of the total exchangeable. There are about an equal number of increases and decreases with the mean values for both cropped and virgin soils indicating very little change in the per cent of the total potassium exchangeable. The per cent of the total potassium exchangeable ranges from 0.11 per cent in cropped Plainfield loamy sand to 0.58 per cent in cropped Ontonagon clay. The mean values for the per cent of the total sodium exchangeable show a lh.8 per cent increase in the cropped soil. Since the error of the determination of sodium and potassium falls on the sodium determination this is not considered very significant. There are about an equal number of increases and decreases in the crOpoed soils. The data in Table 2 show very little change in the saturation capacity of these soils after continued cultivation. Wide variations have been noted in certain types while little difference was found in others. Since the mean values for the per cent of the bases exchangeable is nearly constant, it seems likely that there is an equilibrium between the bases in the exchangeable form and non—exchangeable form. This means there is a continuous change between the two forms of bases. This -20... change is probably very slow. The per cent of the total bases exchangeable increases as the soil becomes heavier. This would be expected when we consider the sanly soils are very low in colloidal material, and that the limit of exchange ca_acity is much narrower. The mean values for the per cent of the total bases ex hangeable in both cropped and virgin soils are as follows: Calcium, 21.92; magnesium, n.56; potassium, 0.365; and sodium, 0.29 per cent. This means the average of these soils contains enough calcium to replace the present amount exchangeable four times, while the magnesium is capable of 22 replacements, potassium, 275, and the sodium, 3h5 replacements. -21- PER CENT OF THE TOTAL BASTS AVE PER CETT 0F TOTAL BASES EXCHA"GEA3LE COHPRISEE 0F DIFFERER; BASES The relative prOportions of the bases, calcium, magnesium, potassium, and sodium, constituting the total of these bases and exclangeable cations in the soils studied are given in Table h. That is, calcium constitutes 12.1 per cent of the total bases and 82.5 per cent of the exchangeable bases of cultivated Hillsdale sandy loam. Sodium constitutes the highest per cent of the total bases followed by potassium, calciUm, and magnesium in the order named. Calcium is predominant in the exchangeable cations followed by nagnesium, sodium, and potassium respectively. The ratio of the exchangeable cations is in good agreement with the findings of other investigators. In general, as the soils become heavier the relztive proportion of the total bases and exclangeable cations constituted by calcium decreases. The reverse of this is true for magnesium and potassium, :hile sodium shows little or no difference. The difference between cropped and virgin soils shown in Table M have already been discussed. AVAILABLE PHOSPHORUS. PER CELT OF ”CTAL PHOSPHORUS AVAILABLE AYD AVAILABILITY OF EXCHATbE£“77 CALCIUM The question may well be asked, Does the availability of the nutrient elements in these soils differ? In order to obtain some information on this question the available phosphorus was determined using Truog's method, and the readily available exchangeable calcium using the method of Parker and Pate. The results, together with the total phosphorus and total exchangeable calcium of the soils are given in Table 5. The phosphorus is expressed in ppm. and the per cent of the total phosphorus that is readily available calculated. The calcium is expressed in milliequivalents and the per cent readily available phos- phorus as shown in Table 5 includes some of the difficultly available phosphorus. The amount of available phosphorus is rather low when all types are considered, ranging from 13 ppm. in virgin Miami loam.to 6H ppm. in virgin Coloma loamy sand. The per cent of the total phosphorus avail- able ranges from 2.69 per cent in cultivated xiami loam to 12.7 per cent in virg n Coloma loamy sand. .A factor which probably causes a low amount of available phosphorus to be present in these soils is the high hydrogen ion concentration. with the exception of cultivated and virgin Coloma loamy sand and virgin Plainfield loamy sand the quantity of readily available phosphorus in these soils would be considered below the minimum limit for general farmi 0. The amount of readily available phosphorus follows the total phosphorus content to a fair degree in these soils. With one exception, Ontonagon clay, the per cent of the total phOSphorus readily available -23- is greater in the virgin soil of each type. It is probable the availability of the exchangeable bases in a soil is important in the nutrition of plants. The lack of replacement from the absorbing complex of the soil might be related to the planvs response to these bases. The method of Parker and Pate ('19) for estimating the availability of exchangeable calcium is based on this principle. In this method equal quantities of exchangeable calcium and potassium in potassium acetate compete for the absorbing complex of the soil. The per cent of the exchangeable calcium found readily available by this method ranges from 10.36 per cent in the virgin College farm soil to 17.62 per cent in the cultivated Xiami lost. In all types studied the per cent of exchangeable calcium readily available was found to be greater in the cultivated soil. Due to the fact that the vdrogen ion concentrationsof these soils are grouped so closely it is impossible to determine if there is any relationship between the hydrogen ion con- centration and readily available exchangeable calcium. The results ob— tained on these soils indicate that the exchangeable calcium is more closely held in the absorbing complex of the virgin soils. -2h- CROP YIELDS OX CULEIVATiD ACE VIRQIE SOILS It was felt that it would be of interest to grow crops on the different cultivated and virgin soils studied in the laboratory. In some instances very small differences were found in the chemical studies between the cultivated soil and the correspondizg virgin soil. The possibility that a difference or differences not detected by the chemical methods used might be shown by plant growth seemed reasonable. With this in view the soil types of which there was a.sufficient quantity of the original samples were potted and seeded to barley. Due to an insufficient amount of soil only four sets of pots were possible for each soil. These pots were treated in duplicate as follows: (1) no treatment, (2) MOO pounds of 20% superphosphate per acre, (3) #00 pounds of 20% superphosphate and 200 pounds of sodium.nitrate per acre, (M) “00 pounds of 20% superphosphate, 200 pounds of sodium nitrate, and 100 pounds of muriate of potash per acre. The results obtained with the crop of barl ' are given in grams of air dry material in Table 6. When the treatments are considered as a group there is only one instance where the cultivated soil gave a higher yield than the virgin soil under similar conditions. In the Hiami checks the cropped soil gave a greater yield than the virgin soil. In the checks of the other soil types the virgin soil gave increases ranging from h.2 per cent in College Farm soil to 68 per cent in Coloma over the cropped soil. The average increase of the virgin checks over the cropped checks was 22.8 per cent. The pots which received #00 pounds of 20 per cent superphospldte per acre show that neither the crOpped or virgin soil of the Plainfield or Coloma types responds to phosphorus alone. This would be expected L Q from the results found in laboratory detbrulnfltlons of readily rvail- able phosphorus by the Truog method. By this method these two types were the only ones that indicated a sufficient amount of readily avail- able phosphorus for plant growth. The results of the determination of readily available phosphorus is well supported by the greenhouse results. The four soils of the Coloma and Plainfield types gave no increase for phosphorus when tne average was taken, while the six soils of the College Farm, hiami, and Hillsdale types gave increases ranging from 17 per cent in Miami crOpped to 55.8 per cent in hiami virgin with an average increase of 31.N per cent for phosphorus treatment. The virgin soils gave a greater response to phosphorus treatment than did the cropped soils. The average increase for the virgin soils over the checks, in the three soil types which responded to the treat- ment being M3 per cent and that of the cropped soils 20 per cent. The phosphorus treated virgin soils outyielded the similarly treated cropped soils of all types. The increase of the virgin over the cropped soils ranging from 5 per cent on the Plainfield soil to 65 per cent on the Coloma soil with an average increase of 30.7 per cent. Both the cropped and virgin soils responded to nitrogen fertilization, the cropped soils giving a.much greater response. Where 200 pounds of sodium nitrate per acre was applied in addition to the MOO pounds of super- phosphate per acre marked increase in growth was noted. The per cent increased growth amounted to an average of h6.5 per cent on the cropped soils over the corresponding soil receiving phosphate alone, ranging from ‘ 6.5 per cent on cropped Miami to 89 per cent on cropped Plainfield. The -25- average yield on the virgin soils was 23 per cent greater for the nitrogen- phosphorus pots than the corresponding treatments of phosphorus alone. As in the cropped soils all virgin soils showed better growth when nitro en was applied with phosphorus, however, the crOpped soils gave a considerably greater response to nitrogen. This is shown by the average increase over the phosphorus treatment and also by the differezce in the similrrly treated cropped and virgin soils. The nitrogen-phosphorus treated virgin soils gave an average of 7.5 per cent more plant growth than the nitroren- phosphorus treated crOpped soils. In the phosphorus series the virgin had an average of 30.5 per cent more plant growth. The virgin soils gave a greater response to phosphorus while cropped soils gave a much greater response to nitrogen. The greater plant growth on the cropped soils due to nitrogen is probably due to the organic matter of those soils having reached a slower rate of decay and therefore not liberating nitrogen as rapidly. This seems to be the most likely explanation as in some cases little difference in the total nitrogen content is found. The greater response of the cropped soils to nitrogen is shown again when the checks are compared with the nitrogen-phosphorus treatment. The cropped soils receiving nitrogen and phosphorus gave an average of 66 per cent more plant growth than the checks while the virgin soils having a similar treatment gave M9 per cent more plant growth than the checks. When 100 pounds of muriate of potash was applied per acre in addition to MOO pounds of 20 per cent superphosphate and 200 pounds of sodium nitrate varied results were obtained. Three of the five cropped soils and one of the virgin soils gave a decrease in plant growth when compared with the nitrogen-phosphorus treatment. The ranre of the yields on the cropped soils being from a decrease of h per cent on Coloma to an increase of 11 per cent on Plainfield, while the virgin soil gave a yield ranging from -27- a decrease of 2 per cent on Hillsdele to an incr ase of 20 per cent on Plainfield. The average for the complete fertilizer was a 2 per cent increase on ropped soils and 10 per cent on virgin soils over the nitroyen-phosphorus series. When compared with the check', very marked increases are obtained by the use of a.complete fertilizer. The cropped soils with a complete fertilizer outyielded the checks in all cases, ranging from 32 per cent on Hiami to 111 per cent on Plainfield, while on the virgin soils Coloma gave the least increase and Plainfield the greatest, ranging from 32 per cent to 105 per cent. The virgin soils receiving a complete fertilizer gave 10.5 per cent more growth than the cropped soils with similar treatment. -25- 1‘71- :1: A‘Vr ,- Aura nA-vrwfi'qufnwvm H , 1 “kl-“o““kl in!“ V"‘V‘-J.VU“~JLI The chemical composition of cropped and the corresponding virgin soil of several different soil types was determined. With the exception of nitrogen content, which, with one exception, was higher in the virgin soils a comparison of analyses of cropped and virgin soils showed no consistent differences. In many instances, wide differences in the quantities of certain elements are noted within a given soil type. In the lighter soil types phosphorus has been decreased by cropping. In the heavier soil types phosphorus has been increasei by cropping. Exchangeable hydrogen, aluminum, manranese, calcium, magnesium, sodium, potassium, ammonium, absorption capacity and pH were determined. Very small differences were found in the exchang;able hydrogen of cropped and virgin soils. ihere has been no change in p3 due to cropping. The content of the exchangeable bases calcium, magnesium, sodium, and potassiUm vary widely in the different soils. t?mn.each type is considered separately, however, the mean value indicates that the bases -have remained fairly constant. Five types indicate an increase in base capacity and total bases in the cropped soils, while two indicate a decrease. The per cent of the total bases exchangeable increases as the soil becomes heavier. As the texture of the soil becomes finer the relative proportion of the total bases and exchangeable cations constituted by calcium decreases. With one exception the per cent of the total phosphorus readily available was greater in the virgin soils. In all types studied the per cent of exchangeable calcium readily available was found to be greater in the cultiv;ted soil. This indicates that the calcium.is held more firmly by the absorbin. complex of the virgin soils. The virgin soils gave greater plant grOYth under all treatments than did the cropped soils with similar treatments. Virgin checks {ave an average increase of 22.8 per cent plant growth over cropped checks. Plant responses to phosphorus were in good agreement with laboratory determinations of readily available phosphorus. The cropped soils gave the greater response to nitrogen fertilization. The virgin soils gave the greater response to phosphorus fertilization. 2. 3e 9. 10. 11. 12. 130 111». REFERENCES Ames, J. v., and Schollenberger, c. J. 1919. Calcium and magnesium content of virgin and cultivated soils. Soil Sci. 8: 323 - 335. Association of Official Agricultural Chemists. 1925. Methods of analysis. ed. 2. Washington, D. c. Banr, L. D. 1926. The use of the quinlwdrone electrode for measuring the hydrogen ion concentration of soils. Soil Sci. 21: 167 - 179. Crowther, E. L, and 3am. J. K. 1931. Studies on soil ' reactions VIII. The influence of fertilizers .and lime on the replaceable bases of a. light acid soil after fift}r years of continuous crop- ping with barley and wheat. Jour. Agri. Sci. 21: 689 - 715. Preps, G. S. 1929. Relation of water soluble potash, the replaceable. and acid soluble potash to the potash removed by crops in pot experiments. Texas Agr. Exp. Ste. 3111. 391. pp. 18. Gedroiz, K. K. 1931. Exchangeable cations of the soil and the plant. 1 Relation of plant to certain cations fully saturating the exchange capacity. Soil Sci. 32: 51 - 63. Glinka. K. D. 1925. Annals of the state institute of experimental agrenonw (Leningrad) 3: 1. Handy, J. O. 1900‘. The volumetric determination of magnesia. Jour. Amer. Chem. Soc. 22: 31 - 39. Hissink. D. J. 192M. Base exchange in soils. Trans. Faraday Soc. 20: 551 - 556. —— ibid (original not seen). Kelly, 1!. P.. and Brown, 8. M. 1921!. Replaceable bases in soils. Calif. Agr. Exp. Sta. Tech. paper 15. Martin, J. O. 1929. The effect of crop growth on the replaceable bases in some California soils. Soil Sci. 27: 123 - 136. McLean, L. and lobinson, G. I. 1921+. A new method for determining amnenical nitrogen in soils. Jour..Agr. Sci. 1n: 5M8 - 55h. Metzger. W. H. 1929. The effect of moisture content and capping on exchangeable calcium and magnesium. with particular reference to rice soils. Soil Sci. 27: 305 - 318. . . _ ' I I O 0 i o ' o P- . O C I o I ‘ I ' ' o . . . \. . . . v .. —- ' O . D . . . ~ 9 . t O I . o .1 ‘ b O I ‘ ‘ .. q. I »- » > -’ - . . . . . . I - . , . I .— 0 v a . l A n - s » , Q - . ,1 . . ‘ ' . ’ § , . — ' I . Q o o o - o . . s .- - . . hi. . I 0 I ' I O ' l , _ ' ., . , . .- . D I ' : O I I 0 g b I c C ‘ - I . . F ' ' ._.. o O + ~ I o 7 I - O I ' . . . - _ . V o O § o O r r - 4 _ , . . . ‘ , , I n o — . . ~__..._.._.--_~. ——c-—..._... 150 16. 17. 18. 19. 21. 22. 23. 2h. 25. 26. REFERENCES (Continued) Miller, C. E. 1923. Studies on virgin and depleted 30118. 3011 Sci. 16: u;; - the. Miramanoff, K. H. P. 1930. Influence of alfalfa on the change of virgin soils in the cotton districts of Armenia. Jour. Amer. Soc. Agron. 22: 97 - 107. Ogg, W. G., and Dow, W. T. 1928. The reaction, exchangeable calcium and lime requirement of certain Scottish soils. Jour. Agr. Sci. 18: Part 1: 131 - 157. Page, H. J., and Williams, W. 1924. Studies on base exchange in Rothanstead soils. Trans. Faraday Soc. 20: 573 - 585. Parker, F. l. and Pate, w. w. 1926. Base exchange in 3011. colloids and the availability of exchangeable calcium in different soils. - Jour. Amer. Soc. Agron. 18: 1#70. Schollenberger, C. J. 1927. Exchangeable hydrogen and soil reaction. Science 65: 552 - 553. —- v - and Dreibilbis, 1'. R. 1930. Effect of cropping with various fertilizer, manure, and lime treat- ments upon the exchangeable bases of plot soils. Soil Sci. 29: 371 - 39h. - — 1930. Analytical methods in base exchange in- vestigations on soils. Soil Sci. 31: 161 - 173. Scott, W. W. 192 . Standard methods of chemical analysis. ed. . pp. 1#10. New York. Swanson, G. 0. and Latshas, I. L. 1919. Effect of alfalfa on the fertility elements of the soil in com- parison with grain crops. Soil Sci. 8: l - 39. Truog, Emil. 1930. The determination of readily available phosphorus of soils. Jour. Amer. Soc. Agron. 22: 87h - 882. Iilson, BenJamin D. 1930. Exchangeable calcium and potas- eium in soils as affected by cropping and ferti- lization. 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