Chapter 6, It Being No. 219 of the Table on P. 98.

Strength of Acid used.—Three different strengths of acid were simultaneously employed, viz., chlorhydric of 1.10, 1.115 and 1.160 density. With these the soil was digested at steam heat in porcelain beakers covered with watch glasses for five days each, then evaporated and analyzed as usual. The results were as follows:

ANALYSIS WITH ACID OF DIFFERENT STRENGTHS. =========================+========================= Ingredients. | Sp. G. of Acid. -------------------------+--------+--------+------- | 1.10 | 1.115 | 1.160 +--------+--------+------- Insoluble residue | 71.88 | 70.53 | 74.15 Soluble silica | 11.38 | 12.30 | 9.42 Potash | .60 | .63 | .48 Soda | .13 | .09 | .35 Lime | .27 | .27 | .23 Magnesia | .45 | .45 | .45 Br. ox. Manganese | .06 | .06 | .06 Ferric Oxid | 5.15 | 5.11 | 5.04 Alumina | 6.84 | 8.09 | 6.22 Sulfuric acid | .02 | .02 | .02 Volatile matter | 3.14 | 3.14 | 3.14 | ------ | ------ | ----- | 100.02 | 100.69 | 99.29 | | | Amount of soluble matter | 24.00 | 27.02 | 22.27 Amount of soluble bases | 13.50 | 14.70 | 12.83 -------------------------+--------+--------+-------

It will be noted that the strongest acid produced the smallest amount of decomposition of the soil silicates, e. g. the silica soluble in carbonate of soda solution being 3% less than in the case of the acid of medium strength; a result possibly due to some difficultly-soluble compound formed on the surface of the soil grains. The weakest acid had a stronger solvent power; but the maximum effect was produced by the acid of 1.115 density. This being also the most readily obtainable, by simple steam distillation of acid of any other strength, the writer adopted it as best suited to the purposes of soil analysis.

To ascertain the time required for the desired action, viz., the solution of the plant-food ingredients to the extent likely to be of any avail to growing plants, digestions of the same soil were made in the same manner for periods of 1, 3, 4, 5 and 10 days, with the acid of 1.115 density. The results were as follows:

ANALYSIS AFTER DIFFERENT TIMES OF DIGESTION. =========================+================================== | No. of Days’ Digestion. Ingredients. +------+------+------+------+------ | 1 | 3 | 4 | 5 | 10 -------------------------+------+------+------+------+------ Insoluble Residue | 76.97| 72.66| 71.86| 70.53| 71.79 Soluble Silica | 8.60| 11.18| 11.64| 12.30| 10.96 Potash | .35| .44| .57| .63| .62 Soda | .06| .06| .03| .09| .28 Lime | .26| .29| .28| .27| .27 Magnesia | .42| .44| .47| .45| .44 Br. Ox. Manganese | .04| .06| .06| .06| .06 Ferric Oxid | 4.77| 5.01| 5.43| 5.11| 4.85 Alumina | 5.15| 7.38| 7.07| 7.88| 7.16 Phosphoric acid | .21| .21| .21| .21| .21 Sulfuric acid | .02| .02| .02| .02| .02 Volatile matter | 3.14| 3.14| 3.14| 3.14| 3.14 +------+------+------+------+------ Total | 99.63|100.68|100.55|100.69| 99.80 | Amount of soluble matter | 19.67| 24.88| 25.57| 27.02| 24.87 Amount of soluble bases | 11.05| 13.68| 13.91| 14.49| 13.68 -------------------------+------+------+------+------+------

While these results pointed clearly to the five-day period as being sufficiently effective so far as the plant-food ingredients are concerned, it was not easy to understand why a ten-day digestion should be less incisive than a five-day one. Instead of repeating the ten-day experiment, it was thought preferable to re-treat the residue from the five-day digestion for five days more. The result was that only more silica and alumina went into solution—in other words, additional clay was alone being decomposed. This being of no interest in the matter of plant nutrition, the five-day period was definitely adopted by the writer for his work; and it, together with the acid of 1.115 density, is the basis of all the results given in this volume, except where otherwise stated. There appeared to him to be no good reason for the acceptance of the arbitrary method of soil-extraction suggested by Kedzie and since adopted by the Association of Official Agricultural Chemists; the more as to do so would throw out of comparison all the previous work done by Owen, Peter, and himself and his pupils, which had already been definitely correlated with the natural conditions and with cultural experience.

While regretting to thus “secede” from the fellowship of his colleagues, the writer cannot but regret equally their voluntary decision to do over again, or lightly reject, all that had been done before in correlating soil-composition and plant-growth. He still thinks that it is idle to expect any unification, national or international, of methods of soil analysis based upon purely arbitrary prescriptions, unless previously shown to be definitely correlated with natural and cultural conditions; as is measurably the case with Dyer’s method.

Virgin Soils with High Plant-food Percentages are Always Productive.—In strong contrast to the contradictory evidence deduced from the analysis, by any method, of cultivated soils when compared with cultural experience, it seems to be generally true that virgin soils showing high percentages of plant-food as ascertained by extraction with strong acids (such as hydrochloric, nitric, etc.), invariably prove highly productive: provided only that extreme physical characters do not interfere with normal plant growth, as is sometimes the case with heavy clays, or very coarse sandy lands.—To this rule no exception has thus far been found. The composition of some representative soils falling within this category is given in the annexed table, which at the same time conveys some idea of the proportion of acid-soluble ingredients usually found in the best class of natural soils.

TABLE EXEMPLIFYING HIGH PLANT-FOOD PERCENTAGE IN SOILS.

(A) = Buckshot soil. Yazoo Bottom. (B) = Black Prairie. Rankin County. (C) = Loamy Sediment. Houma, Terrebonne parish. (D) = Rio Grande Bottom. Sandy Sediment. ============================+===================+==========+========= | Mississippi |Louisiana.| Texas. +---------+---------+----------+--------- | | | | | (A) | (B) | (C) | (D) | (Heavy Clay). | (Loam). | ----------------------------+---------+---------+----------+--------- Number of Sample | 390 | 188 | 240 | 37 ----------------------------+---------+---------+----------+--------- Chemical Analysis of | | | | Fine Earth. | | | | Insoluble matter | 51.06 | 69.95 | 35.48 | 36.04 | 71.77| 74.40| 56.24 | 53.30 Soluble silica | 20.70 | 4.46 | 20.76 | 17.26 ----------------------------+---------+---------+----------+--------- Potash (K₂O) | 1.10 | .90 | 1.03 | 1.31 Soda (Na₂O) | .33 | .24 | .13 | .22 Lime (CaO) | 1.35 | 1.04 | .72 | 14.43 Magnesia (MgO) | 1.67 | .91 | .88 | 1.53 Br. ox. of Manganese (Mn₃O₄)| .12 | .12 | .014 | .07 Peroxid of Iron (Fe₂O₃) | 5.82 | 4.77 | 7.10 | 4.09 Alumina (Al₂O₃) | 10.54 | 7.25 | 15.45 | 9.11 Phosphoric acid (P₂O₅) | .30 | .47 | .15 | .20 Sulfuric acid (SO₃) | .02 | .16 | .25 | .04 Carbonic acid (CO₂) | | | | 9.91 Water and organic matter | 7.37 | 10.74 | 18.52 | ? ----------------------------+---------+---------+----------+--------- Total |100.38 |101.01 |100.48 |100.22 ----------------------------+---------+---------+----------+---------

(E) = San Diego Co. Colorado Bottom. Silt Sediment. (F) = Riverside Co. Palm Valley. Micaceous Sandy Soil. (G) = Tulare Co. Experiment Station. Plains Loam. (H) = Solano Co. Putah Valley. Dark Loam. (I) = San Luis Obispo Co. Arroyo Grande Dark Loam. ============================+========================================= | California. +---------+------+------+--------+-------- | | | | | | (E) | (F) | (G) | (H) | (I) | | | | | ----------------------------+---------+------+------+--------+-------- Number of Sample | 506 | 1092 | 1159 | 110 | 2061 ----------------------------+---------+------+------+--------+-------- Chemical Analysis of | | | | | Fine Earth. | | | | | Insoluble matter | 58.57 | 71.45| 72.98|67.33 |53.43 | 63.90| | | 71.00| 72.43 Soluble silica | 5.33 | 5.50| 6.60| 3.67 |19.00 ----------------------------+---------+------+------+--------+-------- Potash (K₂O) | 1.18 | 1.42| 1.20| .93 | .67 Soda (Na₂O) | .16 | .18| .52| .12 | .18 Lime (CaO) | 8.67 | 2.20| 1.86| .77 | 2.11 Magnesia (MgO) | 2.97 | 2.09| 1.81| 2.29 | 2.26 Br. ox. of Manganese (Mn₃O₄)| .03 | .05| .08| .11 | .06 Peroxid of Iron (Fe₂O₃) | 4.14 | 6.68| 6.86| 8.01 | 5.23 Alumina (Al₂O₃) | 8.40 | 5.78| 5.66| 9.16 | 7.40 Phosphoric acid (P₂O₅) | .13 | .35| .10| .11 | .71 Sulfuric acid (SO₃) | .15 | .01| .03| .12 | .22 Carbonic acid (CO₂) | 7.82 | .18| | | 1.82 Water and organic matter | 3.34 | 4.29| 2.54| 7.12 | 6.63 ----------------------------+---------+------+------+--------+-------- Total |100.89 |100.18|100.24|99.74 | 99.72 | | | | | Humus | | | | | 3.06 Nitrogen in humus | | | | | 22.00 Nitrogen in soil | | | | | .67 Hygroscopic moisture. | | | | | absorbed at 15°C | | | | | 10.70 ----------------------------+---------+------+------+--------+-------- Available phos. acid .14 Available potash .14

The Rio Grande and Colorado bottom soils contain amounts of lime carbonate largely in excess of requirements, 2 to 3% of that compound being all that is needed to insure all the advantageous effects of lime in any soil (see this chapter, page 367).

Discussion of Table.—It will be noted in this table that while the total of the matters soluble in acids (inclusive of silica) ranges from a little below 50 to over 77 per cent, the total of directly important mineral plant-food ingredients (potash, lime, magnesia and phosphoric acid), constitute in moderately calcareous soils only from about 2.5 to somewhat over four per cent of the whole. Yet if all these were in available form, the supply would be abundant for many hundreds and even thousands of crop years. For, one-tenth of one per cent in the case of the clayey soils of the preceding table would amount to about 3500 pounds per acre-foot, and to 4000 in the case of the sandy ones. Hence the amount of phosphoric acid in e. g., the Mississippi delta soil from Houma would suffice for the production of about 440 crops of wheat grain (at 20 bushels per acre) if only one foot depth were drawn upon; but as the roots of grain easily penetrate to twice and half and three times that depth even in the humid region, the number might be tripled. As a matter of fact, however, that soil has produced full crops for from forty to fifty years only; yet this is considered an exceptionally long duration of profitable production without fertilization.

The first and last soils in the above list represent probably the highest types of productiveness known. The Yazoo bottom soil has produced up to one thousand pounds of cotton lint per acre when fresh, and is still producing from four to five hundred pounds after thirty years’ culture. The Arroyo Grande soil of California with its extraordinary percentages of phosphoric acid and nitrogen, as well as exceptionally high proportion of available phosphoric acid and potash, has made such a record of productiveness, and high quality of the seeds produced, that it has for a number of years been excluded from competition for prizes offered by seed-producers elsewhere, in order to give other sections a chance. Both these soils are rather heavy clays, but readily tillable in consequence of their abundant lime-content. The remarkably high content of acid-soluble silica, indicating the presence of much easily available zeolitic matter, is doubtless connected with the exceptional productiveness.

Experience, then, proves that lands showing such high plant-food percentages will yield profitable harvests for a long time without fertilization, or with only such partial returns as are afforded by the offal of crops. Also that when fertilization comes to be required, instead of supplying all the ingredients usually constituting fertilizers, only one or two of these will as a rule be actually needed, and even these in smaller amounts than in “poor” lands; thus materially reducing the expense of fertilization. The high production and durability of such lands therefore amply justify their higher pecuniary valuation; for which there would be no rational permanent ground if they required fertilization to the same extent as poor lands. In other words, if the entire amount of soil-ingredients removed by crops had had to be currently replaced equally in all cases (as is implied in the hypothesis, advanced by some, that the chemical composition of soils is of no practical consequence), the high prices which from time immemorial have been paid for black prairie and rich alluvial lands as against meagre uplands and barrens, would have been so much money wasted.

The explanation of these advantages evidently lies largely in the larger amounts of soil ingredients annually rendered available in rich soils by the fallowing effect of the atmospheric agencies, because of the generous totals present. The actual amounts of soil ingredients thus rendered accessible to plants, other things being equal, are evidently more or less directly proportional to the totals of acid-soluble plant-food ingredients present. And if this is true in cultivated lands, the inevitable conclusion is that the same must be true of virgin lands; whose productive capacity and duration can therefore be forecast by such analyses. It will be observed that the above data, which could be indefinitely increased by corroborative analyses, seem to establish the fact that about one per cent of acid-soluble potash, one of lime, the same, or less, of magnesia, and .15% of phosphoric acid, are thus shown to be “high” percentages of these ingredients in virgin soils.

It is not easy to see how the above conclusions can be successfully controverted; they are, moreover, thoroughly in accordance with cultural experience. Difficulties of interpretation arise mainly in the case of medium soils, which show neither very high nor very low percentages of plant-food; and which raise the question of what amount or percentage constitutes “adequacy” of each of the several substances.

Low Percentages.—On the other hand, whenever in virgin soils acid-analysis shows the presence of but a very small proportion of one or several of the essential ingredients, we have a valuable indication as to the one of these that will first be required to be added when production slackens.

What are “Adequate” Percentages of Potash, Lime, Phosphoric Acid and Nitrogen?—It is evident that a very critical discussion of cultural experience can alone answer this question; and at first sight such experience often appears very contradictory when compared with the results of analysis.

One of the chief causes of such apparent discrepancies is readily intelligible when we consider the differences in root-development of the same plant in different soils. In “light” or sandy lands the roots may penetrate to several times the depth attained by them in heavy clay soils. Having thus within their reach a soil-mass several times larger, and aerated to a much greater depth, it is but reasonable to expect that in deep, sandy lands plants would do equally well with correspondingly smaller percentages of plant-food than would suffice in clay soils, in which the root-range is very much more restricted. The well-known fact that the production of heavy clay lands may be increased by their intermixture with mere sand, adding nothing to their store of plant-food, emphasizes this expectation and elevates it into a maxim. On this ground alone, therefore, it is evident that the mere consideration of plant-food percentages found, can be a true measure of productiveness only in the case of virgin soils with high percentages.

Soil Dilution Experiments.—The extent to which dilution with mere “lightening” materials can be carried without impairing production, can of course be determined for concrete cases only; but the following experiment made at the California Station is a case in point:

One kilogram of the heavy but highly productive black clay soil of the experimental grounds of the University of California was used in each of five experimental cultures, each made in duplicate, in cylindrical vessels of zinc-covered (“galvanized”) sheet iron, all proportioned alike in height and diameter, but containing respectively one, two, four, five and six volumes of total soil. In the smallest was placed one kilogram of the undiluted, original soil, in the others successively the same amount of the soil thoroughly mixed with one, three, four, and five volumes of a dune sand fully extracted with chlorhydric acid, and washed with distilled water. The water capacity of each of the mixtures was determined and the earth in the pots kept at the point of half-saturation generally admitted to be the optimum (best condition) for plant growth. Each pot was sown with ten seeds of white mustard, subsequently reduced to five plants selected for their vigor.

DEVELOPMENT OF ROOTS OF WHITE MUSTARD IN CLAY SOIL, DILUTED WITH VARIOUS PROPORTIONS OF PURE SAND.]

The (“galvanized”) vegetation pots were made as nearly as possible of similar proportions in depth and width for each dilution, so as to give opportunity for the proportional development of the root systems. The photographs show the latter as nearly as practicable in their natural form, restored after washing off the adherent soil. It was of course extremely difficult to preserve intact the extreme circumferential rootlets and hairs; yet the general development is correctly shown.

The following table shows the percentage composition of the original as well as the diluted soils, while the photographs show the development of the plants in their successive stages, so far as these could be observed; the continued attacks of mildew and plant lice preventing full maturity being attained.

COMPOSITION OF BLACK ADOBE AND SAND DILUTIONS. ============================+========+============================== |Original| Dilutions. Chemical analysis of | soil. | fine earth. | 1:0 | 1:1 1:3 1:4 1:5 ----------------------------+--------+-------+-------+-------+------ Insoluble matter | 54.50 | 77.25 | 88.62 | 90.00 | 92.42 Soluble silica | 19.60 | 9.50 | 4.75 | 3.80 | 3.17 Potash (K₂O) | .73 | .36 | .18 | .15 | .12 Soda (Na₂O) | .20 | .10 | .05 | .04 | .03 Lime (CaO) | 1.15 | .57 | .29 | .23 | .19 Magnesia (MgO) | 1.08 | .54 | .27 | .22 | .18 Br. ox. of Manganese (Mn₃O₄)| .04 | .02 | .01 | .01 | .01 Peroxid of Iron (Fe₂O₃) | 8.43 | 4.22 | 2.11 | 1.68 | 1.40 Alumina (Al₂O₃) | 7.92 | 3.96 | 1.98 | 1.58 | 1.32 Phosphoric acid (P₂O₅) | .19 | .10 | .05 | .04 | .03 Sulfuric acid (SO₃) | .04 | .02 | .01 | .01 | .01 Carbonic acid (CO₂) | | | | | Water and organic matter | 6.54 | 3.27 | 1.64 | 1.31 | 1.09 Loss in analysis | 1.18 | .09 | .04 | .03 | .03 +--------+-------+-------+-------+------ Total | 100.00 |100.00 |100.00 |100.00 |100.00 | | | | | Humus | 1.21 | .60 | .30 | .24 | .20 “ Ash | .94 | .47 | .23 | .19 | .16 “ Nitrogen, p. cent | | | | | in Humus | 18.58 | 18.58 | 18.50 | 18.58 | 18.58 “ “ p. cent. | | | | | in soil | .203| .10 | .05 | .04 | .034 ----------------------------+--------+-------+-------+-------+------

The restricted volume of soil occupied by the roots in the undiluted adobe soil, together with the very abundant development of root-hairs, is very striking. A marked change in these respects is manifest in the first dilution, and increasingly so as dilution increases; the paucity of root-hairs is very marked in the last (greatest) dilution, in which, as the photograph of the plants shows, the development was decidedly behind that in the pot containing dilution 1:4. The latter in fact showed the best development not only in this case, but in two other series of tests conducted at the same and subsequent times; and strangely enough, also in the pulverulent, “sandy loam” soil of the southern California substation tract. In the latter series, which for lack of space cannot be figured here, the main difference was that in the undiluted soil the roots filled the entire soil mass, instead of remaining near the surface, as in the pure adobe. It is possible that the latter was too wet when given the full half of its water-capacity, although, as the figures show, the water was slowly introduced from below by means of glass tubes, ending within a shield to prevent puddling.

Limitation of Root Action.—These results, representing five soils of different percentage-composition and physical character, but identical chemical composition and ratios between the several ingredients, and similarly acted upon by the atmospheric agencies in the past, illustrate strikingly the impossibility of judging correctly of a soil’s productiveness from percentages of chemical ingredients alone. It is clear that the physical characters of the land as well as its depth, must be essentially taken into account. But there is obviously a certain limit beyond which greater perviousness and root-penetration cannot make up for deficiency in the absolute amounts of plant-food within possible reach of the plant; for in the case of excessive dilution these are rendered partially inaccessible within the time-limits of a season’s growth.

It is hardly necessary to say that these experiments require repetition with the aid of the experience acquired in these first trials, not only in the laboratory but also in the field. It will be especially interesting to compare with the results obtained in these strongly calcareous soils, the effects of dilution in such soils as those of Florida, mentioned below; the probability being that where lime is naturally deficient, the effects of dilution will be much more pronounced in diminishing production, because of the absence of the previous favorable action of lime upon the availability of the soil-ingredients.

Lowest Limit of Plant-food Percentages and Productiveness found in Virgin Soils.—The subjoined table shows some of the very low plant-food percentages found in natural soils, all being of a sandy character:

============================+==================================== | MISSISSIPPI SOILS. +----------+--------+--------+------- |Homochitto| Shell | Pine | Pine | Bottom. |Hammock.| Woods. |Flats. ----------------------------+----------+--------+--------+------- Number of Sample. | 68 | 83 | 206 | 214 ----------------------------+----------+--------+--------+------- CHEMICAL ANALYSIS OF | | | | FINE EARTH. | | | | ----------------------------+----------+--------+--------+------ Insoluble matter | | | | | 92.16 | 96.08 | 93.23 | 95.59 Soluble silica | | | | ----------------------------+----------+--------+--------+------ Potash (K₂O) | .15 | .05 | .26 | .06 Soda (Na₂O) | .04 | .06 | .07 | .05 Lime (CaO) | .12 | .10 | .12 | .02 Magnesia (MgO) | .21 | .12 | .18 | .07 Br. ox. of Manganese (Mn₃O₄)| .28 | .05 | .15 | .05 Peroxid of Iron (Fe₂O₃) | 1.18 | .52 | 1.25 | .46 Alumina (Al₂O₃) | 3.22 | .46 | 2.36 | .85 Phosphoric acid (P₂O₅) | .08 | .10 | .03 | .02 Sulfuric acid (SO₃) | .05 | Trace | .02 | Trace Carbonic acid (CO₂) | | | | Water and organic matter | 2.70 | 3.02 | 2.33 | 2.28 +----------+--------+--------+-------- Total | 100.19 | 100.56 | 100.00 | 99.45 ----------------------------+----------+--------+--------+--------

============================+==================== | FLORIDA SOILS. +-------------------- | Pine Lands. |-------+------------ | First | Second |Class. | Class. ----------------------------+-------+------------ Number of Sample. | 6 | 7 ----------------------------+-------+------------ CHEMICAL ANALYSIS OF | | FINE EARTH. | | ----------------------------+-------+------------ Insoluble matter | 94.46 | 95.63 | | 96.51 Soluble silica | 1.67 | .88 ----------------------------+-------+------------ Potash (K₂O) | .19 | .12 Soda (Na₂O) | .04 | .06 Lime (CaO) | .07 | .06 Magnesia (MgO) | .04 | .04 Br. ox. of Manganese (Mn₃O₄)| .06 | .05 Peroxid of Iron (Fe₂O₃) | .32 | .22 Alumina (Al₂O₃) | .92 | .47 Phosphoric acid (P₂O₅) | .11 | .09 Sulfuric acid (SO₃) | .09 | .06 Carbonic acid (CO₂) | | Water and organic matter | 1.88 | 1.81 +-------+------------ Total | 99.85 | 99.49 ----------------------------+-------+------------

The average of plant-food percentages in all these soils is quite low, and at first sight there seems to be little choice between them. Yet two of them—Nos. 68 and 88, from Mississippi—are not only quite productive at the outset, but also fairly durable. This becomes measurably intelligible when it is known that both are of great depth, and so well drained that roots can descend for many feet; while the composition of the soil-material is almost identical for three or four feet. On the other hand, both Nos. 206 and 214 are quite shallow, being underlaid by sand almost devoid of plant-food at about two feet. In addition, both have extremely low percentages of phosphoric acid; while the rest show near .10% of that ingredient, an amount which, as will be seen hereafter, is considerably above the recognized limit of deficiency. The two Florida soils however bear only pine; they are underlaid by almost clean sand at two or three feet, and are therefore quickly exhausted. It will also be noted that their lime-percentage is only about half of that of the two first-named Mississippi soils, both of which bear a strong growth of deciduous timber trees, grape vines, and other vegetation indicating the presence of lime carbonate.

It is noteworthy, also, that the popular classification of the two Florida soils corresponds exactly with the differences in the percentages of plant-food; those in the “second-class” soil being uniformly lower than those in the one designated as first-class. This indicates, again, that as between soils of similar character and origin, the production and durability are sensibly proportional to the plant-food percentages when the latter fall below a certain limit; a point more fully illustrated farther on.

In the light of the above experiment and tables, it becomes pertinent to consider what are the lowest percentage limits of each of the more important plant-food ingredients compatible with profitable production.

LIMITS OF ADEQUACY OF THE SEVERAL PLANT-FOODS IN VIRGIN SOILS.

It is obvious that the lower limits of adequacy of the critical plant-food ingredients are best ascertained in the case of virgin soils containing very small amounts of some one ingredient, while fairly or fully supplied with the rest. In such cases, which are not at all infrequent, the use of the deficient ingredient as a fertilizer should produce a very marked effect so soon as the first flush of production (always noted in fresh soil) is over. This first productiveness may, even in poor lands, range from one to three years, when there is a sudden decline.

Lime a Dominant Factor.—When we investigate the cases of such lands, it soon becomes apparent that besides the low percentage of any one ingredient, the proportions of others present require consideration. Among these, lime in the form of carbonate stands foremost. Its presence exerts a dominant and beneficial influence in many respects, as is readily apparent from the prompt change in vegetation whenever it is introduced into soils deficient in it. In discussing the results of soil analysis, its consideration is of first importance in forecasting correctly the adequacy or inadequacy of other soil ingredients (see