CHAPTER XX.. Soils of the Arid and Humid[125] Regions.

SOILS OF THE ARID AND HUMID REGIONS.

Composition of Good Medium Soils.—In the preceding tables examples have been given of rather extreme types of soils, both rich and poor throughout, and also of such as are deficient in one or several of the important ingredients. In the table below are given the analyses of some of the good average farming lands; uplands of several states, both of the humid and arid regions. In the former, the representative timber trees of such lands are the black, red, white and (less characteristically) the post, black-jack, Spanish, overcup and locally some other oaks; grading higher in proportion to the presence of more or less hickory, and lower as the latter is replaced by pine. In the states south of Ohio, the “oak and hickory uplands” are what the farmer usually looks for, outside of the valleys or bottoms.

In the discussion in this chapter the “humid region” referred to is always that of the temperate zones, unless expressly otherwise stated. The most humid region of all—the tropics—is treated under a special head.

Criteria of Lands of the Two Regions.—In the country west of the Rocky Mountains, the timber, while locally very characteristic, cannot be as broadly used as a criterion, partly on account of its scarcity, partly because the dominant factor in the growth of trees is moisture, which is measurably independent of chemical soil-composition. The latter, moreover, on account of climatic conditions, already alluded to (chapter 16), does not vary as materially in the arid as the humid region, on account of the almost universal presence of larger proportions of lime carbonate; the variations of which in the humid region govern largely the vegetative changes. For we there find the timber growth of the lowlands ascending into the uplands so soon as the latter becomes decidedly calcareous; as is abundantly exemplified in the loess or “bluff” formations bordering the Mississippi, Ohio, and Missouri rivers, where the black walnut, tulip tree, ash, honey-locust, together with the lowland oaks, hickories and cane usually characterizing the stream bottoms, grow abundantly and with luxuriant development on the adjoining steep hill country as well (see below, chapters 24, 25).

UPLAND SOILS OF HUMID REGION. ==================================================================== OAK UPLANDS WITH HICKORY AND WALNUT. -----------------------+----------+---------------+--------+-------- State. |Tennessee.| Mississippi. |Alabama.|Georgia. | | | | -----------------------+----------+--------+------+--------+-------- County. |Rutherford|Pontotoc|Benton|Cherokee| Polk -----------------------+----------+--------+------+--------+-------- Number of Sample. | 7 | 226 | 216 | 110 | 502 -----------------------+----------+--------+------+--------+-------- ANALYSIS OF FINE EARTH.| | | | | | | | | | Insoluble matter |75.35 |83.27 | |78.73 |72.32 | 82.66 | 88.83|83.35 | 84.77| 76.55 Soluble silica | 7.31 | 5.56 | | 6.04 | 4.23 Potash (K₂O) | .26 | .37 | .55| .26 | .73 Soda (Na₂O) | .26 | .22 | .08| .12 | .17 Lime (CaO) | .34 | .28 | .25| .33 | .29 Magnesia (MgO) | .30 | .23 | .48| .40 | .26 -----------------------+----------+--------+------+--------+-------- Bro. ox. of Manganese | | | | | (Mn₃O₄) | .04 | .28 | .76| .22 | .18 -----------------------+----------+--------+------+--------+-------- Peroxid of Iron (Fe₂O₃)| 5.18 | 2.39 | 4.80| 3.71 | 6.29 Alumina (Al₂O₃) | 5.57 | 4.51 | 6.28| 5.08 | 7.10 Phosphoric acid (P₂O₅) | .08 | .08 | .07| .09 | .26 Sulfuric acid (SO₃) | .08 | .02 | .06| .10 | .11 Carbonic acid (CO₂) | | | | | -----------------------+----------+--------+------+--------+-------- Water and organic | | | | | matter | 5.50 | 3.11 | 4.20| 5.15 | 6.60 -----------------------+----------+--------+------+--------+-------- Total |99.77 |100.32 |100.88|100.23 |99.54 -----------------------+----------+--------+------+--------+-------- Humus | | | | | “ Ash | | | | | | | | | | Hygroscopic Moisture | 7.29 | 4.08 | 6.84| 4.50 | 8.71 absorbed at °C | 22°C | | | | 18°C -----------------------+----------+--------+------+--------+-------- SHORT-LEAVED PINE. -----------------------+--------+---------+-----------------+--------- State. | North | South | Mississippi |Louisiana |Carolina|Carolina | | -----------------------+--------+---------+--------+--------+--------- County. |Cabarrus|Spartan- | Sumner |Franklin|Morehouse | | burgh | | | -----------------------+--------+---------+--------+--------+--------- Number of Sample. | 9 | 5 | 142 | 71 | 232 -----------------------+--------+---------+--------+--------+--------- ANALYSIS OF FINE EARTH.| | | | | | | | | | Insoluble matter |78.79 | 43.74 |90.23 |88.75 |81.70 | 86.19| 49.61| 92.55| 90.56| 87.45 Soluble silica | 7.40 | 5.87 | 2.32 | 1.81 | 5.75 Potash (K₂O) | .13 | .21 | .24 | .14 | .44 Soda (Na₂O) | .01 | .09 | .09 | .09 | .27 Lime (CaO) | .34 | .03 | .09 | .07 | .10 Magnesia (MgO) | .31 | .21 | .20 | .19 | .24 -----------------------+--------+---------+--------+--------+-------- Bro. ox. of Manganese | | | | | (Mn₃O₄) | .05 | .01 | .07 | .08 | .39 -----------------------+--------+---------+--------+--------+-------- Peroxid of Iron (Fe₂O₃)| 4.99 | 11.70 | 1.84 | 2.41 | 3.55 Alumina (Al₂O₃) | 4.02 | 26.54 | 1.86 | 2.20 | 4.87 Phosphoric acid (P₂O₅) | .14 | .13 | .09 | .08 | .10 Sulfuric acid (SO₃) | .08 | .01 | .01 | .01 | .08 Carbonic acid (CO₂) | | | | | -----------------------+--------+---------+--------+--------+-------- Water and organic | | | | | matter | 3.88 | 11.60 | 2.83 | 4.31 | 2.54 -----------------------+--------+---------+--------+--------+-------- Total | 100.14 |100.22 | 99.87 | 100.14 |100.03 -----------------------+--------+---------+--------+--------+-------- Humus | | | | | “ Ash | | | | | | | | | | Hygroscopic Moisture | 3.65 | 11.21 | 3.57 | 4.4 | 5.47 absorbed at °C | 21.8°C | 21.8°C | 21.8°C | | -----------------------+--------+---------+--------+--------+--------

UPLAND SOILS OF ARID REGION.

======================+============================================ | CALIFORNIA. +----------+---------+------------+---------- |Placer Co.|San Diego| Ventura Co.|Riverside | Auburn. | Co. | | Co. | |National | |Arlington. | | City. | | ----------------------+----------+---------+------------+---------- Number of Sample. | 51 | 47 | 182 | 1406 ----------------------+----------+---------+------------+---------- ANALYSIS OF FINE EARTH.| | | | ----------------------+----------+---------+------------+---------- Insoluble matter | | | 74.91 | 76.41 | 69.52 | 86.21 | 82.84 | 84.61 Soluble silica | | | 7.93 | 8.20 ----------------------+----------+---------+------------+---------- Potash (K₂O) | .38 | .48 | .62 | .87 Soda (Na₂O) | .07 | .14 | .16 | .29 Lime (CaO) | .96 | .36 | .95 | 1.57 Magnesia (MgO) | 1.09 | .54 | .96 | 1.33 ----------------------+----------+---------+------------+---------- Br. ox. of Manganese | | | | (Mn₃O₄) | .39 | .10 | .04 | .04 ----------------------+----------+---------+------------+---------- Peroxid of Iron(Fe₂O₃)| 12.42 | 3.69 | 5.07 | 4.20 Alumina (Al₂O₃) | 10.97 | 5.12 | 5.94 | 5.30 Phosphoric acid (P₂O₅)| .16 | .23 | .13 | .14 Sulfuric acid (SO₃) | .01 | .03 | .04 | .01 Carbonic acid (CO₂) | | | | ----------------------+----------+---------+------------+---------- Water and organic | 5.14 | 2.60 | 2.67 | 1.60 matter | | | | ----------------------+----------+---------+------------+---------- Total | 101.10 | 99.50 | 99.41 | 100.05 ----------------------+----------+---------+------------+---------- Humus | 1.14 | .56 | 1.06 | .20 “ Ash | 1.12 | 1.04 | 1.00 | .64 Hygroscopic Moisture | | 2.30 | 6.59 | 1.77 absorbed at °C | | 15 | 15 | 15 ----------------------+----------+---------+------------+---------- ======================+=======================++================== | WASHINGTON. || MONTANA. +---------+-------------++---------+-------- | Bunch | Bunch grass || Judith | Near | grass |Selah Valley,|| Gap. | Bozeman |Ritzville| Rolling || | Allen’s | Ridge. | Upland. || | Ranch. ----------------------+---------+-------------++---------+-------- Number of Sample. | 46 | 37 || 371 | 387 ----------------------+---------+-------------++---------+-------- ANALYSIS OF FINE EARTH.| | || | ----------------------+---------+-------------++---------+-------- Insoluble matter |76.71 | 77.18 || 74.17 |67.28 | 82.00 | 81.69 || 78.80| 73.83 Soluble silica | 5.28 | 4.59 || 4.61 | 6.54 ----------------------+---------+-------------++---------+-------- Potash (K₂O) | .72 | .62 || 1.07 |1.20 Soda (Na₂O) | .09 | .24 || .16 | .21 Lime (CaO) | 1.04 | 1.32 || .71 | 2.92 Magnesia (MgO) | .94 | .92 || 1.16 | 1.44 ----------------------+---------+-------------++---------+-------- Br. ox. of Manganese | | || | (Mn₃O₄) | .05 | .05 || .97 | .62 ----------------------+---------+-------------++---------+-------- Peroxid of Iron(Fe₂O₃)| 5.14 | 5.62 || 4.20 | 4.63 Alumina (Al₂O₃) | 5.74 | 5.24 || 7.08 | 8.09 Phosphoric acid (P₂O₅)| .16 | .13 || .12 | .18 Sulfuric acid (SO₃) | .01 | .05 || .02 | .01 Carbonic acid (CO₂) | | || 1.76 | ----------------------+---------+-------------++---------+-------- Water and organic | | || | matter | 4.58 | 3.52 || 6.54 | 5.37 ----------------------+---------+-------------++---------+-------- Total |100.48 | 99.37 || 99.94 | 99.69 ----------------------+---------+-------------++---------+-------- Humus | .90 | .48 || | “ Ash | .42 | .32 || | Hygroscopic Moisture | 5.60 | 4.84 || 9.77 |10.37 absorbed at °C | 15 | 15 || 15 | 15 ----------------------+---------+-------------++---------+--------

Soils of the Humid Region.—Taking a view, first, of the table showing the soils of the humid region, it appears that the change of vegetation from walnut and hickory to the short-leaved pine bears no visible relation to the increase or decrease of potash or phosphoric acid, but is plainly governed mainly by the amount of lime present. Where the short-leaved pine prevails the soil is almost always either neutral or shows the alkaline reaction in the course of half an hour; but where the long-leaved pine predominates the soil has almost always an acid reaction. The latter is also usually found in bottoms in which the loblolly pine (P. taeda) prevails, and where, although the soil may show a fair proportion of lime in the analysis, it does not exist in the form of carbonate.

The examples here given are from lands not derived from, or underlaid by, limestone formations. Where the latter exist the percentage of lime is usually materially increased; as it is also in the lowlands or bottoms when compared with adjacent uplands (see above, chapter 10, p. 162; chapter 18, p. 331); as well as in the delta lands of rivers.

Soils of the Arid Region.—Even a cursory comparison of the soils of the arid regions of the Pacific slope with those of the humid, as given in the above tables, shows some striking points of difference. The most obvious is the uniformly high percentage of lime, and usually also of magnesia, in the arid soils, and that quite independently of underlying formations, calcareous or otherwise. This occurs despite the fact that while limestone formations are very prevalent east of the Rocky Mountains, they are quite scarce west of the same. The red (Laramie) sandstones of Wyoming, the slates of the foothills of the Sierra Nevada, the clay shales, granites and eruptives of the Coast Ranges of California, Oregon and Washington, and the varied black rocks of the great lava sheet of the Pacific Northwest, all alike produce soils of high lime content as compared with Eastern soils not derived from calcareous formations. This fact has already been referred to, but is more fully illustrated in the table below.

Aside from the lime-content, however, it will be noted in the preceding table that the potash-content of the arid soils is on the average considerably higher than in those of the humid region. In fact it is hard to find west of the Rocky Mountains (except where high elevation causes a humid climate) any soils as poor in potash as are many of the commonly cultivated lands of the Eastern United States.

Other ingredients do not show such marked differences from the purely chemical standpoint: yet, as will be shown below, the forms in which silica and alumina occur are also not inconsiderably modified.

GENERAL COMPARISON OF SOILS FROM THE ARID AND HUMID REGIONS OF THE UNITED STATES.—In order to verify the conclusions just mentioned upon the broadest basis possible, the following table has been compiled from all available sources; partly published, partly in manuscript only, having remained in the writer’s hands since the cessation of the Northern Transcontinental Survey, prosecuted from 1880 to 1883, under the auspices of the Northern Pacific Railroad, in Washington and Montana. The published data are derived partly from the records of State surveys, partly from the soil work connected with the Tenth Census; partly also from those of Experiment Stations. In most cases it has of course been necessary to restrict the comparison to such analyses as have been made by substantially identical methods, for reasons already given; but in the cases of some states from which numerous analyses made by the Kedzie method, adopted by the Association of Official Chemists, were available, the average has been given but the name of the state starred, to indicate that the percentages, excepting phosphoric acid, are lower than they would be if made by the method adopted by the writer, particularly as regards potash. The adoption of the one-millimeter mesh for the fine-earth sieve instead of the half-millimeter size also creates an unfortunate and ineliminable discrepancy.

Abstracted and revised from Bulletin No. 3, U. S. Weather Bureau, 1893.

In order to exhibit clearly the influence of climate as distinct from other local conditions, it was also necessary to eliminate, in both the arid and humid regions, the soils directly derived from, or connected with calcareous formations; such as the prairies of the Southwestern States, the Bluegrass region of Kentucky, etc. This rule having been applied impartially to the soils of both climatic regions, it can hardly be questioned that the conclusions flowing from a discussion of the results of the comparison are entitled to as much weight as are those of any comparison based on large numbers of observations made, not with reference to the special point under consideration, but with a practical object of which the governing conditions were more or less uncertain, and required to be ascertained by a process of elimination.

The table gives, first, the averages for each ingredient for each of the states represented, the number of analyses from which the averages are derived being given in each case. These averages are given separately for the states of the humid and the arid regions respectively; and at the base of each group the grand average is shown in two forms. The first gives the figures as derived from the aggregate number of soil analyses in each great group, being 696 for the humid, 178 for the transition region and 573 for the arid, divided into the totals resulting from the summation of each ingredient for the whole 696, 178 and 573, respectively.

The second form is that in which the soils of each state are considered as representative of the general character of such state, as the result of intentional selection; such as actually occurred in the cases of those included in the census work of 1880. The figures given here are therefore the result of a summation of the state averages as such, and of their division by the number of states represented.

It will be noted that while these two modes of presentation do change the figures a little, yet in either form the same general result is outlined with striking accuracy. It is also notable that notwithstanding the less complete extraction of soil-ingredients in the starred (★)states, the general ratios between arid and humid soils remain substantially the same. For Western Oregon, local calcareous formations compel omission of three lime figures from the averages.

AVERAGE COMPARISON OF SOILS IN THE HUMID AND ARID REGIONS OF THE UNITED STATES. (A) = Number analyzed. (B) = Insoluble Residue. (C) = Soluble Silica. (D) = Sum of Insoluble Residue and Soluble Silica. (E) = Potash (F) = Soda. (G) = Lime. (H) = Magnesia. ===========================+===+=====+=====+=====+===+====+====+==== | | | | | | | | |(A)| (B) | (C) | (D) |(E)| (F)| (G)| (H) | | | | | | | | ---------------------------+---+-----+-----+-----+---+----+----+---- | | | | | | | | HUMID REGION. | | | | | | | | | | | | | | | | Rhode Island ★ | 7|82.41| 1.69|84.10|.15| .09| .43| .27 North Carolina | 20|81.63| 3.50|85.13|.15| .06| .09| .08 South Carolina | 30|85.54| 3.39|88.93|.12| .07| .07| .12 Georgia | 40|86.07| 2.89|88.96|.15| .07| .08| .10 Florida | 10|85.33| 1.33|86.66|.07| .03| .09| .03 Alabama | 50|81.58| 4.89|86.47|.23| .07| .17| .21 Mississippi | 97|85.87| 4.39|90.26|.28| .11| .15| .31 Louisiana | 35|81.12| 3.54|84.66|.19| .09| .16| .23 Arkansas | 38| | |88.54|.17| .06| .08| .43 Kentucky |185| | |86.72|.20| .10| .08| .19 Ohio ★ |140| | |87.00|.26| .35| .28| .44 | | | | | | | | Oregon (W. of Cascades) | 44|64.82| 5.38|70.20|.23| .19| .83| .73 Average for Humid Region |696|84.17| 4.04|88.21|.21| .14| .13| .29 “ by States | |81.59| 3.45|85.04|.18| .11| .11| .26 | | | | | | | | TRANSITION REGION. | | | | | | | | | | | | | | | | Minnesota. ★--Semi-humid |144|76.60| 8.74|85.34|.30| .23| .65| .43 North Dakota. ★--Semi-arid| 34|68.44| 7.28|75.72|.42| .73| .91| .64 Average for region |178|75.04| 8.46|83.50|.33| .32| .70| .47 | | | | | | | | ARID REGION. | | | | | | | | | | | | | | | | Montana | 59|70.98| 4.17|75.15|.87| .27|1.03|1.36 Idaho | 17|75.34| 5.22|80.56|.56| .26| .85|1.11 Wyoming ★ | 23|76.86| 2.25|79.11|.64| .41|1.91|1.31 Colorado ★ | 16|77.70| 7.10|84.80|.44| .44|1.43| .81 Utah ★ | 38| | |81.04|.98| .53|1.77| .73 Arizona | 20|64.58|13.78|78.36|.82| .43|2.37|1.89 Nevada ★ | 22|71.77| 5.95|77.72|.54| .93|2.04| .96 California |262|66.28| 9.79|76.07|.61| .29|1.25|1.50 ---------------------------+---+-----+-----+-----+---+----+----+---- Oregon East of | 7|72.10| 9.68|81.78|.54| .26|1.23| .73 Washington Cascades |109|71.60| 6.09|77.69|.65| .36|1.25| .96 ---------------------------+---+-----+-----+-----+---+----+----+---- Averages for Arid Region |573|69.16| 6.71|75.87|.67| .35|1.43|1.27 “ by States | |71.91| 7.11|79.02|.67| .42|1.61|1.14 ---------------------------+---+-----+-----+-----+---+----+----+----

(I) = Br. oxide Manganese. (J) = Peroxid of Iron. (K) = Alumina. (L) = Phosphoric Acid. (M) = Sulfuric Acid. (N) = Water and Organic Matter. (O) = Hygroscopic Moisture. (P) = Humus. (Q) = Nitrogen in Humus. (R) = Nitrogen in Soil. ===========================+===+====+====+===+===+=====+====+====+=====+=== | | | | | | | | | | |(I)| (J)| (K)|(L)|(M)| (N) | (O)|(P )| (Q) |(R) | | | | | | | | | | ---------------------------+---+----+----+---+---+-----+----+----+-----+--- | | | | | | | | | | HUMID REGION. | | | | | | | | | | | | | | | | | | | | Rhode Island ★ |.04|3.59|3.66|.09|.10| 7.43|5.23|2.59| | North Carolina |.07|4.72|5.71|.12|.06| 3.98|4.18| | | South Carolina |.05|2.47|4.59|.11|.06| 3.39|4.22| .42| | Georgia |.09|2.75|4.02|.11|.10| 3.62|3.54| | | Florida |.08| .60|1.17|.08|.05| 1.89|1.72| | | Alabama |.12|3.81|2.70|.13|.05| 4.04|7.07| | | Mississippi |.14|2.64|4.07|.09|.03| 3.33|5.41| | | Louisiana |.02|3.12|4.24|.10|.05| 4.26|6.66| | | Arkansas |.21|3.10|3.51|.15|.05| 3.70|2.47| | | Kentucky |.20|6.01|3.52|.11|.04| 3.69|1.85| | | Ohio ★ | |3.11|3.36|.11|.04| 5.04| | | | Oregon (W. of Cascades) |.09| 11.64 |.23|.16| 3.20| |1.55| | Average for Humid Region |.13|3.88|3.66|.12|.05| 4.40| |1.22| | “ by States |.10|3.26|3.68|.12|.06| 3.96| |1.52| | | | | | | | | | | | TRANSITION REGION. | | | | | | | | | | | | | | | | | | | | Minnesota. ★--Semi-humid | |2.83|4.43|.22|.01| 7.30| |2.91| 6.53|.19 North Dakota. ★--Semi-arid| |3.62|5.17|.19|.05|13.85| |4.67| 7.28|.34 Average for region | |2.08|4.57|.21|.02| 8.55| |3.24| 6.67|.22 | | | | | | | | | | ARID REGION. | | | | | | | | | | | | | | | | | | | | Montana |.37|4.28|6.81|.22|.06| |7.14| | | Idaho |.02|3.85|6.38|.16| | 5.01|2.00|1.68| 5.95|.10 Wyoming ★ | |3.05|6.61|.18|.11| 5.48| | | | Colorado ★ | |3.82|4.98|.23|.03| 3.57|2.31| | |.03 Utah ★ |.03|3.08|5.50|.22| | 6.27|2.37| | | Arizona |.06|4.92|6.43|.13|.06| 3.57| |1.65| | Nevada ★ |.32|5.67|5.00|.32|.14| 5.93| | | |.12 California |.06|6.61|8.44|.10|.06| 4.74|6.09|0.91|15.23|.14 Oregon } East of |.08| 10.75 |.11|tr.| 4.40| | .67| | Washington } Cascades | |5.37|6.31|.21|.03| 5.77|5.14| | | Averages for Arid Region |.11|5.48|7.21|.16|.06| 5.15|5.46|1.13|12.50|.13 “ by States |.13|4.74|6.27|.19|.07| 4.71|5.34|1.03|10.59|.10 ---------------------------+---+----+----+---+---+-----+----+----+-----+---

New Mexico.—Few analyses of New Mexico soils have been made, but the average results of six partial determinations made by Goss, and one full analysis made by Hare according to the method of the writer, and given below, show substantial accord with the averages of the above table. The averages of Goss’ determinations are: Potash .780, Phosphoric acid .221, Nitrogen .108 per cent.

CHEMICAL ANALYSIS OF RIO GRANDE SILT (by Prof. R. F. Hare.)

Deposited on land by irrigation.

Insoluble matter 63.70 Potash (K₂O) 1.06 Soda (Na₂O) .22 Lime (CaO) 4.97 Magnesia (MgO) 2.43 Br. ox. of Manganese (Mn₃O₄) .14 Peroxid of Iron (Fe₂O₃) 5.80 Alumina (Al₂O₃) 6.86 Phosphoric acid (P₃O₅) .16 Sulfuric acid (SO₃) .13 Carbonic acid (CO₂) 7.45 Water and organic matter 9.98

Humus 1.17 “ Nitrogen 11.11 “ “ per cent. in soil .13

Hygroscopic Moisture absorbed at °C 2.63

DISCUSSION OF THE TABLE.

Lime.—Considering in this table, first, lime, a glance at the columns for the two regions shows a surprising and evidently intrinsic and material difference, approximating in the average by totals to the proportion of 1 to 11; in the average by states, 1 to 14½. This difference is so great that no accidental errors in the selection or analysis of the soils can to any material degree weaken the overwhelming proof of the correctness of the inference drawn upon theoretical grounds, viz., that the soils of the arid regions must be richer in lime than those of the humid countries. For the differences in derivation would, in view of the wide prevalence of limestone formations in the humid regions concerned, produce exactly the reverse condition of things from that which is actually found to exist; and if further proof were needed it can readily be found in the detailed discussion of the analyses of the soils of the arid areas forming the contrast. This shows that for instance, in Washington highly calcareous soils are directly derived from the black basaltic rocks; while similarly, calcareous lands are found in California to be the outcome of the decomposition of granites, diorites, lavas, clay-shales and sandstones.

It is not easy to overrate the importance of this feature of the soils of the arid region, as it is intimately connected with other theoretically and practically important facts, in part already mentioned.

Summary of Effects of Lime Carbonate in Soils.—It is best to summarize, briefly, at this point, the advantages (and possible disadvantages), resulting from the presence of a proper amount of lime carbonate in soils, so far as these are at present understood.

Physically, even a small amount of lime carbonate, by its solubility in the carbonated soil-water, will act most beneficially in causing the flocculation of clay and in the subsequent conservation of the flocculent or tilth condition, by acting as a light cement holding the soil-crumbs together when the capillary water has evaporated; thus favoring the penetration of both water and air, and of the roots themselves. It should be added that according to the experience of the writer, amounts of lime carbonate in excess of 2% do not add to the favorable effects, except as would so much sand.

As to chemical effects, among the most important are:—

1. The maintenance of the neutrality of the soil, by the neutralization of acids formed by the decay of organic matter, or otherwise.

2. The maintenance, in connection with the proper degrees of moisture and warmth, of the conditions of abundant bacterial life (see above,