FACTORS OF SOIL FORMATION - Midlands State University

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criteria may stand in contradistinction to each other. Theoretically, at least, soils may be in equilibrium with the environment without having marked profile features, and, vice versa, soils may have welldeveloped profiles without being in equilibrium. The foregoing discussions represent but a fragmentary analysis of the nature of soil maturity. It has been the purpose to elucidate this cardinal concept of modern pedology rather than to pass dogmatic judgment on its practical utility. Time as an Element in Soil Classification.—Most systems of soil classification contain, in some form or another, the idea of soilforming factors. Among these, the factor time or the degree of maturity occupies the most prominent role. Shaw (17) has proposed special names for the several degrees of maturity: Solum crudum (raw soil), Solum semicrudum (young soil, only slightly weathered), Solum immaturum (immature soil, only moderately weathered), Solum semimaturum (semimature, already considerably weathered), Solum maturum (mature soil, fully weathered). A consistent classification of soils according to degrees of maturity is obtained for conditions of constancy of climate, organisms, parent material, and topography. In accordance with Eq. (7) the soil profile then becomes solely a function of time. Shaw's San Joaquin family of soils in California provides a good illustration. This FIG. 27.—Percentage of inorganic colloidal material of the San Joaquin family as a function of depth. soil family has developed on broad alluvial fans composed of granitic rock debris. The climate is semiarid with a rainfall ranging between 10 and 20 in. The native cover is shrubs, herbs, and grass with occasional oak trees. Shaw divides the sequence of development states into six phases
Tujunga sand —> Hanford fine sand —> Greenfield sand —> Ramona sandy loam —> Placentia sandy loam —> San Joaquin sandy loam Tujunga is the youngest member, with the least developed soil profile; San Joaquin represents the climax, the mature soil. Soil reaction varies little throughout the soil-forming process; it fluctuates between pH 7.2 and 8.2. The most outstanding feature is the colloid content, particularly its distribution among the various horizons of the profile (Fig. 27). In the A horizon, the colloid content increases from 0.83 per cent in the Tujunga to 7 per cent in the older members. The most drastic changes occur in the B horizon where, in the advanced stages, the clay accumulation gives rise to a reddish, indurated, impervious hardpan. The factor time or age also figures prominently in the current system of classification of soils of the United <strong>State</strong>s, which is an offspring of the Russian school of thought. Kellogg (3) and his associates classify all soils into three great orders: zonal soils, intrazonal soils, and azonal soils. The last two orders contain, among other soil types, those soils that, owing to their youth, have not fully developed profiles. Marbut's system of soil classification also includes the time factor. His differentiation of soils into pedocals and pedalfers (see page 190) applies only to soils that have mature profiles. Notwithstanding the great popularity of systems of classification based on maturity series, we should not lose sight of their speculative and hypothetical nature. At present we have no reliable method of determining accurately the degree of maturity of any soil type. Literature Cited 1. AALTONEN, V. T.: Zur Stratigraphie des Podsolprofils, II, Commun. Instituti Forestalls Fenniae, 27.4 : 1-133, Helsinki, 1939. 2. AKIMTZEV, V. V.: Historical Soils of the Kamenetz-Podolsk Fortress, Proc. Second Intern. Congr. Soil Sci., 5 : 132-140, 1932. 3. BALDWIN, M., KELLOGG, C. E., and THORP, J.: Soil Classification, Yearbook of Agriculture, 1938: 979-1001, U. S. Government Printing Office, Washington, D. C. 4. BISSINGEB, L.: Uber Verwitterungs-Vorgänge, Dissertation, Erlangen, 1894. 5. GEIKIE: Rockweathering, as illustrated in Edinburgh churchyards, Proc. Roy. Soc. Edinburgh, 10 : 518-532, 1880. 6. GOODCHILD, J. G.: Notes on some observed rates of weathering of limestones, Geol. Mag., 27 : 463-466, 1890. 7. HARDY, P.: Soil erosion in St. Vincent, B.W.I., Trop. Agr. (Trinidad), 16 : 58-65, 1939. 8. HILGER, A.: Über Verwitterungsvorgänge bei krystallinischen und Sedimentärgesteinen, Landw. Jahrb., 8 : 1-11, 1897. 9. HILGER, A., and SCHÜTZE, R.: Über Verwitterungsvorgänge bei krystallinischen und Sedimentärgesteinen, II, Landw. Jahrb., 15 : 432- 451, 1886. 10 HIRSCHWALD, J.: "Die Prüfüng der natürlichen Bausteine auf ihre Wetterbeständigkeit," Berlin, 1908. 11. HISSINK, D. J.: The reclamation of the Dutch saline soils (Solonchak) and their further weathering under humid climatic conditions of Holland, Soil Sri., 45 : 83-94, 1938. 12. M ARBUT, C. F.: Soils of the United <strong>State</strong>s, Atlas of American Agriculture, Part III, U. S. Government Printing Office, Washington, D. C, 1935. 13. MATTSON, S., and LÖNNEMARK, H.: The pedography of hydrologic podsol series I, Ann. Agr. Coll. Sweden, 7 : 185-227, 1939. 14. MERRILL, G. P.: "Stones for Building and Decoration," New York, 1903. 15. SALISBURY, E. J.: Note on the edaphic succession in some dune soils with special reference to the time factor, J. Ecol, 13 : 322-328, 1925.
Page 1 and 2: FACTORS OF SOIL FORMATION A System
Page 3 and 4: To MY WIFE
Page 5 and 6: PREFACE The College of Agriculture
Page 7 and 8: FACTORS OF SOIL FORMATION CHAPTER I
Page 9 and 10: To a certain extent, many geologica
Page 11 and 12: FIG. 6.—Illustration of a soil in
Page 13 and 14: FIG. 8.—The larger system. (After
Page 15 and 16: However, it remained for Hilgard in
Page 17 and 18: These terms are identical with the
Page 19 and 20: thus avoid lengthy excursions into
Page 21 and 22: CHAPTER II METHODS OF PRESENTATION
Page 23 and 24: Colloid chemists favor size-distrib
Page 25 and 26: These ratios afford a means of dete
Page 27 and 28: FIG. 14.—Illustration of soil var
Page 29 and 30: Studies on Experimental Weathering.
Page 31 and 32: een very rapid, an average thicknes
Page 33 and 34: FIG. 18.—This graph shows in a sk
Page 35 and 36: thickness of the eluvial horizon in
Page 37 and 38: material contained from 9 to 10 per
Page 39: FIG. 25.—Schematic illustration o
Page 43 and 44: CHAPTER IV PARENT MATERIAL AS A SOI
Page 45 and 46: they would have to be considered as
Page 48 and 49: Physical and Chemical Rock Decay.
Page 50 and 51: FIG. 31.—Comparison of relative b
Page 52 and 53: environment should produce soils th
Page 54 and 55: TABLE 13.—RELATIVE PERCOLATION VE
Page 56 and 57: In certain parts of the world, espe
Page 58 and 59: minds of all students of loessial s
Page 60 and 61: that parent material is one of the
Page 62 and 63: Jersey, out of 48 soil types, 24, o
Page 64 and 65: Scherf claims that the climate of t
Page 66 and 67: 13. KAY, G. F., and APPEL, E. T.: T
Page 68 and 69: FIG. 42.—Relationship between slo
Page 70 and 71: Specific examples of the relationsh
Page 72 and 73: FIG. 46.—Distribution of organic
Page 74 and 75: suffered salinization. Some of the
Page 76 and 77: from Marbut's standpoint; but, in t
Page 78 and 79: FIG. 50.—Distribution of mean ann
Page 80 and 81: main, they have not been very succe
Page 82 and 83: modifications in environment due to
Page 84 and 85: correlation exists between total so
Page 86 and 87: FIG. 59.—Soil nitrogen-depth func
Page 88 and 89: eliminates chance correlation. More
Page 90 and 91:
TABLE 25.—CHEMICAL EVIDENCE OF TH
Page 92 and 93:
(49), and thereby identify the soil
Page 94 and 95:
FIG. 65.—Relationship between CaO
Page 96 and 97:
published in the Soil Survey Report
Page 98 and 99:
(usually pH 7) is known as the base
Page 100 and 101:
In Table 30 are given corresponding
Page 102 and 103:
particularly in the more humid regi
Page 104 and 105:
The hydrogen ion concentration and
Page 106 and 107:
Soil Color.—In humid regions of t
Page 108 and 109:
Nitrogen and Organic Matter as a Fu
Page 110 and 111:
area by soil scientists of the U. S
Page 112 and 113:
TABLE 38.—DATA FOR THE PARENT MAT
Page 114 and 115:
Crowther correlates clay compositio
Page 116 and 117:
Podsols.—In vast areas of norther
Page 118 and 119:
FIG. 85.—Diagrammatic section of
Page 120 and 121:
FIG. 87.—Comparison of podsolizat
Page 122 and 123:
ft. above sea level, the total nitr
Page 124 and 125:
Generalized Soil-climate Functions.
Page 126 and 127:
d. Under conditions of constant moi
Page 128 and 129:
horizons. The decrease in the clay
Page 130 and 131:
directly from the melting ice. Thic
Page 132 and 133:
FIG. 97.—Climatic and vegetationa
Page 134 and 135:
soil processes occur mainly during
Page 136 and 137:
FIG. 98.—Chernozem soil near Khar
Page 138 and 139:
FIG. 99.—Marbut's classification
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47. MARBUT, C. F.: A scheme for soi
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CHAPTER VII ORGANISMS AS A SOIL-FOR
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as a consequence of natural reinocu
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intensive leaching supports acidoph
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TABLE 51.—AREAS OF NATURAL VEGETA
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TABLE 53.—DRY WEIGHTS OF LIVING U
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TABLE 56.—RAINFALL AND PLANT PROD
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the yields of corn: that is to say,
Page 156 and 157:
disappear and acid-tolerant species
Page 158 and 159:
TABLE 60.—COMPARISON OF PRAIRIE A
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differences are found in the distri
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Here also the leaves of the deciduo
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indeterminate past. The land, after
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chapters, we must be content with a
Page 168 and 169:
Duley (44) initiated the first scie
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matter acts as a binding agent betw
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areas in the San Joaquin Valley of
Page 174 and 175:
independent variables. These latter
Page 176 and 177:
Inherent Productive Capacity of Soi
Page 178 and 179:
FIG. 121.—Showing the relation be
Page 180 and 181:
FIG. 123.—Decline of soil nitroge
Page 182 and 183:
FIG. 124.—This graph depicts the
Page 184 and 185:
25. HOSKING, J. S.: The carbon-nitr
Page 186 and 187:
CHAPTER VIII CONCLUSIONS In this ch
Page 188 and 189:
the other correlates soils in terms
Page 190 and 191:
knowledge of the physical, chemical
show all

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