Soils and fertilizers . s are very small, we find a relatively large propor-tion of them in a clay soil, but a very small proportion ina sand. Another operation that accompanies soil formation isthe incorporation of vegetable matter or animal remains —together called organic matter — with the soil adds greatly to the crop-producing power of a soil,for as the organic matter decays it makes more solublethe inorganic constituents. QUESTIONS 1. Name the agencies concerned in soil formation and trans-portation. 2. In what way do heat and cold act to decompose rock ? 3. What is the ac
Soils and fertilizers . s are very small, we find a relatively large propor-tion of them in a clay soil, but a very small proportion ina sand. Another operation that accompanies soil formation isthe incorporation of vegetable matter or animal remains —together called organic matter — with the soil adds greatly to the crop-producing power of a soil,for as the organic matter decays it makes more solublethe inorganic constituents. QUESTIONS 1. Name the agencies concerned in soil formation and trans-portation. 2. In what way do heat and cold act to decompose rock ? 3. What is the action of frost on rock ? 4. How does water aid in the transportation of soil ? 5. What part did the great glaciers play in soil formation ? 6. Has wind been more potent as a soU former or as a trans-porter ? 7. Describe the ways in which roots aid in the decompositionof rocks. 8. Explain the difference between powdered rock and soil. S^^p ^^^M uni ^^H^^K^^Bu^Sff^V^ ^^Si if*^^^^ jf^k^ * jTO^j **?-?-*-v^ ; *? Sbl. Plate IV. Plants as Soil Formers. — Plants are active agents inthe decomposition of rock. In the upper figure lichens may be seenbeginning the disintegration, and in the lower, large tree roots are forcingthemselves into the cracks in the rock. SOIL FORMATION AND TRANSPORTATION. 17 LABORATORY EXERCISES Exercise I. — Soil formation and transportation. This exercise is based on observations in the field and its valuedepends on examples available. Use Chapter II as a basis for thefield observations. If rock outcrops can be found in the neighborhood, a visit to themwould be worth while. Examples of wind action, heat and cold,frost, and plant and animal influences in forming or transporting soilshould easily be found. The erosive and carrying power of streamsshould also be studied in relation to soil formation. An examination of weathered rock of various kinds should bemade in order to illustrate the chemical phase of soil rusting of iron could be used a
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