SOIL SCIE N CE eo this term is based on the upper limit of s flashcards

All 12 cards

1. Card 1

   Define 'soil' according to the provided source material.

   Soil is a mixture of organic and inorganic materials that developed on the earth's surface through the weathering process of rocks and minerals. Its properties are conditioned by climate, living organisms, and topography acting on parent material over time. It serves as a medium for plant growth by providing physical support, water, and nutrients.

2. Card 2

   Explain the difference between the pedological and edaphological approaches to studying soil.

   The pedological approach studies soils with a primary interest in characterizing and differentiating their properties, with minor emphasis on practical use, such as taxonomic classification. In contrast, the edaphological approach emphasizes the practical use of soils, particularly the relationship of soil properties to plant growth, as seen in studies of soil fertility or productivity.

3. Card 3

   What are the two main components of soil solids and their respective typical percentages?

   The two main components of soil solids are mineral matter, which typically constitutes 45%, and organic matter, which typically makes up 5%. Mineral matter comes from weathered rocks and minerals, while organic matter is derived from decayed plant and animal remains.

4. Card 4

   Describe the characteristics of soil air and its importance for plant roots.

   Soil air occupies the pore spaces of the soil and is largely composed of nitrogen (78%), oxygen (20%), and carbon dioxide (0.5%). It provides oxygen for the respiration of plant roots, and sufficient aeration is crucial for the exchange of CO2 and O2, preventing toxic CO2 buildup.

5. Card 5

   What are igneous rocks, and name two common soil-forming igneous rocks found in the Philippines.

   Igneous rocks are original rocks formed from the solidification of molten magma within or outside the earth's crust at high temperatures. Basalt and andesite are among the dominant soil-forming igneous rocks in the Philippines, contributing to soil series like Adtuyon and Jasaan.

6. Card 6

   Explain the process of illuviation and calcification as soil formation processes.

   Illuviation is the general term for the movement of soil material from one part of the soil to another, resulting in the formation of argillic (clayey) layers. Calcification specifically refers to the transfer and accumulation of calcium carbonate within a particular soil horizon.

7. Card 7

   What is soil texture, and how stable is this property?

   Soil texture refers to the relative proportion of various size fractions: sand, silt, and clay in the soil. It is considered a relatively stable property of the soil, as it is determined by the inorganic components and cannot be altered by adding organic matter. However, it can change if large amounts of these fractions are deposited by flooding or volcanic eruptions.

8. Card 8

   Compare the water holding capacity and aeration of sandy soils versus clayey soils.

   Sandy soils generally have low water holding capacity and very good aeration due to more macropores. Clayey soils, on the other hand, have high water holding capacity due to more micropores but tend to have poor aeration and drainage. Water moves slowly but farther in clayey soils.

9. Card 9

   What is soil moisture tension (SMT), and how does it relate to soil dryness?

   Soil moisture tension (SMT) is the force by which water is held in the soil, representing the force plant roots must overcome to draw water. SMT is low in wet soils and increases as the soil dries up, meaning higher tension indicates less available water.

10. Card 10

    Calculate the percent moisture content by weight (MCw) of a soil sample if its fresh weight (FW) is 150g and its oven-dried weight (ODW) is 120g.

    Using the formula %MCw = [(FW – ODW) / ODW] x 100, the calculation is: %MCw = [(150g - 120g) / 120g] x 100 = (30g / 120g) x 100 = 0.25 x 100 = 25%. Therefore, the moisture content by weight is 25%.

11. Card 11

    Explain the difference between water at Field Capacity (FC) and water at Permanent Wilting Point (PWP).

    Water at Field Capacity (FC) is an estimate of the upper limit of available moisture, occurring when excess water has drained from large pores, leaving water in smaller pores (SMT = 1/3 bar). Water at Permanent Wilting Point (PWP) is an estimate of the lower limit of available moisture, where plants permanently wilt because they can no longer draw water due to very high moisture tension (SMT = 15 bar).

12. Card 12

    What is soil consistency, and how does it affect the workability of soil at different moisture contents?

    Soil consistency describes the physical condition of the soil, manifesting cohesion and adhesion forces at various moisture contents, and indicates its workability. A soil can be hard when dry, friable when moist (ideal for cultivation), sticky and plastic when wet (good for pottery), and viscous when supersaturated.

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