Soils Honor

Nature Study

Requirements

1. Define what soil means.

   Answer: Soil is the surface layer of the Earth's crust formed by the alteration of rocks (weathering) mixed with organic matter (decomposition of plants and animals), water, air, and living organisms. It is a dynamic, three-dimensional natural system, composed of minerals, gases, liquids, and living beings, capable of supporting plants and regulating water flows. — The scientific definition goes beyond 'dirt'. Soil is alive - it has bacteria, fungi, earthworms, roots. It is finite (1 cm of soil takes 100-1000 years to form). Its loss through erosion is a silent tragedy. The UN declared 2015 the International Year of Soils. In Brazil, soils are varied: clayey, sandy, lateritic, Inceptisols. EMBRAPA Solos conducts research. Christian stewardship of the earth includes caring for the soil. At ecological camporees, workshops show how to create fertile soil by composting.

2. Where on Earth is soil located?

   Answer: Soil is located in the pedosphere, the surface layer of the Earth's crust that covers the continents, with a thickness varying from a few centimeters to several meters (average 1-2 m). It is present in all continental masses, except in extreme rocky deserts, polar glaciers, mountains with exposed rock, and the ocean floor (which has sediments, not soil). — Soil is distributed unevenly. Dense areas: the Argentine pampas, the Brazilian Cerrado, the American plains. Areas without soil: ice mountain ranges, rocky deserts like the Atacama. Depth varies: in the Amazon jungles it can be shallow (5-30 cm) over the water table; on plateaus it can be meters deep. Brazil has diverse soils due to its size. Pedological maps from IBGE/EMBRAPA detail the distribution. At camporees with an agricultural theme, knowing where soil is guides planting. Soil is a finite resource that needs to be preserved.

3. What are the five key factors in soil formation?

   Answer: There are five soil-formation factors: 1) Parent material (the bedrock): the type of rock that undergoes weathering determines the mineralogy and basic composition of the soil. 2) Climate: rainfall (leaches minerals) and temperature (speeds up or slows down chemical reactions) deeply influence the pace of formation. 3) Living organisms: plants, animals, and microorganisms add organic matter, turn over the soil, and aid in decomposition. 4) Relief (topography): the slope and position on the terrain affect drainage, erosion, and water accumulation. 5) Time: the longer the other factors act, the deeper and more developed (with defined horizons) the soil becomes. — The factors were proposed by Hans Jenny in 1941 (CLORPT - climate, organisms, relief, parent material, time). Each combination produces a unique soil. Brazil has great pedological diversity. Humid tropical areas form deep, acidic Oxisols (latossolos). Dry regions form shallow Entisols (neossolos). Slopes have thin soils due to erosion. Flat areas accumulate material. At agricultural camporees, understanding the factors helps in choosing suitable crops. EMBRAPA maps Brazilian soils systematically.

4. Define the following terms:
   • Horizon A
   • Horizon B
   • Horizon C
   • Organic layer
   • Mineral layer
   • Clay
   • Leaching
   • Humus
   • Soil profile
   • Parent material
   • Pedologist

   Answer: 1) A horizon: the surface layer of the soil, dark, rich in humus and organic matter, where roots and the greatest biological activity are concentrated. 2) B horizon: the subsoil, where minerals and clays that have been leached (washed) from the A horizon accumulate; it is usually more compact and a different color. 3) C horizon: a layer of barely altered parent material, formed by partially decomposed bedrock, below the B. 4) Organic layer: the part of the soil (usually at the surface) made up of living and dead organic matter, such as leaves, roots, and decomposing remains of organisms. 5) Mineral layer: the part of the soil dominated by mineral components (sand, silt, and clay) from the decomposition of rocks, with little organic matter. 6) Clay: a very fine mineral particle (smaller than 0.002 mm) that retains water and nutrients well and gives plasticity to the soil. 7) Leaching: the process in which infiltrating water carries nutrients and particles from the upper layers to the deeper ones, impoverishing the surface. 8) Humus: already decomposed and stable organic matter, dark, which improves fertility, water retention, and soil structure. 9) Soil profile: a vertical cut of the soil, from the surface to the bedrock, showing the sequence of horizons (A, B, C, etc.). 10) Parent material: the rock or deposit from which the soil was formed by the action of climate and organisms over time. 11) Pedologist: the scientist who specializes in the study of soils (pedology), analyzing their formation, classification, and characteristics. — Essential pedological vocabulary for soil studies. Horizons A-B-C form the classic profile (some have more subdivisions: O, A, E, B, C, R). Leaching is a critical process in tropical Brazil (rains remove nutrients). Humus is precious (it forms slowly). Clay has a high cation exchange capacity (CEC). The profile is photographed in trenches. Pedologists are specialized professionals (trained in agronomy, geology, geography). At scientific camporees, the soil profile workshop digs a hole for visualization.

5. Define the term "Soil Classification". Why are soils classified?

   Answer: Soil Classification is the system of organization and nomenclature that groups soils by similar physical, chemical, mineralogical, and morphological properties. In Brazil, the Brazilian Soil Classification System (SiBCS) of EMBRAPA is used, with 13 main classes (Oxisols, Ultisols, Entisols, etc.). Soils are classified to: facilitate communication and study (using a common language among technicians); predict soil behavior (fertility, drainage, erosion risk); indicate the most suitable use (which crop to plant, where to build); guide management and conservation; and organize knowledge into soil maps useful for agricultural and environmental planning. — Classifying soils is like classifying plants/animals. Without a system, it would be chaos. SiBCS is the Brazilian version; worldwide, the WRB (FAO) and Soil Taxonomy (USDA) coexist. Each soil has properties that determine its suitability. Oxisols are deep and old; Ultisols have a clayey horizon; Entisols are young. Knowing the class guides crop choice. EMBRAPA Solos publishes the pedological map of Brazil. At camporees with agriculture, knowing the classification guides proper planting.

6. Discuss three differences between the following types of soil:
   • Desert
   • Temperate
   • Tropical

   Answer: Comparison of three differences between desert, temperate, and tropical soils: 1) Moisture/water: desert soil is very dry with minimal leaching; temperate soil has good, balanced water availability; tropical soil receives a lot of rain and suffers strong nutrient leaching. 2) pH/chemistry: desert soil tends to be alkaline (pH 7.5-8.5) with salt accumulation; temperate soil is neutral to slightly acidic (pH 6-7); tropical soil is generally acidic (pH below 5.5) and poor in bases. 3) Organic matter/fertility: desert soil has little organic matter and sparse vegetation; temperate soil accumulates a lot of organic matter under dense vegetation, being very fertile (e.g., prairie Mollisols); tropical soil, despite its lush vegetation, has organic matter that decomposes quickly and deep but leached and less fertile soils (e.g., Oxisols). — Climate determines soil. Brazil is predominantly tropical (Amazon, Cerrado, Caatinga). Brazilian tropical soils are deep but poor in nutrients - liming is necessary. Argentina and Uruguay (the pampas) have rich temperate soils. North Africa and the U.S. Southwest have deserts. Each type requires its own agricultural management. At scientific camporees, workshops compare samples of different soils. Knowing the differences guides sustainable agriculture and conservation. Brazilian soils are unique due to the extreme tropicality of their formation.

7. Examine a 60 cm vertical section of soil. Label the different types of organic matter found, identify the different soil horizons, and mark the transition between the soil layer and the mineral layer.

   Answer: Dig a trench 60 cm deep and mark each horizon (A, dark with humus; B, lighter, accumulating minerals; C, with fragments of bedrock). Identify the decomposed organic matter at the top and mark the transition between the organic and mineral layers. — The 60 cm profile generally reveals horizons A, B, and the beginning of C. The organic layer (decomposing leaves) is in the first centimeters. The transition is visible by color (dark→light) and texture. Tools: shovel, knife, tape measure, field notebook. EMBRAPA has detailed manuals.

8. Draw, photograph, or collect and correctly label five different types of soil.

   Answer: Visit various locations and collect: 1) clayey (reddish, plastic when moist); 2) sandy (light, granular); 3) silty (silky to the touch); 4) humic (dark, organic); 5) calcareous (grayish-white). Label each sample with the location, date, and visible characteristics for comparison. — Each type has unique drainage and fertility properties. Clayey soil retains water; sandy soil drains quickly. Plastic containers can be used for storage. Brazil has enormous pedological diversity - red Oxisols, quartzarenic Entisols, Vertisols. EMBRAPA has a national pedological map available.