Soil Science Answers PDF

1. What process primarily organizes knowledge about soils and their relationships? A. Soil fertility assessment B. Soil management C. Soil erosion D. Soil classification Answer: Soil classification (D) Soil classification is crucial for organizing knowledge about soils and unde...

1. What process primarily organizes knowledge about soils and their relationships? A. Soil fertility assessment B. Soil management C. Soil erosion D. Soil classification Answer: Soil classification (D) Soil classification is crucial for organizing knowledge about soils and understanding their interrelationships. 2. Which soil order is characterized by high organic matter and is suitable for pasture when conserved? A. Histosol B. Entisol C. Mollisol D. Andisol Answer: Histosol (A) Histosols are known for their high organic matter content, making them fertile and suitable for pasture. 3. What process describes the conversion of inorganic nitrogen into organic nitrogen in soil? A. Nitrification B. Immobilization C. Denitrification D. Ammonification Answer: Immobilization (B) Immobilization is the process where inorganic nitrogen is converted into organic forms by microorganisms. 4. Which of the following describes the soil temperature regime with a mean annual temperature of greater than 22°C? A. Pergelic B. Hyperthermic C. Thermic D. Mesophilic Answer: Hyperthermic (B) The hyperthermic temperature regime is characterized by a mean annual temperature exceeding 22°C. 5. What is the main characteristic of Agrilic soil horizons? A. Rich in organic matter B. Illuvial horizon of clay accumulation C. High content of volcanic ash D. Thin and light-colored Answer: Illuvial horizon of clay accumulation (B) Agrilic horizons are defined by the accumulation of clay, particularly white clay, in the illuvial horizon. 6. Which type of bacteria is primarily responsible for denitrification in soil, converting nitrates back to nitrogen gas? A. Rhizobia B. Nitrosomonas C. Azotobacter D. Pseudomonas Answer: Pseudomonas (D) Pseudomonas are one of the key groups of bacteria involved in denitrification, reducing nitrates to nitrogen gas. 7. What factor most significantly affects the accumulation of soil organic matter (SOM)? A. Topography B. Soil Color C. Soil pH D. Temperature Answer: Temperature (D) Soil organic matter accumulation is influenced primarily by temperature, moisture, texture, and cropping systems. 8. Which type of mycorrhizae primarily penetrates plant root cells? A. Endomycorrhiza B. Ectomycorrhiza C. Arbuscular mycorrhiza D. Vesicular-arbuscular mycorrhiza Answer: Endomycorrhiza (A) Endomycorrhizae penetrate the cells of the host plant, assisting in nutrient absorption. 9. What is the primary role of actinomycetes in soil? A. Attacking and simplifying organic compounds B. Fixing atmospheric nitrogen C. Absorbing water D. Decomposing lignin Answer: Attacking and simplifying organic compounds (A) Actinomycetes serve as intermediates between bacteria and fungi, attacking and simplifying organic materials. 10. Why does organic matter (OM) accumulate more in grasslands compared to forests? A. Faster turnover of vegetative matter B. Longer lifespan of trees C. Higher precipitation levels D. Less microbial activity Answer: Faster turnover of vegetative matter (A) Grasslands have a faster turnover of vegetative matter and shorter grass life cycles that contribute to higher OM accumulation. 11. In the context of composting, what is the typical C/N ratio? A. 14/1 to 20/1 B. 30/1 C. 25/1 D. 10/1 Answer: 14/1 to 20/1 (A) The C/N ratio of finished compost ranges from 14:1 to 20:1 to ensure proper decomposition. 12. What microbial process is responsible for reducing sulfate to sulfide? A. Fermentation B. Sulfur reduction C. Decomposition D. Sulfate oxidation Answer: Sulfur reduction (B) Desulfovibrio and Desulfotomaculum are examples of microbes that can reduce sulfate to sulfide. 13. What contributes to the enhancement of soil organic matter decline during cultivation? A. Enhanced oxidation and microbial activity B. Soil pH reduction C. Decreased soil temperature D. Increased rainfall Answer: Enhanced oxidation and microbial activity (A) Cultivation leads to increased oxidation and microbial activity, contributing to a decline in soil organic matter. 14. Which of the following processes occurs during thermophilic stages of composting? A. Pathogen destruction B. Lignin breakdown C. Nutrient leaching D. Water retention Answer: Pathogen destruction (A) During the thermophilic stage, temperatures reach between 50-75°C, which helps in the destruction of pathogens. 15. Which of the following is a component of soil organic matter (SOM) typically found in the greatest percentage? A. Water-soluble fraction B. Hemicellulose C. Cellulose D. Lignin Answer: Cellulose (C) Cellulose is generally the most abundant component, making up 15-60% of SOM. 16. What is a significant byproduct of microbial sulfur transformation in soils? A. Organic acids B. Nitrogen gas C. Carbon dioxide D. Phosphates Answer: Organic acids (A) Microbial transformations of sulfur lead to the production of various organic acids. 17. Which method can help mitigate iron toxicity in sodic soils? A. Deep plowing B. Apply organic fertilizers regularly C. Use of drought-tolerant crops D. Irrigation and regular drainage Answer: Irrigation and regular drainage (D) Irrigation and drainage help reduce the excess iron under flooded conditions, alleviating toxicity. 18. What is the primary benefit of liming with CaCO3 in acidic soils? A. Increase salinity levels B. Improve soil structure C. Enhance iron toxicity D. Neutralize soil acidity Answer: Neutralize soil acidity (D) Liming with calcium carbonate helps to neutralize the acidity in soils, improving conditions for plant growth. 19. Which of the following statements about soil pore space is correct? A. Micropores retain water for plants B. Macropores significantly limit root growth C. Micropores primarily hold air for aeration D. Macropores hold water for microbial activity Answer: Micropores retain water for plants (A) Micropores are essential for holding water, whereas macropores are crucial for air exchange and root growth. 20. What role do composts play in managing saline soils? A. Increase soluble salt content B. Suppress microbial activity C. Enhance soil fertility D. Increase the pH of the soil Answer: Enhance soil fertility (C) Composts help improve organic matter content and enhance nutrients, thereby helping in managing saline conditions. 21. Which factor is NOT likely to increase bulk density in soils? A. High organic matter content B. Drought conditions C. Soil compaction D. Heavy machinery use Answer: High organic matter content (A) High organic matter content tends to reduce bulk density by improving soil structure and porosity. 22. Which practice is beneficial for improving soil texture in lowland or paddy soils? A. Use of crystalline amendments B. Application of organic matter C. Incorporation of sand D. Frequent tillage Answer: Application of organic matter (B) Adding organic matter enhances soil texture by improving structure and water retention in lowland soils. 23. What is a common characteristic of sodic soils? A. High pH values B. High organic matter content C. Low sodium content D. Excellent drainage Answer: High pH values (A) Sodic soils often have high pH values due to the accumulation of sodium ions, affecting soil health. 24. Which practice may alleviate zinc deficiency in soils effectively? A. Use of urea as fertilizer B. Adding excessive organic matter C. Application of phosphorus fertilizers D. Spraying with foliar fertilizers containing zinc Answer: Spraying with foliar fertilizers containing zinc (D) Spraying plants with foliar fertilizers containing zinc directly improves zinc availability and alleviates deficiency. 25. What is the effect of waterlogging on soil conditions? A. Improves water drainage B. Leads to anaerobic conditions C. Promotes organic decomposition D. Enhances aeration Answer: Leads to anaerobic conditions (B) Waterlogging typically creates anaerobic conditions that can harm root health and soil biota. 26. Which property primarily influences the retention of nutrients and moisture in soils? A. Soil pH B. Soil texture C. Soil color D. Soil bulk density Answer: Soil texture (B) Soil texture directly affects how well the soil retains nutrients and moisture through its particle size distribution. 27. Which factor primarily influences particle rearrangement in soil formation? A. Temperature variations B. Parent material composition C. Water movement D. Biological activity Answer: Water movement (C) Water movement significantly affects how soil particles rearrange during the soil formation process. 28. What is the main function of the nutrient leaching process in soil? A. To increase soil compaction B. To remove excess nutrients and salts C. To promote organic matter decomposition D. To enhance mineral content Answer: To remove excess nutrients and salts (B) Nutrient leaching is primarily the process of removing excess nutrients and salts from the soil. 29. Which soil horizon forms right above the bedrock? A. Transition horizon B. Weathered parent material C. Subsoil D. Topsoil Answer: Transition horizon (A) The transition horizon is the layer that marks the change between soil horizons and bedrock. 30. In soil chemistry, what does carbonation primarily contribute to? A. Nutrient uptake by plants B. Formation of carbonates like calcium carbonate C. Development of soil horizons D. Soil erosion Answer: Formation of carbonates like calcium carbonate (B) Carbonation involves the formation of carbonates, significantly impacting soil composition. 31. Which approach in soil study analyzes the physical properties of soil? A. Physics B. Chemistry C. Survey and classification D. Microbiology Answer: Physics (A) The physics approach examines the physical properties affecting soil behavior and functions. 32. What primarily defines the bulk density of soil? A. Soil texture and structure B. Soil organic matter content C. Water retention capacity D. Leaching potential Answer: Soil texture and structure (A) The bulk density is influenced by both texture and structure, affecting soil compaction and porosity. 33. Which of the following is NOT a factor affecting soil formation? A. Parent material B. Human intervention C. Living organisms D. Climate Answer: Human intervention (B) While human intervention can affect soil, it is not considered a natural factor in soil formation. 34. What effect does organic matter generally have on soil characteristics? A. Decreases soil aeration B. Enhances soil fertility and water retention C. Increases soil acidity D. Reduces nutrient leaching Answer: Enhances soil fertility and water retention (B) Organic matter plays a crucial role in improving soil fertility and enhancing its water retention capacity. 35. What is the main purpose of soil taxonomy in soil study? A. To classify soils based on their economic value B. To document soil surveys without analysis C. To predict weather patterns based on soil characteristics D. To understand relationships among different soil types Answer: To understand relationships among different soil types (D) Soil taxonomy helps organize knowledge about soils and the relationships among various soil types. 36. Which of the following best describes the characteristics of the first order of soil survey? A. It delineates land areas smaller than one hectare. B. It covers extensive areas for agricultural studies. C. It is primarily used for broad land-use planning. D. It is for regional planning and cooperation. Answer: It delineates land areas smaller than one hectare. (A) The first order of soil survey is very intensive and detailed, specifically for areas smaller than one hectare. 37. Which level of soil classification directly addresses the arrangement of soil properties? A. Subgroup B. Family C. Great group D. Order Answer: Great group (C) The great group level divides soil classification by the arrangement of characteristics. 38. What factor is NOT typically considered in land suitability classes? A. Soil nutrient content B. Erosion/runoff C. Limitations to tillage and plant rooting D. Wetness Answer: Soil nutrient content (A) While wetness, erosion/runoff, and limitations to tillage and plant rooting are considered, soil nutrient content is not specifically listed. 39. Which type of soil survey is suited for agricultural and urban planning? A. First order B. Fourth order C. Third order D. Second order Answer: Second order (D) The second order of soil survey is intensive and detailed, ideal for agriculture and urban planning. 40. Which factor is associated with soil genesis and not a property of the soil itself? A. Climate conditions B. pH levels C. Particle size distribution D. Organic matter content Answer: Climate conditions (A) Climate conditions are external factors that influence soil genesis rather than inherent properties of the soil.