Soil Chemistry MCQ's PDF

What is the primary function of earthworms in soil? ANSWER: Decompose organic matter to humus and recycle nutrients What is the term for the total amount of organic matter living in the soil? ANSWER: Soil Biomass What is the role of mycorrhizal fungi in soil? ANSWER: Enhance water holding capac...

What is the primary function of earthworms in soil? ANSWER: Decompose organic matter to humus and recycle nutrients What is the term for the total amount of organic matter living in the soil? ANSWER: Soil Biomass What is the role of mycorrhizal fungi in soil? ANSWER: Enhance water holding capacity, bind soil particles together, and help with disease resistance What is the process of converting organic matter into humus? ANSWER: Humification What is the term for the area around a plant root where the biological and chemical aspects of the soil are influenced by the root? ANSWER: The Rhizosphere What is the benefit of adding organic matter to soil? ANSWER: Improves soil structure and fertility What is the definition of a symbiotic relationship? ANSWER: A relationship where two or more organisms live in close contact, where at least one benefits, and neither are harmed What is the purpose of adding lime to soil? ANSWER: To raise the pH to a suitable level What is the ideal temperature for soil to be considered warm, and how does it affect the growth of plants? ANSWER: Above 10 degrees Celsius, as it allows for optimal growth and microbial activity. What is the purpose of cultivating soil, and how does it relate to the carbon cycle? ANSWER: Cultivating soil helps to aerate it, which is essential for the decomposition of organic matter and the release of carbon dioxide in the carbon cycle. How do farmers reduce their carbon footprint, and what is the significance of afforestation in this process? ANSWER: Farmers reduce their carbon footprint by planting more trees (afforestation), reducing diesel usage, growing biofuels, not burning straw, and using minimum tillage. Afforestation helps to sequester carbon dioxide from the atmosphere. What is the relationship between Soil Organic Matter (SOM) and Soil Organic Carbon (SOC), and how is SOC calculated? ANSWER: Soil Organic Carbon (SOC) is calculated by multiplying the percentage of Soil Organic Matter (SOM) by 0.58. What are the different forms of nitrogen in the nitrogen cycle, and how do they relate to each other? ANSWER: The forms of nitrogen are nitrogen gas (N2), nitrate (NO3-), ammonium (NH4), and nitrite (NO2-). They are interconverted through various processes such as nitrogen fixation, decomposition, nitrification, and denitrification. What is the role of bacteria in the nitrogen cycle, and how do they contribute to nitrogen fixation, nitrification, and denitrification? ANSWER: Bacteria play a crucial role in the nitrogen cycle by decomposing organic matter, fixing nitrogen, nitrifying ammonium to nitrate, and denitrifying nitrate to nitrogen gas. What is the main effect of adding organic matter to a soil with low CEC? A. Increase in nitrate ions availability B. Decrease in the concentration of H+ ions C. Increase in the amount of negative charges on soil colloids D. Increase in the availability of Mg2+ cations ANSWER: C Which cation is not commonly found in soils? A. Ca2+ B. Mg2+ C. Na+ D. K+ ANSWER: C What is the optimum pH range for most plant growth? A. 5.5 - 7.5 B. 4.5 - 5.5 C. 6.0 - 8.0 D. 7.0 - 9.0 ANSWER: A What is the role of lime in soil? A. To reduce the availability of Ca2+ cations B. To reduce the CEC of the soil C. To increase the availability of H+ ions D. To increase the amount of negative charges on soil colloids ANSWER: D What is the primary reason why cations are attracted to soil particles? A. Because cations have a neutral charge B. Because soil particles have a negative charge C. Because soil particles have a positive charge D. Because cations have a positive charge ANSWER: B What type of ions determine the acidity of the soil? A. Alkaline ions B. Neutral ions C. Basic ions D. Acidic ions ANSWER: D What is the result of the adsorption of cations onto the surface of soil particles? A. Polarized water holds soil particles together B. Soil particles become more dispersed C. Soil particles become electrically charged D. Flocculation is inhibited ANSWER: A What is the effect of liming on soil? A. Increases the amount of acid leaching B. Reduces acid leaching C. Reduces the amount of negative charges on soil colloids D. Increases the availability of Al3+ ions ANSWER: B What is the typical CEC of sandy soils? A. Medium B. Low C. High D. Variable ANSWER: B Why does humus have a higher Cation Exchange Capacity (CEC) than clay? A. Because humus has a lower concentration of anions B. Because humus has a higher charge density than clay C. Because humus has a higher concentration of cations D. Because humus has a larger surface area ANSWER: D What is the benefit of high humus content in soil in terms of flocculation? A. It reduces the rate of flocculation B. It increases the rate of flocculation C. It only occurs in clay soils D. It has no effect on flocculation ANSWER: B What is the effect of pH on CEC? A. As pH decreases, CEC increases B. pH has no effect on CEC C. As pH increases, CEC decreases D. As pH increases, CEC increases ANSWER: D What is the role of cations in cation exchange? A. They replace anions on the surface of soil particles B. They are adsorbed onto the surface of soil particles C. They are fixed to the surface of soil particles D. They are released into the soil solution ANSWER: B What is the significance of the Cation Exchange Capacity (CEC) of soil? A. It measures the ability of the soil to adsorb and exchange cations B. It measures the amount of water held by the soil C. It measures the pH of the soil D. It measures the amount of nutrients available to plants ANSWER: A Why can a cation with a +2 charge (Ca2+) replace two separate cations each with +1 charge (H+)? A. Because H+ has a lower charge density B. Because the charges are equivalent C. Because Ca2+ has a higher charge density D. Because Ca2+ has a higher valency ANSWER: D