Agronomy Quiz 4: Soil Properties and Nutrient Cycles, Quizzes of Agricultural engineering

Download Agronomy Quiz 4: Soil Properties and Nutrient Cycles and more Quizzes Agricultural engineering in PDF only on Docsity! Agronomy 354 Quiz 4 March 21, 2007 Name___________________________________ (-5 points if not legible) Choose the best answer for each question. Questions are worth 2 points each. 1. The definition of a saline soil includes all but a) EC less than 4.0 mmho/cm. b) Soil pH of 7.5 to 8.5 but no higher than 8.5. c) Good soil physical characteristics. d) May have white deposits on the soil’s surface. 2. What is it about saline soils that causes problems with crop growth? a) The salt causes the plants to become nitrogen deficient. b) The salt increases the osmotic potential of the water in the plants and in effect causes them to drown. c) The salt is toxic to the plants. d) The salt increases the osmotic potential of the soil water making it difficult for the plants to extract adequate water. 3. The definition of a sodic soil is: a) The exchangeable sodium percentage is greater than 15%. b) The soil pH is greater than 8.5. c) The soil has poor physical characteristics. d) All of the above. 4. Plowing soils causes soil organic matter to a) increase. b) decrease. c) plowing has no effect on soil organic matter. d) either increase or decrease depending on the soil. 5. The nutrient that limits microbial activity in soils is a) carbon. b) oxygen. c) nitrogen. d) sulfur. 6. Soil organic matter is important because it a) is a source of N, P and S. b) it provides cation exchange capacity. c) it increases the soil's water holding capacity. d) all of the above e) none of the above. 7. The form of N that is most susceptible to losses from the soil is a) organic N. b) ammonium. c) nitrate. Agronomy 354 Quiz 4 March 21, 2007 8. Nitrogen can be lost from the soil by a) leaching. b) plant uptake. c) denitrification. d) volatilization. e) all of the above. 9. A home gardener is given some unidentified organic material in the fall and incorporates it into her garden plot. The next spring she notices that the lower leaves of the sweet corn are turning yellow at the tips and the yellow color is proceeding down the midribs of the leaves. What was the likely carbon:nitrogen (C:N) ratio of the organic material? a) 10:1 b) 30:1 c) 100:1 d) none of the above 10. Transformation of organic N to ammonium in soils is termed a) fixation. b) nitrification. c) volatilization. d) denitrification. e) none of the above 11. The carbon to nitrogen (C:N)ratio of microorganisms is a) 4:1. b) 6:1. c) 8:1. d) 20:1. 12. The process of denitrification requires a) nitrate. b) a carbon source. c) oxygen. d) all of the above e) a and b 13. Incorporation of inorganic nitrogen into microbial biomass is termed a) nitrification. b) immobilization. c) mineralization. d) denitrification. 14. Soil organic matter plays an important role in a) formation of soil structure. b) decreasing drainage from soils. c) increasing soil susceptibility to compaction. d) development of negative charges due to isomorphous substitution.