Agronomy 365T Exam 1 Spring 2004 Exam Score: Name TA Lab Hour Be sure to show all calculations so that you can receive partial credit for your work! 1) List 14 of the plant essential nutrient for plant growth (excluding C, H, O). Provide the complete name of the element, one form taken up by plants and list if the nutrient is a macro- or micronutrient. Spelling and charge count! (7 points) Essential Nutrient Form taken up by plant Macro or Micro including valence 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 2) List the three nutrients categorized as secondary: (3 points) 3) What nutrient deficiencies are shown in the pictures projected. (3 points) a) b) c)
2 4) Define or explain the following terms as they relate to Soil Fertility: (2 points each, 6 points total) Liebig s Law of the Minimum ph (and indicate the normal range found for soils in the Midwest) Apoplastic Transport 5) What two factors control the differences in cation retention in soils (the lyotropic series: why ions are held in this order Al > Ca > Mg > K > Na)? (2 points each, 4 points) 1. 2. 6) Your sand greens (1% O.M) on your golf course have CEC values of only 2 meq/100g. You want to increase the CEC to enhance nutrient retention. (4 points) a) Would it be better to increase the CEC of the soil by lowering or raising the soil ph to increase the CEC? b) What other practice might you use to raise the CEC of this soil? 7) The primary function in the plant of each of these nutrients is (4 points) Nutrient Magnesium Phosphorus Primary Function in the Plant
8) CEC Calculations - Use the following data for problems a through f: (6 points) 3 Soil Test Report ph OM P K Mg Ca H Al CEC % B.S. (%) (ppm) -------------meq/100g----------------- (meq/100g) (%)? 3.0 42 0.3 0.2 9.0 12.5 2.0?? a) Calculate the CEC of this soil. b) Calculate the % Base Saturation of this soil. c) Calculate the pounds per acre of magnesium in this soil. (Hint : AFS = 2,000,000 lbs. and the atomic weight of Mg= 24g) d) What is the estimated ph of this soil? e) Should you use dolomitic or calcitic lime to raise the ph of this soil? f) Calculate the pounds per acre of phosphorus in this soil. 9) If a soil has a CEC of 30 cmol(+)/kg and a base saturation of 40% (ph 5), how much CaCO 3 (Molec. Wt. = 100g) would it take to raise this soil to a ph of 7? (2 points) 10) Clay Minerals - Match one of the clay minerals in the right column to the property listed in the left column. (5 points) Commonly found in Vertisols 1:1 clay mineral Contains interlayer potassium CEC of approximately 100 meq/100g Has significant isomorphous substitution of Mg for Al in the octahedral sheet A. Montmorillonite B. Illite C. Kaolinite
4 11) Discuss the relationship of cation exchange capacity to buffering capacity to lime requirement of soils. (5 points) 12) A golf course superintendent calls you and says that the grass in one of his fairways keeps dying even though he gives it plenty of water and fertilizer and that compaction is not a problem. You ask him the soil ph and he says, Why do you care about soil ph? You give him the following 4 (four) reasons why soil ph is so important. (4 points) 1. 2. 3. 4. 13) We know that the molecular weight of MgCO 3 = 84 g mole -1, and that the equivalent weight of MgCO 3 = 42g mole -1. We also know that the molecular weight of CaCO 3 is 100 g mole -1 and that the equivalent weight of CaCO 3 is 50 g mole -1. Show all work!!! What is the calcium carbonate equivalent (CCE) of MgCO 3? (3 points) 14) If the sieve analysis of the MgCO 3 from Question 13 showed that 80 percent of this material passed an 8-mesh sieve and 40 percent of it passed a 60-mesh sieve: a) What is the Fineness Factor for this material in the U.S.A.? (3 points) b) What is the Relative Neutralizing Value (RNV) or the Effective Calcium Carbonate Equivalent (ECCE) of this material? (2 points) [If you could not calculate the answer to Ques. 13, assume the CCE of MgCO 3 is 110%]
5 15) Based on the following information: Wheat crop transpired 2.8 million lbs of water Root volume was 1.0 % of soil volume all the way to 12 inches Wheat crop accumulates 30 lb P/acre Nutrient concentrations in soil solution and total available nutrients in top 12 inches. Total available Nutrient Soil solution concentration in top 12 inches mg L -1 lb/acre P 0.15 100 Please calculate how many lbs P acre -1 would be delivered to the wheat crop via the following mechanisms: Show all work!!! Root Interception: (2 points) Mass Flow: (2 points) Diffusion: (2 points) 16) For the three soils on display, answer the following questions. a) Estimate the C.E.C. of the upper 7 inches of Soil A, Soil B and Soil C. (6 pts.) - SHOW CALCULATIONS AND ASSUMPTIONS - Soil A (silt loam soil, 20% clay- Indiana) meq/100 g Soil B (silty clay loam, 30% clay - Indiana) meq/100 g Soil C (tropical Oxisol, 50% clay/hydrous oxides-brazil) meq/100 g b) Which soil contains the most hematite? c) Which soil contains the most montmorillonite? d). Which soil is most likely to have an anion exchange capacity at ph 4?
6 Multiple Choice Select the best answer to each question and record your answer in the blank to the left of the question number. (2 pts each) 1. Phosphorus and potassium move to root surfaces predominately by: A. root interception B. mass flow C. diffusion 2. The availability of Fe, Mn, Zn, and Cu increases as soil ph A. increases B. decreases C. exceeds 8.3 3. A soil containing 10% kaolinite, 10 % montmorillonite, and 10% illite and 4% organic matter would probably have a CEC of approximately A. 6 meq/100 g B. 12 meq/100 g C. 23 meq/100 g D. 36 meq/100 g 4. Under what conditions would a soil most likely have a significant anion exchange capacity A. a midwestern soil having a ph of 6.8 and containing predominantly illite clay B. a highly weathered soil containing kaolinite and hydrous oxides of iron and alluminum at ph 4.3 C. a midwestern soil with predominantly montmorillinite clay and a ph of 6.2 D. an alluvial soil along the Amazon River with predominately montmorillonite and kaolinite and having a ph of 6.2. 5. The typical cation distribution on the exchange sites of a fertile Indiana soil with a ph 6.5 would have the relative milliequivalents of A. acidic cations greater than basic cations with Ca and Mg being in greater amounts than K and Na B. acidic cations less than basic cations with Ca and Mg being in lesser amounts than K and Na C. acidic cations less than basic cations with Ca and Mg being in greater amounts than K and Na D. acidic cations greater than basic cations with Ca and Mg in lesser amounts than K and Na
7 6. A soil with a hydrogen ion concentration of 4.0 X 10-5 N would have a ph of A. 4.0 log 3 = 0.48 B. 5.0 log 4 = 0.60 C. 5.4 log 5 = 0.70 D. 4.4 E. 4.7 7. A soil with a ph of 4.7 would have most of its acidity as A. active acidity. B. reserve acidity. 8. If an acre of soil requires 9,000 pounds of pure calcium carbonate to raise its ph from 5 to 6, approximately how many pounds of sulfur would it require to lower the ph from 6 to 5 (Formula weight: CaCO 3 = 100 g, S = 32 g). A. 1000 lb B. 1600 lb C. 3000 lb D. 5000 lb E. 15,600 lb 9. An acid soil (ph 4.5) with a large amount of ph dependent charge can not accurately have its lime recommendations determined using the SMP Buffer (ph 7.5). Does the Buffer Method over-estimate or under-estimate lime requirement. A. over estimates B. under estimates 10. The parent material (C horizon) of a glacial till derived soil in Indiana contains mostly calcareous till (Ca saturated exchange sites and free CaCO 3 ), what is the ph of this material. A. 9.2 B. 8.2 C. 7.2 D. 6.2 E. 5.2
8 Questions 11 and 12 - Answer these two questions based on the data given Soil A Soil B Soil-water ph 5.2 5.2 SMP Buffer ph 6.7 6.4 11. Which of these Indiana soils requires more lime to raise soil ph to 6.5? A. Soil A B. Soil B C. The same, (ph = 5.2) 12. Which Indiana soil has the greater cation exchange capacity (C.E.C)? A. Soil A B. Soil B C. CEC is the same 13. Most of the cation exchange capacity on organic matter originates from: A. isomorphous substitution and it is ph dependent. B. dissociation of H from carboxylic acid groups and it is ph dependent. C. isomorphic substitution and it is not ph dependent. D. dissociation of H from carboxylic acid groups and it is not ph dependent. E. dissociation of SiOH groups on the edge of the crystal structure of the O.M and it is ph dependent. 14. Which of these materials is a good soil acidifying material, is very insoluble in water, and requires microbial activity to release acidity into the soil? A. Sulfur B. Ammonium sulfate C. Gypsum CaSO 4 D. Iron Sulfate E. CaCl 2