Agron 354 Exam 2
You have a large planter box in a greenhouse that contains 708 kg of soil. A soil test shows that you need to neutralize 3.2 meq/100 g of acidity. How many (grams) of finely ground (100% available) pure CaCO3 is required to neutralize the acidity of this soil?
1133 divide meq of lime by valence so 50 then take that times CEC so 160 take that times the soil weight then divide by 100
What is meq weight (mg/meq) of Mg 2+ if the atomic weight is 24?
12 atomic weight/ valence
If a soil can hold 160 mg of Mg2+ per 100 g, how many meq per 100 g of charge is required to saturate CEC?
13.3 atomic weight/ valence then mass of Mg/100g soil X meq/ 12
Your soil test report calls for 2590 lbs of ECCE per acre at a 6-in. depth, but you wish to incorporate the lime to only a 4-in. depth. How much ECCE is required?
1726.67 take your 6in / your other inches then take your lbs divided by that answer
If a soil has 11.0 x 10^21 negative charges per 100 g, how many meq per 100 g of charges does this equal?
18.3 11.0x 10^21/ 6.022x 10^20
A common way to determine CEC of a soil is to saturate the CEC with NH4+ ions. If a soil holds 365 mg of NH4+ per 100 g, what is its CEC?
20 atomic mass NH4/ valence = 18 365 mg NH4/ 18
A soil solution has a pH of 8.5. What is the H+ concentration of the soil solution? (NOTE: must answer with scientific notation of examples 1.11E-06 or 1.11x10-6)
3.16x10^-9 take the pH to the 10 so 10^8.5
If a soil contains 3.4% organic matter, 27% montmorillinite clay, 16% illite clay, and 2% kaolinite clay, what is a reasonable estimate of the CEC in meq/100g of this soil? See table for CEC of minerals or soil organic matter (SOM). Kaolinite 1:1 nonexpand H - bonding 8 Illite 2:1 nonexpand K ions 30 Montmorillonite (aka smectite) 2:1 expand Mg and Al ions 80 Vermiculite 2:1 expand Mg ions 150 Organic matter 200
33.4 divide the %'s by 100 and then multiply those by the CEC of the clay and then add those together
Your soil test report calls for 5 lbs ECCE per acre. If the quarry's limestone is 10% CaCO3 equivalent and 1% effective, how many tons of limestone from this quarry must be applied to a 181-acre field to satisfy this ECCE?
452.5 multiply the equivalent and the effective then take the ECCE / the last answer then take that X the amount of acres then divide by 2000
What is the percentage base saturation of a soil with these ions per 100 g: Ca =73.0 meq, H = 47.0 meq, Mg= 35.0 meq, Na= 5.0 meq, K = 3.0 meq, and Al = 16.0 meq?
64.7 add together all the meq then only add together the bases (ca, na, k, mg) then take the bases # / the whole # and multiply by 100
A soil has a pH of 6.9. What is the pOH?
7.1 14-6.9
If 90% of a limestone sample from an Iowa quarry passes a 4-mesh sieve, 76% passes an 8-mesh sieve, 70% passes a 20-mesh sieve, and 63% passes a 60-mesh sieve, what is an estimate of the availability based on fineness of this sample?
70 if talking about iowa never use the 20 mesh 4 mesh= .1 8 mesh=.3 60 mesh=.6 take the % and multiply it by the factor for the appropriate mesh and then add the products to each other
A soil solution contains 0.00000001 M H+. What is the soil pH?
8
What is the pH of a solution that contains 0.0000000077 M H+?
8.1 -log(.0000000077)
Calculate and show work in determining the calcium carbonate equivalency of slag or CaSiO3 (in percent).
86 find the molecular weight of CaSiO3 and also find the molecular weight of CaCO3 (its 100 all the time) then divide CaCO weight by CaSiO3 weight X 100
Your analysis of 100g of soil indicates that it will hold 100 mg of Ca2+ (at wt= 40g) when saturated with this ion. what is the CEC of this soil in meq/100g? A.)5 B.)10 C.)15 D.)20 E.)25
A.) 5
A soil with a high cation exchange capacity is certain to have a high: A.) Buffer capacity B.) Exchangeable acidity C.) Level of soil fertility D.) pH
A.) Buffer capacity
Which of the following is expected to increases as the pH drops fro 7 to 4? A.) anion exchange capacity B.) cation exchange capacity C.) hydroxyl ion concentration D.) percent base saturation E.) potassium availability
A.) anion exchange capacity
The detrimental effects of a soil pH below 5.0 are primarily the result of: A.) toxicity from excess Al, Mn, and H+ ions B.) a deficiency of OH- ions for plant growth C.) changes in concentrations of other ions D.) dispersing the clay particles E.) low water quality
A.) toxicity from excess Al, Mn and H+ ions
What is the correct order of materials from lowest CEC to greatest CEC ( Increasing from left to right): A.)kaolinite(1:1)<montmorillonite (2:1)<humus B.) vermiculite(2:1) < illite (2:1) < kaolinite (1:1) C.) humus < kaolinite (1:1) < montmorillonite (2:1) D.) humus < montmorillonite (2:1) < kaolinite (1:1) E.) montmorillonite (2:1)< humus< kaolinite (1:1)
A.)kaolinite(1:1)<montmorillonite (2:1)<humus
This plant uptake mechanism is when plants take up nutrients AGAINST the electrochemical potential or gradient. A.) Passive transport B.) Active transport C.) Casparian transport D.) Simple transport E.) None of the above
B.) Active transport
Active acidity in a soil is best related to: A.) Al3+ on exchange sites B.) H+ in solution C.) Na+ in parent materials D.) Ca2+ in limestone E.) lime requirement
B.) H+ in solution
Cation exchange capacity is an important soil property in plant growth because: A.)Increased CEC increases soil pH B.) Increased CEC increases storage potential for bases C.) Increased CEC reduces nutrient fixation D.) Increased CEC implies greater clay content
B.) Increased CEC increases storage potential for bases
Which of these does NOT happen when an acid soil in limed to a neutral pH? A.) the rate of nitrification increases B.) the rate of nitrogen fixation decreases C.) the CEC of the soil increases D.) the availability of phosphorus increases E.) the availability of manganese decreases
B.) the rate of nitrogen fixation decreases
Why can't one use only the pH, and not base saturation, of a soil to determine the soil's lime requirement?
Because pH only looks at active acidity or lime requirement. Base saturation also takes into account reserve acidity or the buffering capacity of the soil
Which groups of nutrients can all be taken up by plants as anions? A.) P, N, Cu B.) Ca, Mg, B C.) B, S, P D.) Mg, N, Zn E.) Zn, Cu, Cl
C.) B, S, P
When nitrate ions are equally abundant throughout the soil solution, they can be expected to reach the plant roots mostly by: A.) diffusion B.) eluvation C.) mass flow D.) Root interception
C.) Mass flow
Which of these crops would grow almost as well on a soil at pH 5.0 as on a soil at pH 6.8? A.) alfalfa B.) corn C.) oats D.) sweet clover E.) soybeans
C.) Oats
The best explanation as to why aluminum is considered an acidic cation is: A.) it releases Ca and thereby increases pH B.) it absorbs H+ and causes it to precipitate C.) it reacts with water and releases H+ D.) it reduces the ability of a soil to hold cations
C.) it reacts with water and releases H+
A nutrient solution deficient in Ca2+ is most likely to produce plants with: A.) Low levels of protein B.) spindly growth with long internodes C.) wrinkled younger leaves D.) red-colored petioles E.) yellowing along the margin of older leaves
C.) wrinkled younger leaves
Indicate three common basic ions found in Iowa soils
Ca 2+ Mg 2+ K + Na +
A solution has a concentration of .00001 M H+ ions. what is the expected pOH of this solution? A.) 3 B.) 5 C.) 7 D.) 9 E.) 11
D.) 9
According to the lyotropic series which one of these cations is the most strongly attached to the soil colloids? A.) NH4 + B.) Ca 2+ C.) H + D.) Al 3+ E.) Mg 2+
D.) Al 3+
Which of the following types of high pH soils are common in Iowa fields? A.) saline-sodic B.) saline C.) sodic D.) calcareous E.) high gypsum
D.) calcareous
Which of these is NOT an acid-forming factor in soil? A.) addition of ammonium-containing fertilizer B.) movement of water through soil leaching out bases C.) removing basic cations with harvested biomass D.) power-plant scrubbers removing sulfuric acid E.) oxidation of S compounds
D.) power-plant scrubbers removing sulfuric acid
Which of the following statements is true about strongly weathered soils (oxisols): A.) They are mostly 2:1 clays B.)They tend to have a high pH C.)The have high soil organic matter content D.)They have higher anion exchange capacity E.) None of the above
D.) they have a higher anion exchange capacity
A soil test indicates a need for 3200 lb of ECCE per acre, and the available lime has a CEC of 90% and an effectiveness of 70% based on fineness. The application rate should be set at ______. A.) 2000 B.) 2200 C.) 3200 D.) 4500 E.) 5100
E.) 5100
All of the following soils have the same pH, which one will require the most lime to bring to pH of 6.5: A.)Silt loam B.)Sandy loam C.)Sand D.)Loam E.)Clay loam
E.) Clay loam
The pH of rain water in the USA, away from industrial areas, is expected to be slightly acidic because of waters reaction with ______. A.) phosphoric acid B.) sulfuric acid C.) argon gas D.) oxygen E.) carbon dioxide
E.) carbon dioxide
This specific source of charge in soil is NOT pH dependent. A.) anion exchange capacity associated with soil organic matter B.) cation exchange capacity associated with soil organic matter C.) broken bonds on the edges of clays giving anion exchange capacity D.) broken bonds on the edge of clays giving cation exchange capacity E.) charge coming from isomorphic substitution
E.) charge coming from isomorphic substitution
A compound is said to be amphoteric, which means: A.) it has high AEC B.) it has high CEC C.) it releases proton ions D.) it releases hydroxyl ions E.) it can release either protons or hydroxyl ions
E.) it can release either protons or hydroxyl ions
What are the chemical available forms of these nutrients (show correct valence): two forms of available N two forms of available P one form of available K
N: NO3 -, NH4 + P: H2PO4 -, HPO4 2- K: K +
Describe what is meant by a 1:1 clay versus a 2:1 clay with regard to the structure of clays.
The ratios are representative of how many tetrahedral to octahedral sheets are found in a clay layer. these sheets are what makes the shape and chemical comp differ
True or false The reaction rate of limestone is quicker with smaller mesh lime.
false
Explain how mass flow supplies nutrients to a root
water is taken up by the plant, nutrients are dissolved in solution. A lot of nutrients are taken up this way
