Section 1 - Test 1 Flashcards by Brandon Holland

Which of the following is not expected to increase in the coming 50 years?

water consumption
area of farmlamd
food production
human population

area of farmlamd

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Crop yield potentials are limited by climatic, soil, and crop factors. Thanks to modern science and research, all these factors are eliminated and crop production has reached its maximum limit.

True
False

False

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If you methodically and sequentially eliminate the most limiting crop growth factors, the yield will increase indefinitely.

True
False

False

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U.S. crop yields have increased greatly over the last 50 years due to the following reasons except:

breeding improved varieties
use of fertilizer
population growth
improved nutrient and pest management

population growth

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If you ash a plant sample and analyze it for all its constituents, you will only find the 17 essential nutrients we discussed in this class

True
False

False

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Plants and animals need the same 17 essential nutrients to complete their healthy life cycle.

True
False

False

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The three primary ways plant nutrients reach plant root doesn’t include:

solar radiation
mass flow
diffusion
root interception

solar radiation

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The reason why gypsum (CaSO4.2H2O) is not a liming material is that it doesn’t have an anion that will neutralize ____________.

H+
SO4-2
Na+
Ca+2

H+

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Which of the following is defined as acid-neutralizing capacity of a liming material expressed as a weight percentage of CaCO3?

CEC
SAR
CCE
ESP

CCE

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You added 100 lb P/a to soil A and B, and the equilibrium solution P concentration in soil B is four times greater than that of A, although plant uptake of P was greater in soil A than in B. Based on this information, which of these soils have a greater buffering capacity?

soil A
soil B
It is difficult to determine from the given information.
both have the same buffering capacity

soil B

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You can say plants are on liquid diet because they get their soil based essential nutrients from soil solution.

True
False

True

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__________ nutrient concentration occurs somewhere in the transition between nutrient deficiency and sufficiency.

critical range
luxury consumption
toxicity range
sufficiency range

critical range

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Solution A has a pH of 4.0, and solution B has a pH of 7.0. The active acidity of soil A is ____________________ than that of B.

1000X less
3X less
3X more
1000X more

1000X more

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Why does AU Soil Testing lab doesn’t test soils for plant available N, but makes recommendations based on field trials?

Because analyzing for N is very difficult and expensive
Because N deficiency can be noticed visually and N test is unnecessary
There is no significant source/reserve of N in the soil to measure potential availability
All Alabama soils are rich in N and N test is not important

There is no significant source/reserve of N in the soil to measure potential availability

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Although a lot of acidity is produced by natural and anthropogenic processes, the change in pH is not as low as expected because there are many natural and anthropogenic processes that will encounter the acidity.

True
False

True

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The ratio law of cation exchange capacity states that, at equilibrium, the ratio of the cations on soil colloids and the soil solution will be the same.

True
False

True

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How many lbs of CaCO3 will be needed to neutralize acidity generated by oxidation of ammonium phosphate per lb of N according to the following reaction? (Molecular weights in grams, H=1, C=12, N=14, O=16, and P=31.)

NH4H2PO4 + 3O2 ->NO3- + H2PO4- +2H+ + 3H2O

7.2

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Since PBS + PAS = 100%, it is correct to assume that as PBS increases, PAS will also increase because CEC is not affected by the type of cations on the exchangeable site.

True
False

False

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Since soils in the contiguous US have similar properties, soil testing labs in the US use the Adam-Evans buffer solution as modified by Dr. G. to make the correct quantity of lime recommendations.

True
False

False

Which of the following process does not help release ions and nutrients to soil when the nutrient concentration in the soil solution decreases as the plant roots absorb nutrients?

weathering
adsorption
dissolution
desorption

adsorption

Which of the following would increase the CEC of soil?

increasing the weathering intensity
decreasing the concentration of organic matter
increasing soil pH from 5.5 to 7.5
decreasing isomorphous substitution

increasing soil pH from 5.5 to 7.5

Which of the following term represent the H+ concentration in soil solution?

exchangeable acidity
active acidity
residual acidity
potential acidity

active acidity

The best advice you can give to someone whose soil pH=5.0 and if s/he wants to grow alfalfa that grows well at pH=7.0 is either lime the soil to pH 7.0 or find a crop that grows best at pH=5.0.

True
False

True

Which of the following ion is not dominant in alkaline soil?

HCO3-
OH-
H+
CO3–

H+

Under which of the following condition will a mineral precipitate relative to its solubility product constant (Ksp)? Assume it dissolves to produce the same number of ions. when the product of the ions concentration is = Ksp when the product of the ions concentration is >Ksp when the products of the ions concentration is

when the product of the ions concentration is >Ksp

What would be the PBS (% base saturation) of 100 g of soil with the following cations exchanged on the surface: 3Al+3, 4Mg+2, 1Na+1, and 6Ca+2 ions? (Hint: calculate the CEC first.) (M.W. in grams Na=23, Mg=24, Al=27, Ca=40). 30% 85% 70% 41%

70%

Both nitrogen fixation by soil microbes and nitrogen fixation by clay minerals are considered gains for soil solution N. True False

False

In which of the following processes is nitrogen cycled with no net gain or loss in the soil-plant-atmosphere continuum system? immobilization volatilization removing seed to for sale adding fertilizer

immobilization

How do the newly formed leaves of a plant remain green when symptoms of chlorosis are displayed by other older leaves? due to more active absorption of N protein from soil by newer leaves due to conversion of soluble N in older leaves to bound protein due to translocation of converted soluble N to the newer leaves due to loss of protein N from chloroplasts in older leaves

due to translocation of converted soluble N to the newer leaves

Why is lime traditionally applied every 2-3 years to reduce soil acidity? Because liming materials have an expiration dates of 2-3 years Because there is too much potential acidity that is only partially neutralized by liming. Because liming material do not contain gypsum that could have eliminated acidity for good. Because active acidity cannot be neutralized by liming.

Because there is too much potential acidity that is only partially neutralized by liming.

Rice is being cultivated in a highly irrigated field with nitrate fertilizers regularly applied to improve cultivation. Due to low soil absorption, the soil is sometimes waterlogged. After some time, the farmer records loss in crop yield and detects chlorosis related to N deficiency. What could be a possible reason? high denitrification potential of the soil low immobilization potential of the soil high nitrification potential of the soil low mineralization potential of the soil

high denitrification potential of the soil

The standard recommendation to reclaim saline-sodic soil is by applying a dilute concentration of Na+ regularly to improve water infiltration and then washing it with water concentrated with Na2SO4. True False

False

________ converts to NO3- in soil. nitrosomonas pencillum thiobacillus nitrobacter

nitrobacter

Nitrogen is the most limiting plant nutrient, hence it needs to be applied for increased food production. Since excess N also causes eutrophication, a balance should be developed where crop production and environmental quality do not suffer. True False

True

Relatively speaking, coated/slow-release nitrogen fertilizers are expected to enhance eutrophication because of their extended N availability to plants and in the environment. True False

False

In Habor-Bosch fertilizer production, N2 + H2 will react to form _________________. NO3- urea NH3 NH4+

NH3

If a plant residue with C:N = 100 is added to soil, organic matter N mineralization will accelerate while immobilization will retard. True False

False

Natural rainforests around the world exist without N fertilizer applications. Their sources of N does not include: N-fixation by soil microbes wet and dry N depositions N-mineralization N-volatilization

N-volatilization

As fertilizer N application to soil increases, microbial N fixation will increase synergically to produce more N for plants. True False

False

Animal manures are becoming an important source of plant N. Some of the disadvantages of these sources include: improving soil structure improving water holding capacity low N fertilizer grade increasing soil CEC

low N fertilizer grade

All exchangeable cations on a 50-g soil were displaced by 1M NH4AOc at pH=7 and, then NH4+ was displaced by K+ (KCl) and the solution was collected in 500 mL volumetric flask. The NH4+ was determined to be 720 ppm in the solution. Calculate the CEC of the in meq CEC/100 g or cmolc/kg of soil. (M.W. in grams H=1, N= 14.)

CEC = (720mg/L)(0.5L/50g)(1molc/18g)(100cmol/mol)(1g/1000mg)(1000g/1kg) = 40cmolc/kg = 40meq/100g

Calculate the amount of pure CaCO3 that could theoretically neutralize the H+ in five‐year acidrain if a 1‐hectare (ha) site received 300 mm of rain per year and the average pH of the rain was 4.0. (Hint: a hectare is 100 m x 100 m.) (M.W. in grams, H=1, C=12, O=16, Ca=40)

ph = 4.0 therefore H=10^-4 = 0.0001 mol/L Volume = 0.3x5x100x100 = 15,000 m3 H(EQ) = (0.0001mol/L)(15000m3)(1000L/m3)(1molc/1mol) = 1500 molc/ha CaCO3 (eq) = (100g/mol)(1mol/2molc) = 50g/molc CaCO3 (required) = (1500molc/ha) (50g/molc) = 75000g/ha = 75kg/ha

If a total of 300 lb/a of N as NH4NO3 was applied for 20 years to a corn farm, calculate the amount of pure CaCO3 needed to neutralize the acidity generated due to oxidation of NH4NO3? Use this reaction if necessary: NH4NO3 +2O2 -->2NO3- +2H+ +H2O (M.W in grams H=1, C=12, N=14, O=16, Ca=40).

CaCO3 (lb/lbN) = (2*50)/(1*14) = 7.14 (lb/lbN) Total N applied = 300lb/a/yr x 20yr = 6000 lb/a CaCO3 required = (7.14)(6000) = 42840 lb CaCO3/a

How many grams of pure CaCO3 would you need to apply to an acidic soil with 100% exchangeable Al saturation to reduce it to 20%? The CEC of the soil is 40.0 meq/100 g or cmolc/kg soil. (M.W. in grams: C=12, O=16, Al=27, Ca=40)

CEC = (40cmolc/kg soil)(1-.2)(1mol/100cmol) = 0.32 molc/kg soil CaCO3(EQ) = (100g/mol)(1mol/2molc) = 50g/molc CaCO3 (required) = (0.32 molc/kg soil)(50g/molc) = 16g/kg soil

How many grams of gypsum (CaSO4.2H2O) would you need to reclaim sodic soil with an exchangeable sodium percentage (ESP) of 80% to reduce it to 10%? The CEC of the soil is 40 meq CEC/100 g soil or 40 cmolc/kg soil? (M.W. in grams H=1, O=16, Na=23, S=32, Ca=40)

CEC = (40)(0.8-0.1)(1/100) = 0.28 molc/kg soil CaSO4.2H2O (EQ) = (172g/mol)(1mol/2molc) = 86g/molc CaSO4.2H2O (Required) = (0.28 molc/kg soil)(86g/molc) = 24.08 g/kg soil