Section 2 - Test 2 Flashcards
The two forms of P available for plant uptake in soil at pH 5-8 will be:
H3PO4 and H2PO4-1
H2PO4-1 and HPO4-2
H3PO4 and HPO4-2
HPO4-2 and PO4-3
H2PO4-1 and HPO4-2
Phosphorus is an essential element, but it could be replaced by silicate (H2SiO2) or arsenate (HAsO3) since they have similar chemical behavior.
True
False
False
When a large quantity of biosolid is applied to soil, a negative P sorption will take place. This will result in:
P deficiency for plant uptake
Low equilibrium phosphorus concentration at EPC=EPC0
less soil solution P
excess P in soil solution
excess P in soil solution
The amount of P fixed by soil microbes from the air atmosphere is comparable to the P deposited from particulate deposition.
True
False
False
Which of the following process will add P to the soil solution?
precipitation
adsorption
absorption
desorption
desorption
Loam soils have a higher P buffering capacity (PBC) than sandy soils. This means:
Sandy soils will maintain higher solution P
Loam soils do not maintain high solution P
Sandy soils do not fix high quantity of P
Loam soils will not fix high quantity of P
Sandy soils do not fix high quantity of P
The percentage of P2O5 in CaHPO4.2H2O is: (molecular weight in g H=1, O=16, P=31 and Ca=40)
- 7
- 5
- 1
- 5
41.5
What is the most essential function of P in plants?
It is the main chelating agent.
It acts as a catalysts for enzymatic actions.
It stores energy and transfer it.
Since it not part of any plant structure, it has no any specific function.
It stores energy and transfer it.
Potassium will substitute for N and becomes a major component of chlorophyll and protein when nitrogen is deficient in plants.
True
False
False
Due to its role in plants, it is safe to say that, “Potassium is a chemical policeman of cell metabolism”.
True
False
True
Which of the following fertilizer has a K2O of 83% when chemically calculated? (elemental mass in grams: H=1, C=12, N=14, O=16, K=39.)
KNO3
K2CO3
KOH
KCl
KOH
Which of the following actions would improve the K availability of 1:1 kaolinitic dominated soil?
Adding S to acidify the soil.
Adding K fixing minerals to the soil.
Adding more kaolinite to the soil.
Adding a mica mineral to the soil.
Adding a mica mineral to the soil.
Historical P mining data shows that there is no “peak”, and the global P ore resources will last as much as N fertilizer resources.
True
False
False
If Brandon Holland wants to start a business of manufacturing P fertilizer instead of thinking about growing environmentally friendly sustainable vegetable production, which of the following raw materials should be his primary requirement?
single superphosphate
liquid N and a pH meter
rock phosphate
urea-ammonium phosphate
rock phosphate
Considering the different P minerals that will precipitate at different pHs, if there were NO low pH precipitating phosphate minerals such as Al, Fe, Mn and etc., the apatite Ca-P minerals would have been the best P fertilizers because of their high solubility at low soil pH.
True
False
True
Ca and Mg are taken by plants as Ca+2 and Mg+2 at low pH, and as Ca-2 and Mg-2 at high pH and aerobic conditions.
True
False
False
Which of the following factors would increase the mineralization of S in soil?
incorporating plant residues with a low C:S ratio of 100:10.
incorporating crop residue with C:S of 400-600.
limiting microbial activity
low sulfatase activity
incorporating crop residue with C:S of 400-600.
The main reason most soils in the Southeast US are not deficient in Ca is:
Ca is added as an acidifying material
Ca is added with acidrain precipitation
Ca is added as liming material
All soils are naturally rich in Ca and application is never needed.
Ca is added as liming material
Plants are responding to sulfur fertilizer since the Clean Air Act, especially in the Southeast US states, such as Tennessee, Alabama, South Carolina, and others. This is due to:
increase in soil acidity due to acidrain
reduction in SO2 pollution of the air
increase in soil organic matter
increased application of cheaply available gypsum.
reduction in SO2 pollution of the air
Organic S mineralization is not affected by:
soil organic matter
soil nitrogen gas content
soil temperature
C:N:S ratio of a plant residue
soil nitrogen gas content
At low soil pH, S can react with Al and forms a strong bond that renders it from becoming readily plant available on soils rich in kaolinitic and oxides colloids.
True
False
True
Plants take sulfur mainly as:
SO4-2
S3O5
elemental S
SO2
SO4-2
Sulfur performs a dual role in soil fertility. It is an essential plant nutrient and it lowers soil pH (increases acidity).
True
False
True
Luxury consumption of K by plants has significantly reduced eutrophication problems that could have resulted from the high K load soil sediments.
True
False
False
The bond strength of P adsorption to Al oxides in increasing order can be arrayed as diffused/soil solution P> inner-sphere P complex > outer-sphere P complex.
True
False
False
The best method to determine if there is enough soil P for plant growth is to test the total P content of the soil using different soil extraction methods.
True
False
False
Since as pH increases, the availability of Fe, Mn, Zn, and P increases while the availability of Mo, K, and N decreases, correcting soil pH is highly recommended to manage these nutrients.
True
False
False
If it were not for the cost of buying micronutrient fertilizers, applying excess amounts of them to soil is recommended for future needs since they will do no harm to plants and the environment.
True
False
False
Which of the following is an essential plant nutrient but not a beneficial nutrient per the current classification?
Cobalt (Co)
Nickel (Ni)
Vanadium (V)
Selenium (Se)
Nickel (Ni)
Which of the following fertilizer contains about 69% Fe when chemically calculated? (Molecular weight Fe =56, S=32, P=31, O=16, C=12, and H=1 g.)
FeSO4
Fe2(SO4)3
FeCO3
Fe2O3
Fe2O3
Micronutrients bound in chelate rings lose their ability to act as ions and are therefore not likely to take part in chemical reactions that precipitate them or otherwise render them available for plants.
True
False
True
Why is a foliar application of some micronutrients is recommended as opposed to the regular soil application?
To enhance precipitation reaction of the deficient nutrient
To increase plant availability of the nutrient.
To decrease plant availability of the nutrient
To decrease metabolic activity of the nutrient.
To increase plant availability of the nutrient.
The use of natural organic or synthetic chelating of micronutrients will:
may cause deficiency by forming organo-metalic ligands
enhances their availability to plants
decrease their availability to plants
increases their toxicity to plants
enhances their availability to plants
Phosphorus retention/sorption is defined as a continuous sequence of which of the following processes?
desorption and adsorption
dissolution and precipitation
precipitation and adsorption
desorption and precipitation
precipitation and adsorption
Mineral solubility line represents the __________ maintained in the soil solution by a specific mineral under standard conditions.
minimum equilibrium concentration of the dissociating ion in solution
maximum equilibrium concentration of the dissociating ions in solution
the quantity of the solid mineral
the potential concentration of the H+ activity in soil solution
minimum equilibrium concentration of the dissociating ion in solution
Which of the following is not true regarding K deficiency in plants?
Deficiency symptoms are identical with that of N
Deficiency symptoms consist of white spots on the leaf edges
Deficiency symptoms usually appear first in upper leaves and progress towards the older leaves.
Deficiency symptoms appear in all leaves at the same time.
Deficiency is observed through chlorosis and necrosis of older leaf edges.
Deficiency symptoms are identical with that of N
Deficiency symptoms consist of white spots on the leaf edges
Deficiency symptoms usually appear first in upper leaves and progress towards the older leaves.
Deficiency symptoms appear in all leaves at the same time.
Among the different fractions of K in soil, the least amount is contained in the __________ fraction.
nonexchangeable
all are about the same under normal conditions
exchangeable
soil solution
soil solution
If you add a large quantity of crop residue with a C:P ratio of 400:1 to soil, and you observed symptoms of P deficiency in the plants growing in the soil, what would be the logical reason for your observation?
P eutrophication
The soil cannot be P deficient because of the large quantity of residue added
P mineralization
P immobilization
P immobilization
Soil and plant profiling of a farm reveals poor adsorption of sulfate as a reason for poor crop yield. Which of the following practices could rectify the situation?
Adding aluminum oxides
adding gypsum (CaSO4.2H2O)
adding crop residues and manures with C:N:S ratio of 400:100:1
acidifying the soil
adding gypsum (CaSO4.2H2O)
Source of fertilizer S does not include
open pit S ore mining
dry and wet S precipitation
fixation of S as FeS2
mineralization of organic matter
fixation of S as FeS2
Assume you are a soil-plant nutritionist who knows how to calculate the balance between P in manure and plant uptake. If a certain agricultural practice produces 6000 lbs residue/a with 0.3% P content, calculate the
amount of manure with 1.5% P that needs to be applied to meet the plant needs assuming all P will be available during plant growth?
Solution
P in residue = 6000 x 0.003 = 18 lb/a
Amount of manure needed = X x 0.015 =18
X = 18/0.015 = 1,200 lb/a
A soil has a CEC = 20 meq/100 g with 20% and 2%, Ca and Mg saturation, respectively. Calculate the lbs/a of CaCO3 and MgSO4 needed to increase Ca and Mg saturation to 75% and 10%, respectively. (Molecular weights in g C=12, O=16, Mg=24, S=32, Ca=40.)
Solution:
Ca in the soil = 20 meq /100 g x (0.75 – 0.20) x 20 mg Ca/meq = 220 mg Ca/100 g = 0.220 g/100 g = 0.220 lb Ca/100 lb = 0.220 lb Ca x 20,000 = 4,400 lb Ca/a
CaCO3 needed = 4,400 lb Ca/a x 100/40 = 11,000 lb/a
Mg in the soil = 20 meq /100 g x (0.10 – 0.02) x 12 mg Mg /meq = 19.2 mg Mg/100 g = 0.0192 g/100 g = 0.0192 lb Mg/100 lb = 0.0192 lb Mg x 20,000 = 384 lb Mg/a
MgSO4 needed = 384 lb Mg /a x 120.3/24.3 = 1,901.0 lb/
A soil contains 5% soil organic matter (SOM) with an annual mineralization rate of 2%. (a) Calculate the amount of N and P mineralized per/a from SOM assuming SOM contains 58% C, 5% N, and 0.5 P) and (b) the C:N:P in the SOM
Solution:
Amount of OM /A = 0.05 x 2,000,000 lb = 100,000 lb/a Amount of OM Mineralized/a = 100,000 lb x 0.02 = 2,000 lb/a Amount of C in the OM Mineralized/a = 2,000x 0.58 = 1,160 C lb/ Amount of N mineralized/a= 2,000 lb x 0.05 =100 lb N/a Amount of P mineralized/a= 2,000 lb x 0.005 =10 lb N/a C:N =1160/100 =11.6:1 or 58/5 =11.6:1 C:N:P : 1,160 : 100 :10 : 116:10:1
A soil contains 2% OM with 1% mineralized each year (8:1 N:S). A clover crop grown on this soil yields 8,000 lbs/a (N:S = 12:1, 3% N content. (a) Calculate the amount of S mineralized each year (lbs/a), (b) Is the mineralized S enough for S needed? (c) How many lbs/a of CaSO4.2H2O would be required if S mineralized in (b) is not enough? (Assume 5% N in mineralized organic matter.) (Molecular weights in g (H=1, O=16, S=32
Solution
Amount of OM /a = 0.02 x 2,000,000 lb = 40,000 lb/a Amount of OM Mineralized/a = 40,000 lb x 0.01 = 400 lb/a Amount of N mineralized/a= 400 lb x 0.05 = 20 lb N/a Amount of S mineralized/a= 20 lb x 1/8 = 2.50 lb S/a Amount of S in clover = 8,000 x0.03 x 1/12 =20 lb Additional S needed 20.0‐2.50 = 17.5 lb Amount of S needed from CaSO4.2H2O = 17.5 x 172/32 = 94.06 lb
If a plant residue contains 7500 kg C and 30 kg P, how many grams of H2PO4- you need to add to your soil to avoid net immobilization of P? (Use C/P=250 as no net gain or loss)
C/P = 250 no P‐immobilization. Thus, 7500 kg /(30 kg + P) = 250 250P kg + 7500 kg = 75000 kg P = (75000‐7500)/250 = 0 kg
