Crss 4590 - exam 2 (copy)

3 organic forms of N

manure: 20-60% N mineralization

meals: blood has highest N ~15%, bone is high in Ca and P, feather has fastest decomposition

3 inorganic forms of N

Urea

Ammonium nitrate

Ammonium sulfate

urea

CO(NH₂)₂

50% of world’s N fertilizer use

46.6% N

needs 3.6 kg CaCO₃ / kg N used

ammonium nitrate

NH₄NO₃

34% N

Acidic

needs 3.6 kg CaCO₃ / kg N used

can be surface-applied

ammonium sulfate

(NH₄)₂SO₄

21% N

needs 7.2 kg CaCO₃ / kg N used

surface applied, no NH₃ loss in soils with pH <7.5

behavior of MAP in soils

monoammonium phosphate

water-soluble, dissolved in moist soils, and releases ammonium and phosphate

7.2 kg CaCO₄ / kg N added as MAP

3 fertilizers that contain only nitrate

Calcium nitrate

Potassium nitrate

sodium nitrate

advanages and disadvantages of slow-release fertilizers

advantages: release rate matches plant requirements, less frequest applications

disadvantages: cost, plant wont get needed nutrients as soon as it’s added

how inorganic slow release fertilizers work

compounds are often water soluble and coated with a closed-ring structure, as water breaks down this structure nutrients will slowly leak out and into the solution

how organic slow release fertilizers work

as the organic material slowly breaks down the nutrients will be released in the soil solution

what determines if an element is essential

if the absence of an element hinders the physiological performance of a plant to a certain level then that nutrient is considered essential

primary macronutrients

N, P, K

secondary macronutrients

Ca, S, Mg

nitrogen uptake in plants

mostly taken up as ammonium (NH₄) or nitrate (NO_3^-)

nitrate transport mechanism in plants (3)

channel transporters: above-ground portion

HATS: high-affinity transport system for low concentration of N

LATS: low-affinity transport system for high concentration of N

uniporter

high-affinity nitrate transport system, binds to solutes and carries across membrane

lacks co-transportation

symporter

low-affinity AND high-affinity nitrate transport system

co-transport with protons and nitrates

ammonium transport mechanisms (4)

AMT classes:

3 assists in the uptake of ammonium in root hairs

1 found internally, assists in moving ammonium across barriers

what other forms of N can be taken up by plants

amino acids and proteins

ammonium uptake

must be attached to a carbon-containing compound to be transported

nitrate uptake

can either be assimilated into roots, remain in roots, or transported from root to shoot

the preferred form of N by plants (due to flexibility)

reduction requires ATP

steps to nitrite reduction

1. convert nitrate to nitrite (requires NADPH or NADP)

2. convert nitrite into ammonium (requires 6FDred or 6FDox)

   1. step depends on presence of nitrate, light, and carbohydrates

3. convert inorganic ammonium into amino acids (requires GS-GOAT)

   1. step 3 happens directly after step 2, if there is not enough energy for step 3 to happen then step 2 will be delayed

GS-GOAT reaction steps

1. ammonium is incorporated into an organic molecule (glutamine)

2. ammonium is added to the carbon backbone (glutamine synthesis)

3. glutamine combines with 2-oxoglutarate, creating 2 molecules of glutamine

molybdenum in nitrite reductase

is required as a co-factor for nitrite reductase. if it is not present then reductase will not occur

Biological N fixation bacteria name

rhizobia

enzyme used in biological N fixation

nitrogenase enzyme, breaks N=N bonds

what can inactivate the nitrogenase enzyme

oxygen

what transports oxygen to bacteria in biological N fixation

leghemoglobin in nodules

steps to formation of rhizobia nodules

1. compounds from plant attract bacteria

2. compounds from bacteria are recognized by plant, establishing symbiotic relationship

3. root hairs extend, bacteria enters

4. bacteria create infection thread while moving towards inside of root

function of nitrogen in plants

proteins: rubisco

chlorophyll

nucleic acids

symptoms of N deficiency

symptoms first appear in older leaves, chlorosis

forms of P in soil

mineral P

solution P

soil organic matter

types of solution P

H₂PO₄ : distributed as a function of pH

HPO₄

movement of inorganic P in solution

moves from soil to roots by diffusion

types of organic P in soil

inositol: plants and manures

phospholipids: plant membrane

nucleic acids

P mineralization

transforms organic P into inorganic P which is then used by plants

enzyme that releases P in mineralization

phosphotase

adsorption of P

fast process, adsorped by clay minerals

in acidic soils: P precipitates as Fe/Al P

in basic soils: P adsorbed on CaCO₃ and clay minerals

P adsorption equation

Q = ac_^b

factors affection P fixation

soil minerals (Fe/Al, 1:1 clays, CaCO₃)

soil pH: maximum availability at 6.5

anion effect: competition by other anions

OM, time

organic P fertilizer

manure: .4-2.5% P, low N/P ratio

bone meal: 4.2% P

synthetic inorganic P fertilizer

rock phosphate: 21-47% P₂O_5, acidic soils

phosphoric acid: 39-55% P₂O₅, can be applied directily to soils

behavior of P fertilizer in acidic soils

P will move to the soil solution, which is then taken up by clay minerals, making less P available for plants

apply fertilizer in a band to decrease contact with soil

forms of K in soil

exchangeable K: present in CEC (only 2% of K in soil and is the only form that can be used by the plant)

non-exhcnagable K: associated in CEC but cannot be exchanged

primay mineral K: parent material

primary K minerals

feldspar, micas (muscovite, biotite)

list the rate of primary K mineral reactions

biotite > muscovite > feldspar

why non-exchangable K cannot be used

the K is fixed in 2:1 clays and trapped between the interlayers

can be released when layers are propped up with heat

movement of solution K

diffusion (90%) and mass flow (10%)

leaching of K

occurs in sandy soils

what can affect leacing

the material that K is attached to:

sulfate is more bound to soils, so it has less leaching

chlorine floats free in solution, which attaches to K and allows leaching

organic source of K

manure: .2-2% K

important K minerals

sylvite: potash, KCl

K fertilizers

potassium chloride (KCl): 60% K₂O

potassium sulfate (K₂SO₄): 50% K₂O

sul-po-mag: 22% K₂O

potassium nitrate: 44% K₂O, 13% N

feedstock material used for industrial fixation of N

methane from natural gas

common fertilizers that contain only N

urea (high % N), ammonium nitrate (high acidity)

materials that can and cannot be used with urea-ammonium nitrate solutions

should: PVC, stainless steel

should not: alumminum, brasso

organic and inorganic slow release N fertilizer

organic: blood and other meals

inorganic: triazone (water soluble, rings break down)

loss of N when urea is applied to soil with pH 6

the ammonium is kicked from CEC sites into solution when pH increases, it then turns to ammonium_aq and eventually turns into ammonium_g and dissapates

main forms of organic P in soils

inositol and phospholipids

two processes involved with P fixation

adsorption: through clay minerals

precipitation: precipitates as Ca-P

what pH does Ca-P begin to precipiate at

pH above 7

process that limits P availability at pH < 6.5

Fe and Al oxides reduce at pH lower than 6.5

what does available P in fertilizer terminology

how much P is readily available for plant uptake

raw materials used to produce P fertilizers, what soil conditions can the raw material be used directly onto soils

rock phosphate, acidic soils

chemical form in which P is present in inorganic P fertilizers

phosphate

a P fertilizer that can decrease soil pH

MAP, contains ammonium which acidifies soil

a P fertilizer that has no effect on soil pH

superphosphate, no N is present

two potential advantages of using manures as an organic P fertilizer

high P availability, contains nitrogen and is cheap

why manure leads to a buildup of soil P and how to avoid buildup

manures contain high P:N ratios, avoid by applying by P requirement, not N

why P buildup in soil is a problem

P reduces plants ability to take up other micronutrients and causes toxicity

why is it difficult to measure mineralization of organic P in soils

P is rapidly adsorped by clay minerals in the soil

two primary minerals that release K into the soil

Micas and feldspars

biotite > muscovite > feldspars

list the following fertilizers in increasing order of susceptibility to K leaching:

K2SO4, K3PO4, KCl

K2SO4 leaches the least because SO4 is bound to soil, KCl will leach the greatest because the Cl is not bound to soil

K2SO4 > K3PO4 >KCl

why is non-exhcangable K found in some soils

they are found in 2:1 clays

fertilizer that does not affect soil pH

KCl

main form of K in animal manure, approximate avaiability

.2-2%, 90% available