Plant Nutrition Exam 1

Front 1

Plant Nutrition

Back 1

The supply and adsorption of chemical compounds needed for growth and metabolism

Front 2

Metabolism

Back 2

includes various reactions occurring in a living cell in order to maintain life and growth

Front 3

Criteria for Plant Nutrients to be Essential (3)

Back 3

1. The deficiency of the element makes it impossible for the plant to complete its life cycle or results in abnormal growth. 2. Deficiency is specific for that element or nutrient can't be replaced by another element 3. The element is directly involved in the nutrition of the plant (necessary for a specific process-- constituent of an essential metabolite, or required for the action of an enzyme system)

Front 4

Macronutrients

Back 4

C, H, O, N, P, K, S, Ca, Mg nutrients req'd in greater concentrations

Front 5

Micronutrients

Back 5

Fe, Mn, Cu, Zn, Mo, B, Cl

Front 6

Other essential nutrients

Back 6

Co, Si, Ni, Na have been established as essential for some but not all plant species Na for saline species, Si for rice

Front 7

Lists of essential nutrients will change, interest in these (3) elements

Back 7

Ni, Si, V may be essential, better instrumentation will allow detection of lower concentrations, may be essential in extremely low concentrations.

Front 8

Physiological Function and/or Biochemical Behavior Group I: (elements, uptake, forms, functions)

Back 8

- Major constituents of organic material - Elements: C, H, O, N & S - Uptake: soil solution (N & S) vs. atmosphere (C, H, O) - Forms: CO2, HCO3-, H20, O2, NO3-, NH4+, N2, SO4-, SO2 - Functions: organic matter & Enzymatic processes

Front 9

Physiological Function and/or Biochemical Behavior Group II: (elements, uptake, forms, functions)

Back 9

- Energy Transfer - Elements: P, B, & Si (both macro and micronutrients) - Uptake: soil solution - Forms: Phosphates (usually negatively charged), boric acid, & silicates - Functions: form esters w/ alcohols, phosphate esters involved in energy transfer reactions (bound by hydroxyl groups of sugars forming esters)

Front 10

Physiological Function and/or Biochemical Behavior Group III: (elements, uptake, forms, functions)

Back 10

Free ions or organic matter - Elements: K, Na, Mg, Ca, Mn & Cl - Uptake: soil solution - Forms: ions (K+, Na+, Mg2+, Ca2+, Cl-, Mn2+) - Functions: free ions or organic ions in plant, osmolites, enzymatic activation, ionic balance, and membrane permeability(Ca)

Front 11

Physiological Function and/or Biochemical Behavior Group IV: (elements, uptake, forms, functions)

Back 11

Metals, electron transport, & catalysts - Elements: Fe, Cu, Zn, Mo - Uptake: soil solution - Forms: ions and/or chelates - Functions: electron transport (valency change) & catalysts (accenting or getting rid of electron pairs)

Front 12

Chelate

Back 12

an organic molecule which contains 2 or more atoms which are able to bind to the same metal atom thus forming a ring structure

Front 13

Composition of Plants (%) (3)

Back 13

1) Water - 70% or greater 2) Organic Material - about 27% (depending on water composition) 3) Minerals - 3% (stays the same)

Front 14

Factors Controlling Mineral Composition of Plants (4)

Back 14

1) Genetic capacity (fixed nutrient uptake potential; species dependent) 2) Nutrient Availability (based on: pH, if nutrient is present in soil) 3) Plant Organ (leaf, root, flower, etc.) 4) Plant age (generally lower w/ age)

Front 15

General Mineral Composition of Plants (N, P, K)

Back 15

- N and K concentration about 10 x greater than P and Mg - P and Mg about 100-1000 x greater than micronutrients - N sufficiency range: 1.5-6% - P sufficiency range: .15-1%

Front 16

Three Phases in Soil Medium

Back 16

1) Solid - main nutrient reservoir - inorganic particles- K, Na, Ca, Mg, Fe, Mn, Zn, & Cu - organic particles - N, some P & S 2) Liquid -nutrient transport system -mainly as ions w/ exception of CO2 and O2 3) Gas - exchange of CO2 & O2 between living entities in soil & in the atmosphere * This is a dynamic system

Front 17

% of Soil Componenets

Back 17

Air - 25% Water- 25% Mineral Particles - 45% Organic Matter - 5% (within organic matter-- 10% organisms, 10% roots, 80% humus)

Front 18

Soil Colloids

Back 18

suspended particles that are not going to settle out, mainly of clay & humus, very small particles w/ chemically reactive surfaces

Front 19

Colloidal Fraction of Soils

Back 19

1) organic portion or humus 2) Inorganic portion or clay

Front 20

Cation Exchange

Back 20

Movements of ions between colloid surfaces and soil solution

Front 21

Organic Fraction of Soils

Back 21

- Chemical and physical nature changes w/ decomposition - Takes on colloidal properties - Carbs form CO2 & H20 polyuronides synthesized by microorganisms (important in soil structure) - partial decomposition of lignins form phenolic & carboxylic groups (Increasing CEC) - usually negatively charged coloid surface, H usually released which acidifies soil, creates (-) charged cation exchange site

Front 22

Organic Fraction Continued

Back 22

- Proteins decompose, liberating ammonia - organic matter closely associated w/ clay fraction, may penetrate clay layers, preventing further decomposition - CEC may be reduced by 20-50% if removed - organic raction is only about 3-5% of mineral soil mass

Front 23

Soil Structure vs. Soil texture

Back 23

Soil Structure- how soil particles are put together Soil Texture- distribution of soil particles

Front 24

Inorganic Fraction of Soil

Back 24

Soil Texture - clay, (silt, sand, gravel -- very little role in CEC) - most important clay minerals are the layer silicates

Front 25

2 forms basic building blocks involved in Layer Silicates (type of clay minerals)

Back 25

1) Tetrahedron (Si) 2) Octahedron (Al3+, can be replaced by Mg2+ or Fe2+) form layers when attached in a plane

Front 26

3 Major Clays

Back 26

1) Kaolinite (1:1) - one octahedron, one tetrahedron layer; held very tight, preventing water & cations from moving between layers 2) Micas (2:1)- high negative charge in tetrahedron layer, satisfied by K+ 3) Smectite (2:1) - held together by weakly hydrated cations, esp Ca+2 A lot more CEC from 2:1 clays, ions are less tightly held

Front 27

Ion Exchange

Back 27

Exchange of ions in soil solution & soil complex (colloids or humus)

- reversible process by which cations & anions are exchange between the solid & liquid phases if in close contact

- soil colloids are amphoteric (have acid & basic characteristics), bind both cations & anions

Front 28

Cation Exchange Capacity

Back 28

- measure of the total negative charge of a soil - expressed in milli-equivalents (1 mg H+ or the amnt. of any other ion that will displace it) per 100 g of dry soil (the larger the particles, the more CEC will be reduced)

Front 29

Mineral Fraction CEC

Back 29

- from clay & some silt - negative sites created by 1) Isomorphous ionic substitution (Si or Al atom substituted for); dialent cation for trivalent ion. Evenly distributed through clay particles. 2) Ionization of hydroxyl groups; at corners & edges of plane SiOH + H20 <---> SiO- + H30

Front 30

Organic Fraction CEC

Back 30

- arise from -COOH, -OH, and NH2 groups having H+ disassociated from them

Front 31

Cations are subjected to: (2)

Back 31

1) Interionic forces-bound tightly 2)kinetic forces -- termal motion;dissociation an equilibrium is reached between soil particle, exchangeable cations, & free solution *very dynamic system

Front 32

Degree to which cations are bound depends on (2) :

Back 32

1) the charge of the cation; higher the charge, stronger the bond in general 2) Hydration; higher hydration, weaker the bond

Front 33

Anion Adsorption

Back 33

- Small for most soils compared to cation adsorption

Front 34

Two forms of anion adsorption

Back 34

1) ligand exchange w/ OH groups 2) Adsorption to protonated groups

Front 35

Ligand Exchange

Back 35

- Anion replaces hydroxyl group(s) Me--OH- +anion- <----> Me--anion + OH- - Phosphorus & sulfur w/ iron & aluminum oxides (held tightly) - pH dependent reactions, favored by low pH (loss of H+) - phosphorus maybe rendered unavailable at low pH - lime can reverse the reaction, making phosphorus available - chemical reaction and more anion specific

Front 36

Adsorption to Protonated Groups

Back 36

- favored at low pH - OH group is protonated - NO3- and Cl- are held in this way (nitrate easily leached out of soil) - electrostatic interaction and is non-anion specific

Front 37

Anion Adsorbers

Back 37

- Hydrous iron and aluminum oxides (typically held to Fe, S) - Calcium carbonates (limestone, Fl & Al) - 1:1 clays - 2:1 Clays - Iron and aluminum organic complexes

Front 38

Buffering Capacity

Back 38

- ability of H+ ions to exchange for other cation species on soil colloids - High CEC soils have higher buffering capacities (provided exchange sites are saturated with cations other than H+)