SSC 220

EXAM PART 2

Symbiotic biological N fixation

bacteria fix N2 to plant-available forms for plants to use

• When soil bacteria turn atmospheric nitrogen to plant available forms of nitrogen, it is called what?

Mineralization

Biological conversation of unavailable organic N into plant available inorganic N

• What process converts organic N to inorganic N?

Immobilization

Biological conversation of plant available N into unavailable organic N.

Ammonification

Conversion of organic N to ammonium by microorganisms.

– Need warm temperatures, good soil moisture, and oxygen supply.

– Makes the soil more basic.

Nitrification

Conversion of ammonium to nitrite and then to nitrate

Volatilization

Removal of N from the soil by truing it into a gas that leave the soil.

• process by which ammonia is lost from the surface of the soil.

Denitrification

Conversion of nitrate to a gas form of N (ideally N2 ).

– Need warm temperatures, low oxygen, organic matter (carbon source)

Crop uptake and removal

Removal of N by plants and then removing plant residues from the field.

Law of the minimum

“If one growth factor/nutrient is deficient, plant growth is limited, even if all other vital factors/nutrients are adequate… plant growth is improved by increasing the supply of the deficient factor/nutrient.”

Mass Flow

dissolved nutrients move to the root in soil water that is flowing towards the roots.

Diffusion

nutrients move from higher concentration in the bulk soil solution to lower concentration at the root

• When plant nutrients move along a concentration gradient, it is called what?

Root interception

roots obtain nutrients by physically contacting nutrients in soil solution or on soil surfaces.

Structural Component

Cal Hates Outside

Primary Macro

New PK

Secondary Macro

CaMgS

Non essential but beneficial

NaSiCoSeAl