Nutrient Management Flashcards
Macronutrients (type/mobility in plants/uptake form)
Nitrogen (NH4+, NO3-) mobile
Phosphorus (H2PO4-, HPO4^2-) mobile
Potassium (K+) mobile
Calcium (Ca^2+) immobile
Magnesium (Mg^2+) mobile
Sulfur (SO4^2-) immobile
Micronutrients (name/uptake form)
Boron (H3BO3, H2BO3^-)
Chlorine (Cl-)
Copper (Cu2+)
Iron (Fe^2+, Fe^3+)
Manganese (Mn^2+)
Molybdenum (MoO4^2-)
Nickel (Ni^2+)
Zinc (Zn^2+)
Function of Nitrogen
Used in synthesis of amino acids, proteins enzymes
Found in chlorophyll (photosynthesis)
ADP, ATP (energy transfer)
Function of Phosphorus
Important component of energy transfer system (ADP, ATP)
Important to photosynthesis and respiration
Part of cell nuclear material important to cell division
Function of Potassium
Accelerated growth of meristematic tissue
Regulation of stomata open ring (water loss)
Involved in N and carb metabolism
Catalyze some enzymes
Function of Sulfur
A component of several amino acids (cystine,cysteine, methionine) which are part of many proteins
Involved in protein synthesis and enzyme activation
Forms flavor compounds in mustard, garlic, and onions
How does nutrient need change as plant growth progresses from germination to maturity
Plant nutrient demands gradually increase during the seedling stage, rapidly increases during vegetative growth, and decreases again as reproductive growth dominates
What is the role of soil solution in supplying nutrients from the soil
Plant nutrients dissolved in the soil solution and are made available for plant absorption through the processes of mass flow, diffusion, and roof interception
What is the role of cation exchange sites in supplying nutrients from the soil
Cation exchange sites located on clay particles and organic matter hold cations and can be released into the soil solution to be readily available to plants
What is the role of organic matter in supplying nutrients from the soil
Can be a source of nutrients (N, P, K) when decomposed
Holds onto cations by cation exchange and chelation
What is the role of soil minerals in supplying nutrients from the soil
Dissolved soil minerals can release nutrients into the soil solution
Clays, carbonates, and hydroxides can also retain nutrients by adsorption on their surfaces
What is the role of plant residue in supplying plant nutrients from the soil
Plant residue contains the essential elements that are returned to the soil system as the plant residue decomposes and rainfall leaches soluble nutrients from the plant residue
Describe nutrient mineralization
The release of a nutrient when an organic material (SOM, manure, biosolids) is decomposed by soil microorganisms
It is the conversion of a nutrient from organic to inorganic form
Describe immobilization
When a nutrient is converted from an inorganic to organic form
During decomposition, the nutrient is incorporated into microbial cells and SOM
Describe uptake antagonism between ions
Two or more ions may compete for plant uptake by various mechanisms
One ion is said to be more antagonistic with regard to the uptake of another ion
Describe mass flow
Occurs when a nutrient moves to a plant root with the water that is being absorbed by the plant
Important uptake process for N, Ca, Mg
Describe Diffusion
The movement of a nutrient to a plant root due to a concentration gradient between the soil solution and the root surface. The nutrient concentration is higher in the soil solution than at the root surface so the nutrient moves to the root surface
Important nutrient uptake process go P, K
Describe root interception
Occurs when a root grows next to a clay or OM surface and absorbs the nutrients.
Usually means the root has grown near a soil colloid and absorbed the nutrients on or near the colloid surface
Usually a minor way nutrients are absorbed
How does soil nutrient uptake occur at the root surface
Passive (nutrient enters root with water that is being absorbed)
Active processes where the nutrient is moved into the by a molecule or ion termed a carrier
Define Cation exchange capacity
The amount of positively charged cations that can be held by a given weight of soil
Units are color+charge/kg of soil (equivalent to meq/100 g soil)
How does CEC influence nutrient mobility of cations and anions
As CEC increases , the mobility of cations decreases as they are held on the cation exchange sites.
Leaching of soluble anions (nitrate, chloride, sulfate) increases as CEC increases.
What influences CEC
Increases in Clay mineral type (1:1 vs 2:1 clays), organic matter and soil pH generally increase CEC
What cations are retained on cation exchange sites
Calcium, Magnesium, and Potassium.
Can become immobile.
I’d routine additions of a cation occur, the added cation can change places with Ca, Mg, or K on the CEC releasing them into the soil solution.
What forms of Nitrogen are mobile and immobile in the soil
Nitrate (NO3-) is mobile
Ammonium (NH4+) is immobile
Explain when phosphate is mobile/ immobile in the soil
Phosphate is immobile in soil except where P sprouting capacity has been exceeded
Is sulfate mobile or immobile in the soi?
Immobile
When are cations mobile/immobile in the soil?
When on exchange sites, Ca, Mg, and K are immobile.
When cations are in the soil solution they are mobile
Describe how texture affects nutrient uptake
The more clay in a soil, the more likely there will be available nutrients.
Leaching of nutrients increases as souls become more sandy because sandy soils have larger pores allowing fewer water movement and have a small cation and anion exchange capacity
Describe how structure affects nutrient uptake
Soil structures that create large pores will increase the potential for nutrient losses through leaching
Lack of structure can lead to increases in runoff and erosion
Describe how drainage/aeration affect nutrient uptake
If drainage is poor, anaerobic conditions may occur, causing increased solubility in Iron and Manganese and the loss of nitrate by denitrification
Nutrient losses are associated with excessive drainage
Describe how moisture affects nutrient uptake
Adequate soil moisture is important for nutrients that move to roots by diffusion (P)
Adequate moisture favors decomposition of and release of N,P, and S from the material undergoing decomp.
As soil moisture decreases, insoluble compounds containing nutrients often form.
Describe how soil pH affects nutrient uptake
Soil pH affects the availability of most nutrients due to physical (leaching/volatilization), chemical (adsorption/desorption/precipitation), and biological processes (mineralization/immobilization) that change with pH
Extremes in soil pH can alter absorption of nutrients by roots by changing root metabolism
Describe how temperature affects nutrient uptake
The influence of temperature can be through plant metabolism where a min/optimum/max temperature for nutrient uptake exists and can change with plant growth and development
Temperature can also affect the rate of decomposition of organic material
Describe how ammonium fixation by clay affects the fate of N in soil
Some 2:1 clay minerals that contain negative charge in the tetrahedral layer near the surface of the clay can fix the ammonium ion rendering it unavailable for plant uptake
Slow release of this ammonium ion occurs over long Time periods
Describe how ammonification affect the fate of N in soil
Ammonification converts organic N to ammonium by microorganisms as they decompose OM and release ammonium into the soil
Describe the process of nitrification
Ammonium is oxidized to nitrite (NO2-) by microorganisms. Requires water, hydrogen ions, and energy for microorganisms
Nitrite is oxidized to nitrate by soil microorganisms. Requires oxygen and produces energy for microorganisms.
What affects the rate of ntrification
Soil temp (below 50degF), soil pH below 5 and above 8, and low soil moisture decreases nitrification
What is Volatilization?
The conversion of ammonium to ammonia gas.
What conditions favor volatilization?
High temp (ammonia is less soluble in water)
High soil pH (more ammonium concerted to ammonia)
Low soil CEC (less ammonium adsorbed by soil colloids)
Moist/wet soil (favors formation of ammonia)
Windy weather (increases ammonia gradient from soil to atmosphere)
Large amounts of surface residue (prevents ammonium adsorption)
When does denitrification occur
When soils are waterlogged /flooded
Soil microorganisms will use nitrate for metabolism when oxygen is depleted from the soil
What are the products of denitrification
Gaseous dinitrogen (N2) and gaseous oxides of nitrogen that move to the atmosphere
What conditions favor denitrification?
Nitrate present
Oxygen absent
Organic compounds are available as an energy source
Near Neutral pH
Warm soil temp