Plant Nutrition Andrew G. Ristvey Wye Research and Education Center Maryland Cooperative Extension College of Agriculture and Natural Resources University

Plant NutritionPlant Nutrition

Andrew G. Ristvey Andrew G. Ristvey Wye Research and Education CenterWye Research and Education Center

Maryland Cooperative ExtensionMaryland Cooperative Extension

College of Agriculture and Natural ResourcesCollege of Agriculture and Natural ResourcesUniversity of MarylandUniversity of Maryland

January 2008January 2008

Plant NutritionPlant Nutrition

Master Gardener ProgramMaster Gardener Program

Objectives for this topic include:* The essential macro and micronutrients necessary for plant growth and the basic mechanisms for availability and uptake of nutrients.

* Organic and inorganic fertilizers and how they are used by the plant.

* The negative effects of over-applied or mis-applied fertilizers.

* Appropriate timing of fertilizer application and fertilization for special situations

Growth Factors: What do plants need to grow?

1.

2.

3.

4.

5.

6.

What is an essential plant nutrient?

The criteria for essentiality: Arnon and Stout, 1939

All the nutrients needed to carry out growth and reproductive success; full life cycle

2. The element cannot be replaced or substituted

1. Omission of the element will result in abnormal growth

3. The element must exert its effect directly on growth


There are 17 known (accepted) elements that are essential for plant growth

Hydrogen, Oxygen, Carbon – plant gets from air and water

The other 14 are mineralized elements derived from soil (or air as in N)

Other nutrients being studied:

Silicon, Cobalt, Aluminum

Relationship between plant growth and nutrient concentration

• What happens when a nutrient or nutrients are inadequate in supply?

• Can the concentration of a nutrient be too high?

von Liebeg’s ‘Law of the Minimum’

Plant growth progresses to the limit imposed by the nutrient in least supply


von Liebeg’s ‘Law of the Minimum’Plant growth progresses to the limit imposed

by the nutrient in least supply


tires chassis engines

Nutrient % ppmNitrogen 1.5

Potassium 1.0

Calcium 0.5

Magnesium 0.2

Phosphorus 0.2

Sulfur 0.1

Chlorine 100

Iron 100

Manganese 50

Boron 20

Zinc 20

Copper 6

Molybdenum 0.1

Nickel 0.05?

Mac

ron

utr

ien

tsM

icro

nu

trie

nts

Forms in which nutrients exist

• cation – positively charged ion

• anion – negatively charged ion

• neutral – uncharged

• Plants used the mineralized from of a nutrient– It does not matter to the plant where it comes from

So which nutrients exist in what form?

• ammonium – NH4+

• potassium – K+

• calcium – Ca+2

• magnesium – Mg+2

• iron – Fe+2, Fe+3

• zinc - Zn+2

• manganese Mn+2, Mn+4

• copper – Cu+2

• cobalt – Co+2

• nickel – Ni +2

• nitrate – NO3-

• phosphate – H2PO4- , HPO4

-2

• sulfate - SO4-2

• chlorine – Cl-

• borate - H3BO3, H2BO3-, B4O7

-2

• molybdate – MoO4-2

AnionsCations

Factors that affect nutrient uptake

• Getting nutrients to the plant roots– Nutrients are water soluble

• What factors affect nutrient availability– pH– Cation Exchange Capacity

• Colloids (humus, clay)

Getting nutrients to the roots: Mechanisms for nutrient delivery

• mass flow– the passive movement of nutrients in soil water to

roots

• diffusion – the movement of nutrient from regions of high

concentration to regions of low concentration

• root interception– direct contact of nutrients with roots as roots grow

and explore soil

Getting nutrient to the roots: Mechanisms for nutrient

delivery

Properties Affecting Nutrient Availability

p = potential or powerH = hydrogen

Chemical Properties - pH

• pH and hydrogen ion concentration are inversely related.

• As pH increases, hydrogen ion concentration decreases.


• Logarithmic scale pH of 6 has 10x more H+

than pH 7

pH [H+] [H+]1 10-1 .1

2 10-2 .01

3 10-3 .001

4 10-4 .0001

5 10-5 .00001

6 10-6 .000001

7 10-7 .0000001

8 10-8 .00000001

9 10-9 .000000001


Chemical Properties - pHpH affects the availability of nutrients


Chemical Properties – Cation Exchange CapacityC E C

• ammonium – NH4+

• potassium – K+

• calcium – Ca+2• magnesium – Mg+2

• iron – Fe+2, Fe+3

• zinc - Zn+2

• manganese Mn+2, Mn+4

• copper – Cu+2

• cobalt – Co+2

• nickel – Ni+2

• nitrate – NO3-

• phosphate – H2PO4-HPO4

-2

• sulfate - SO4-2

• chlorine – Cl-

• borate - H3BO3, H2BO3-, B4O7

-2

• molybdate – MoO4-2

Cations Anions


Growing Media - Growing Media - Chemical Properties Chemical Properties - pH

OH-

OH-

OH-

OH-

H+ H+

H+

H+

H+

H+

H+

H+

H+

H+

H+

H+

H+ H+

H+H+

H+

H+

H+

H+

H+H+

H+

H+

H+

H+H+

H+

OH-

pH affects the availability of nutrients

Negatively charged chemical groups OH- on humic particlesSometimes associated with Fe and Al in clays

pH High or Low ?

Low

Growing Media - Growing Media - Chemical Properties



H+

H+H+

H+H+

H+

H+

OH-

OH-

OH-

OH-

OH-

Negatively charged chemical groups OH- on humic particlesSometimes associated with Fe and Al in clays

pH High or Low ?

High


The ability of a soil or substrate to provide a nutrient reserve

It is all the exchangeable cations the soil or substrate can adsorb

The CEC of a soil depends on colloids and pH


The higher the CEC of a soil the better buffering capacity

attracts

Chemical Properties – Colloids and CEC

Colloids - very small particles in soil that are chemically reactive (charged) – humus, clay

K+Fe++

Mg++

Mn++

H+

Fe++

Mg++

Mg++

Mn++

H+

H+

Ca++

K+

+




Chemical Properties - Colloids and CEC

OH-

OH-

OH-

OH-

OH-

Example of one scneario: some nutrients become more available at low pH

Mn++

Mn++

Mg++

Mn++

Mn++ Mg++

Ca++

Fe++

Fe++

Fe++

Fe++

Fe++



Chemical Properties – CEC

OH-

OH-

OH-

OH-

OH-

H+ ions vie for space, certain ions released becoming available

Mn++

Mn++

Mn++

Mn++

Mn++

Mn++

Ca++

Fe++

Fe++

Ca++

Fe++

Fe++

H+H+

H+

H+

H+

H+

H+

H+

H+

H+

H+ H+

H+H+

H+

H+H+

H+

H+

H+H+

H+

pH ≈ 5.8


The ability of a soil or substrate to provide a nutrient reserve

Types of Soil Colloids Cation Exchange Capacity

(cmolc/kg of colloid)

humus 100-300

vermiculite 120-150

montmorillonite 60-120

illite 15-40

0-3* iron oxides


10 – 10 – 10

What’s on the BagN P K

# - # - #

N

1.00

N

0.44 0.83–

–

–

–P K

– P2O5 – K2O

The Major Players – N and P

• Nitrogen

– NO3- N and NH4

+-N or urea

• Phosphorus

– H2PO4--P at pH of 5.0 to 6.5

Nitrogen (N)

– NO3- N and NH4

+-N or urea

utilized for a variety of structural and metabolic compounds

over half of N in plants is found in the leaves of plants

between 15 and 30% of that leaf nitrogen goes into the production of Ribulose 1-5-biphosphate carboxylase or Rubisco

Nitrogen is very mobile within the plant

NO3- nitrate

Nitrogen (N)

taken up by plants passively and actively uptake increases pH in soil

best uptake pH range between 4.5 and 6

nitrate can be stored in plant nitrates leach

taken up by plants passively and actively decreases pH in soil

ammonium (ammonia) cannot be stored

must be assimilated immediately by carbon

NH4+ ammonium

ericaceous species utilize

Nitrogen (N)

Phosphorus (P) H2PO4

- -P at pH of 5.0 to 6.5

High pH, P binds with calcium

Low pH P, binds with iron High P fertilizers do not promote root growth

Utilized for energy transfer, membrane structure, nucleic acids,proteins

Mobile in plant

Nutrient Interactions: Relationships of elemental excess in growing media to potential nutrient deficiencies in plant tissue.

Element in excess in media

Element possibly deficient in plant tissue

Nitrogen as ammonium Potassium, Calcium, Magnesium

Potassium Nitrogen, Calcium, Magnesium

Phosphorus Copper, Zinc, Iron

Calcium Magnesium, Boron

Magnesium Calcium, Potassium

Sodium Potassium, Calcium, Magnesium

Manganese Iron, Molybdenum

Iron Manganese

Zinc Manganese, Iron

Copper Manganese, Iron, Molybdenum

Molybdenum CopperAluminum: this element is not essential and high levels are rare in artificial soils. High Aluminum will precipitate Phosphorus as Aluminum Phosphate and can highly reduce short term Phosphorus availability.

Mobility of Plant Nutrients: Mobility of elements in the plant often defines the location of visual symptoms of nutrient deficiencies or toxicities:

Very Mobile

ModeratelyMobile

LimitedMobility

Nitrogen Magnesium Iron

Phosphorus Sulfur Manganese

Potassium Molybdenum Copper

Chlorine Zinc

Calcium

Boron

** Most recently matured leaves are the most Most recently matured leaves are the most accurate leaf sample for nutrient analysis.accurate leaf sample for nutrient analysis.

Nutrient Form:Organic or Inorganic?

• Plants used the mineralized form of a nutrient– It does not matter to the plant where the nutrient comes from,

as all nutrients taken up are in a mineralized form

– See handout on types of organic and inorganic fertilizers

• However adding composted organic matter to your soil will aid in nutrient availability– See lesson on soils

Nutrient Form:Composts and Teas?

• Composts are denatured organic materials– A true aerobic compost requires 3 things

• Aeration

• Moisture – 40 to 60 %

• A C:N ratio of 30 to 1

• Anaerobic composting – less heat, more break down,

increased humus production, but more noxious gases

• Making teas from composts is easy, however making a consistent product is not

– Anti-pathogen properties

Foliar Nutrient Application• Plants use the mineralized form of a nutrient

– The majority of nutrient uptake are via plant roots

– Nutrients can be applied via foliar application

– Foliar application should merely be supplemental• For most nutrients

– If foliar application is the primary method of nutrition something is wrong with your soil ! (or roots)

Other Negative Effects of Nutrient Over-application

• Runoff

• Physiological responses may affect root growth

e.g. recent evidence shows P does not promote root growth may affect flowering

e.g. over application of N and other nutrients may stimulate vegetative growth as in grapes

• Inappropriate fertilizers NO3 is not well utilized by ericaceous species

• Balance your NO3 with your NH4 good for most plants

Timing of Fertility

• Evidence of periodicity in nutrient uptake in some species• evidence for opposite shoot growth/root uptake periods• fall uptake for spring growth

• Arborist stress fall fertilization of trees and shrubs

• Some concern over cold hardiness issues with fall N fertility

• Lawn care specialists suggest fall fertilization

• Tree nursery recommendations stress split fertilizationearly spring and mid summer

Fertility - special situations • Drought fertility Water is the most important growth regulator

Fertilizing under drought conditions is not recommended

No water, no growth regardless nutrients

High EC’s in soil can damage roots

• New Plantings Recent recommendation discourage fertility with new plantings

Watering is more important

? What condition (nutrient reserve) were the plants in at purchase

Suggested Readings

Growing Media for Ornamental Plants and Turf. Handrek, K and N. Black. Uni. of New South Wales Press

ISBN 0 86840 333 4

?

Drip

Where does the Nitrogen go ?

63%

1%Substrate

13%Plant

8%Pruning

15%Runoff

13 g N

Plant Uptake Efficiency

21%holly data, 2001

• Both Liquid and CRF

?

Overhead Irrigation

Where does the Nitrogen go ?

69%

1%Substrate

5%Plant

3% Pruning22%

Runoff

33 g N

Plant Uptake

Efficiency8%

Both CRF and Liquid Feed

Holly data, 2001

Take home message – great microbial competitiion for N

Fertility - special situations • Mycorrhizal Symbiosis Fungal infection creates a mutualistic relationship with plant

Very useful to the plant under conditions of low fertility

Fungal mycelia are smaller, have greater surface area than plant roots Potential disease resistance, drought resistance via symbiosis

Ectomycorrhizal and Endomycorrhizal (more common)

Mycorrihzae take C compounds from plant… initially slows growth … eventual long term benefits

High fertility retards rate of infection

N Fertility Recommendations(Turf)

• N Fertilizer plan considerations

– what types of N should be applied– annual N application rates– application timing

N Fertility Recommendations(Turf)

• N Fertilizer - types

– All soluble or mixed with slowly available– nitrate, ammonium or both

– turf uses mainly nitrate (NO3) nitrate taken up within 3 days of application leaching potential high for nitrate should not use in areas that are leaching prone should use a 50% WIN formula

• N Fertilizer – rate issues– how much to apply per application– how much to apply per year

– all soluble – no more than 1 lbs per 1000 sq.ft– nitrate, ammonium or both

– can increase rate if you have S.R. N, but only up to the annual max rate

• N Fertilizer Recommendations

N Fertility Turf Recommendations


Table 1. Nitrogen Recommendations for Commercially Maintained Turfgrass on Sites Total Nitrogen Annually (lbs. N/1000 ft2)

Years 1-2 Subsequent YearsCool Season Grasses

Kentucky bluegrasses

Turf-type tall fescue

Fine fescue

Perennial Ryegrass

3.0 - 4.53.0 - 4.01.0 - 3.03.0 - 4.0

3.0 - 4.02.0 - 3.00.0 - 2.03.0 - 4.0

Warm Season Grasses

Bermudagrass

Zoysiagrass

3.0 - 4.01.0 - 3.0

3.0 - 4.00.0 - 2.0

adjust if mulching or in low traffic areas


Table 2. Recommended Periods for N Fertilization of Turf Areas.

Recommended Periods

Periods to Avoid

Warm Season Grasses

1 month before dormancy breaks through Sept. 1st

September 1st through1 month before dormancy breaks

During severe or prolonged drought

Cool Season Grasses

1 month before top growth starts through early June

Late August through 6 weeks after first killing frost

Mid-June through mid-August

When turf is dormantdue to heat, drought, or cold

• P Fertilizer – rate issues– Unlike N, based on soil test results– P is not needed in large quantities

– before soil test results– no more than 1 lbs P2O5 per 1000 sq.ft

• P Fertilizer Recommendations

P Fertility Turf Recommendations

• Performed at least every 3 years

– Low, Medium, Optimum - Excessive

– the analysis is as good as the sample

– useful tool, different extraction methods

– in Maryland, test results converted to FIV

– gauge P and K fertility on these values

Soil Testing


Table 3. Phosphate Recommendations for Maintenance of Turf Sites Based on FIV Soil Test Results

Low

0-25

Medium

26 - 50

Optimum - Excessive

51-100, >100

2.0 1.0 0.0

FIV Soil Test Categorylbs of P2O5 per 1000 sq/ft

• Performed at least every 3 years– the analysis is as good as the sample

– take at least 15 random cores

– divide area into similar soils, slopes, history

– scrape surface litter, sample 4 inches down

– mix samples in clean bucket

Soil Testing

• Sampling

– fill sample bag 1/3 to 1/2 full

• Interpreting analysis– Converting lab values to FIV

Soil Testing

• Conversion to FIV– conversion depends on Lab– each lab has its own analysis– one value (FIV) is needed for fertility recommendations

Example: A soil-test report from A & L Laboratories contains the following data:

Phosphorus, Bray P1 29 ppm

Soil TestingTo determine an equivalent Maryland FIV value for each soil-test nutrient, multiply the regional laboratory reported value, expressed in the units shown, by the value in column A and then add the value in column B.

86 ppm

P-FIV (86 x 1.69) + 6 = 151


Table 3. Phosphate Recommendations for Maintenance of Turf Sites Based on FIV Soil Test Results

Low

0-25

Medium

26 - 50

Optimum - Excessive

51-100, >100

2.0 1.0 0.0

FIV Soil Test Categorylbs of P2O5 per 1000 sq/ft

55 151

Nitrogen (N)

Deficiency - occurs in oldest leaves first

- stunted growth yellowing, chlorosis, stunted growth, leaf drop, increased root shoot ratio

Symptoms of Deficiency and Toxicity

Toxicity- occurs with ammonium only- yellowing, chlorosis, root death- interactions with K, Ca, Mg

Phosphorus (P)


- older leaves darken and turn purple, leaf margin necrosis, low production of flowers, fruit and seed


Toxicity- mostly interactions with other nutrients including zinc, copper and iron

Potassium (K)

K+

Like phosphorus, potassium exists as many forms in soils, and much of it is unavailable to plants, Plants take up potassium in large amounts compared to other nutrients. Only the demand for nitrogen is greater. In plant tissue the N:K ratio is close to 1:1.

Maintains a variety of plant metabolic activity mainly by regulating water status and stomatal control.

Aides in carbohydrate transport and cellulose production.

Mobile in plant

Potassium (K)


- yellowing of margins and tips of leaves- edge “scorch”


Toxicity- mostly interactions with other nutrients including calcium and magnesium

Sulfer (S)

SO4-2

In soil, the majority of sulfur is found in organic form and to a lesser extent mineral form as sulfates

Plant roots actively take up sulfur primarily as sulfates SO4 -2,

Plants utilize sulfur in amino acids, proteins, vitamins and other plant compounds like glycoside oils that give onions and mustards their characteristic flavors..

Sulfur also activates certain enzyme systems

Not Mobile in plant

Sulfur (S)

Deficiency - occurs in youngest leaves first

- similar to N deficiency


Toxicity- There are rarely issues of toxicity

Calcium (Ca)

Ca 2+

Free calcium is loosely bound to organic and mineral colloids

Calcium is taken up passively in roots tips and moves through the plant primarily via the xylem during evapotranspiration

Mainly found in the cell walls

Not Mobile in plant

Responsible for membrane stability and cell wall integrity

Calcium is required for the extension of cell walls during cell growth at shoot and root tips and enhances pollen tube growth.

Calcium (Ca)

Deficiency - Occurs in youngest leaves first

- Reduction of growth at meristems - Deformed and chlorotic leaves - leag margin necrosis


Toxicity- mostly interactions with other nutrients including magnesium, potassium causing deficiencies

Mg 2+

Magnesium is made available to the plant through exchange with soil colloid complexes

Plants take-up magnesium passively, transported mainly through the phloem

Fifteen to twenty percent of the magnesium in plants is found in the pigment molecule, chlorophyll.

Mobile in plant

Cofactor for enzymes that help transfer energy and CO2 fixation

Magnesium (Mg)

Assists in RNA translation for protein synthesis

Magnesium (Mg)

Deficiency - Deficiency symptoms appear in older leaves as interveinal chlorosis.


Toxicity- There is typically no magnesium toxicity.

Cl -

Chlorine naturally occurs in soils as constituents of many soil minerals and is made available through natural weathering.

Taken actively and passively depending on soil concentrations, active when low and passive when concentrations are high

Utilized in several processes of photosynthesis.

Mobile in plant

Chlorine (Cl)

Chlorine (Cl)

Deficiency - Deficiencies are uncommon


ToxicityYellowing and burning of leaf tips, with interveinal areas being bleached, scorched and necrotic in severe cases.

Fe 2+

Iron is ubiquitous in many soils, yet availability depends on soil chemistry.

Actively taken up by the plant and is transported by xylem to the leaves.

Utilized in several processes of photosynthesis.

Not mobile in plant

Iron (Fe)

Deficiency - Iron deficiency is similar to magnesium deficiency symptoms (interveinal chlorosis), but occurs on youngest leaves first


Toxicity- iron interferes with manganese uptake manganese deficiency (mottled yellowing between veins developing as necrotic lesions later), as.

Iron (Fe)

Mn 2+

Availability depends on pH and organic colloid content. Increased in low pH

In the plant manganese is transported in the xylem and delivered to mertistematic tissue where it is largely immobilized.

Cofactor for many metabolic enzymes and is important factor in photosynthesis. Used to split water.

Not mobile in plant

Manganese (Mn)

Deficiency - Interveinal chlorosis, similar to iron and zinc.


Toxicity- Toxicity varies among species. - Occurs in acid soil conditions when manganese is most available- Dark purple or brown spots within the leaf margins and/or leaf tip necrosis- Toxicity varies among species. Plants associated with acid soils are naturally tolerant to high manganese conc.- Severe toxicity results in stunted and yellowed meristems.

Manganese (Mn)

H3BO3

Availability depends on pH and organic colloid content. Increased in low pH

Boron moves into the plant, passively taken up in solution by the roots via evapotranspiration, moving through xylem

Factor in cell growth, including division, differentiation, and elongation

Not mobile in plant

Boron (B)

Cell processes like carbohydrate metabolism and other metabolic pathways Concentrated at growth areas including reproductive structures.

Deficiency - Since boron is associated with cell growth, deficiencies usually show up in new growth as wrinkled and withered

leaves, with tip death soon after. - Like calcium, deficiencies may be caused by drought or high humidity.


Toxicity- Toxicity can develop quickly, the range between deficient and toxic supply is small.- Different tolerances among plant species. - Yellowing of the leaf tips, interveinal chlorosis and leaf margin scorching.

Boron (B)

Cu 2+

Optimally available in slightly acid conditions where the copper ion exchanges with other cations on soil colloids

Root uptake is active and copper moves in the xylem, complexed with amino acids and other nitrogenous compounds.

Copper is utilized with enzymes for metabolic activities and photosynthesis.

Not mobile in plant

Copper (Cu)

Deficiency - Deficiencies of copper show up on the youngest leaves first - Depressed and twisted growth- New leaves appear pale along the margins but green at the end of the veins. - Spotty necrosis occurs in the leaf margins. Stems may become distorted and twisted.


Toxicity- Toxic levels of cooper induce iron deficiency and accompanying symptoms along with depressed root growth.

Copper (Cu)

MoO4 -2

Molydenum uptake is dependent on solubility of the ion. Unlike many micronutrients, molybdenum becomes more available in higher pH.

In the leaf, used for an important enzymatic process called nitrate reduction, the first of two important physiological steps that make nitrate usable in the plant

Relatively mobile in plant

Molybdenum (Mo)

Deficiency - Since molybdenum is essential for nitrate reduction, a deficiency in molybdenum manifests as a nitrogen deficiency - leaf chlorosis in older leaves- then leaf margin wilting - leaf and meristem death


Toxicity- rare in soils and plants can tolerate relatively high levels of molybdenum

Molybdenum (Mo)

Zn +2

Slightly mobile in plant, mainly stored in roots

Zinc (Zn)

present in sulfide and silicate minerals and is also associated with organic colloids Zinc is actively taken up by plants and transported through the xylem metabolic functions including auxin (growth hormone) production, a cofactor in protein synthesis, enzyme activity and carbohydrate metabolism and regulation. chlorophyll production

may enable plants to tolerate colder temperatures

Deficiency - Symptoms on older leaves first- Include interveinal chlorosis, curled and dwarfed leaves

and then leaf scorch and necrosis.- excessive phosphorus can interfere with zinc uptake


Toxicity- May occur in low pH soils (< pH 5) or where municipal sludge has been added to soils - Toxicity concentrations are species dependent - interfere with iron uptake

Zinc (Zn)

Ni +2

Possibly mobile in plants

Nickel (Ni)

Nickel is the newest recognized essential plant nutrient

requirement was not known because impurities in irrigation water and fertilizers supplied the very low requirements of this nutrient required for the enzyme urease to metabolize urea, releasing the ammoniacal nitrogen for plant use for iron absorption and seeds production and germination evidence to suggest that carbon respiration and nitrogen metabolism are sensitive to Ni nutrition

Deficiency - rounded, blunt and slightly curled leaves known as “mouse-ear” - seen on spring growth and is a result of accumulation of urea to the point of toxicity


Toxicity- At a level of 100 ppm or higher, nickel is considered to be phytotoxic - toxicities typically exist in areas where industrial waste

has been concentrate - In beets severely stunted growth; young leaves at early stage show chlorotic iron deficiency symptoms, followed

by severe necrosis, collapse and death

Nickel (Ni)

Documents

Plant Nutrition Andrew G. Ristvey Wye Research and Education Center Maryland Cooperative Extension College of Agriculture and Natural Resources University