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Plant Nutrients

PLANT NUTRIENTS - Review 17 ESSENTIAL NUTRIENTS

Important for GROWTH and DEVELOPMENT

3 ESSENTIAL NUTRIENTS C - Carbon, H - Hydrogen, O – oxygen

14 ESSENTIAL NUTRIENTS come from SOILS 6 – MACRONUTRIENTS 8 – MICRONUTRIENTS

3 BENEFICIAL NUTRIENTS used by some plants Na – Sodium Si - Silicon Co - Cobalt

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PLANT NUTRIENTS 6 - MACRONUTRIENTS

used in LARGE AMOUNTS by plants N > K > Ca > Mg > P > S 3 - PRIMARY MACRONUTRIENTS N – Nitrogen P – Phosphorus K – Potassium Most likely DEFICIENT in soils which limits crop production 3 main FERTILIZER ingredients

PLANT NUTRIENTS 6 - MACRONUTRIENTS

Used in LARGE AMOUNTS by plants N > K > Ca > Mg > P > S 3 - SECONDARY MACRONUTRIENTS

Ca – Calcium Mg – Magnesium S – Sulfur Many soils contain SUFFICIENT quantities Supplied by LIMING and other FERTILIZERS

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PLANT NUTRIENTS 8 – MICRONUTRIENTS (Trace Elements)

Used in SMALL AMOUNTS but still ESSENTIAL

Cu – Copper Cl - Chlorine Fe – Iron Mn – Manganese Mo – Molybdenum Zn – Zinc B – Boron Ni – Nickel (only added recently)

SOIL FERTILITY Presence of ESSENTIAL NUTRIENTS

How do SOILS gain FERTILITY? LIGHTENING and RAIN N – FIXATION DECOMPOSITION of OM WEATHERING of MINERALS FERTILIZING

Or LOSE FERTILITY? HARVESTING CROPS LEACHING of nutrients EROSION of soil TIE-UP of nutrients in FOOD WEB

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SOIL FERTILITY IN CONCLUSION:

GROWING and HARVESTING CROPS takes NUTRIENTS from soils, therefore PLANT GROWTH can SUFFER

By the time we SEE plants suffer, DEFICIENCIES are

severe Understanding NUTRIENTS and DEFICIENCIES are

important to understanding FERTILITY / SOIL TESTING / FERTILIZING

PLANT NUTRITION - N NITROGEN needed in greatest

amounts

PROMOTES SHOOTS DARK, GREEN color (Chlorophyll uses N)

EXCESS SOFT, WEAK GROWTH Prone to DISEASE and INSECTS SLOWS RIPENING and MATURITY DELAYS HARDENING off

DEFICIENCY GENERAL CHLOROSIS yellowing,

OLDER leaves SLOW GROWTH or STUNTING EXTREME SHORTAGE – “FIRING”

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NITROGEN CYCLE 97 - 99% of N is tied up in OM & SOIL BIOLOGY

N - FIXING Bacteria N2 →→→ mineralize NH4+

NITRIFICATION Bacteria 2 NH4

+ + 3O2 →→→ 2NO3- + 8H+

(Acidifiers) Nitrosomonas Nitrobacter

NH4+ →→→→→→ NO2

- →→→→→→ NO3-

(Ammonium) (Nitrite) (Nitrate)

AEROBIC conditions – with O2 Well DRAINED, MOIST soils NEUTRAL pH 6.0 – 7.5 TEMP > 41 degrees

DE-NITRIFICATION Bacteria NO3- →→→ N2 gas

ANAEROBIC conditions – without O2 WATERLOGGED soils

NITROGEN CYCLE N ADDED:

Through LIGHTNING & RAIN

N2 + 2O2 →→→ 2NO2 + H2O →→→ 2HNO3 (Nitrous oxide) (Nitric acid)

N FERTILIZERS – Haber process MANURES Growing LEGUMES

N TAKEN AWAY by:

NO3- ANION and easily leached

NH4+ CATION is ADSORBED so doesn’t leach

Can be lost through VOLATILIZATION

NH4+ + OH- →→→ NH3 + H2O

(Ammonia gas) HARVEST crops EROSION

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PLANT NUTRITION - P PHOSPHORUS

PROMOTES

ROOTS, FLOWERING and FRUITING

BALANCE of N:P

P hastens MATURITY

DEFICIENCY

STUNTING

PURPLE TINT to older leaves and stems

PLANT NUTRITION - P PHOSPHORUS

FORMS Mineral APATITE (Calcium Phosphate) weathers to

Orthophosphate (H2PO4-2)

Secondary Orthophosphate (HPO4-2)

25 - 90% P in OM

AVAILABILITY - Soils have LOTS of P, but most not available (fixed)

pH 3.5 – 4.5 insoluble Iron Phosphate pH 4.0 – 6.5 insoluble Aluminum Phosphate pH 7.0 – 9.0 insoluble Calcium Phosphate

MAX. AVAILABILITY at 6.5 pH (6.0 - 7.0 okay)

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PLANT NUTRITION - P PHOSPHORUS

P is IMMOBILE - No leaching

Can be lost by WIND and WATER EROSION

FERTILIZER PLACED near ROOTS

UPTAKE improved by:

pH CRITICAL (6.0 – 7.0)

good NUTRIENT BALANCE

MYCORRHIZAL associations (better w/low P)

PLANT NUTRITION - K POTASSIUM

PROMOTES TOUGHNESS and

STRENGTH

Regulates stomata

DEFICIENCIES MARGINAL SCORCH (or

yellowing on lower leaves)

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PLANT NUTRITION - K POTASSIUM

FORMS of K Weathering from many MINERALS (Feldspars, Mica)

K+ is a CATION adsorbed by colloids FIXED into certain 2:1 clays

MOVEMENT K MOVES > P, but < N Can LEACH in SANDY SOILS

UPTAKE FASTEST at NEUTRAL pH GREATER K in soil - GREATER UPTAKE

PLANT NUTRITION - Ca CALCIUM

PROMOTES

Part of cell walls

Protein formation

Carbohydrate translocation

DEFICIENCIES LIGHT GREEN color, new leaves

SOFT TISSUE in FRUIT FORMATION “Water Core” & “Bitter pit” in Apples

“Blossom End Rot” in Tomatoes

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PLANT NUTRITION - Ca CALCIUM

FORMS of Ca Weathering from many MINERALS (Feldspars, Limestone,

Gypsum)

Ca+2 is a CATION adsorbed by colloids

MOVEMENT Can LEACH in SANDY SOILS or ACIDIC soils

UPTAKE Excessive K will LIMIT Ca UPTAKE

PLANT NUTRITION - Mg MAGNESIUM

PROMOTES

Essential ingredient in CHLOROPHYLL

DEFICIENCIES

INTERVEINAL CHLOROSIS on older leaves

NECROSIS between veins

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PLANT NUTRITION - Mg MAGNESIUM

FORMS of Mg Weathering from many MINERALS (Limestone, Dolomite lime,

Gypsum) Mg+2 is a CATION adsorbed by colloids

MOVEMENT Can LEACH in SANDY SOILS or ACIDIC soils

UPTAKE Excessive K will LIMIT Mg UPTAKE

PLANT NUTRITION - S SULFUR

PROMOTES Improves STRESS tolerance

DEFICIENCIES LIGHT GREEN on young leaves

STUNTED GROWTH

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PLANT NUTRITION - S SULFUR

FORMS of S Weathering from many SULFATE MINERALS (Gypsum) to SO4

-2

70 - 90% S held in OM

Not ADSORBED or FIXED

MOVEMENT SO4

-2 is readily LEACHED from SANDY or LOW OM soils

PLANT NUTRITION MICRONUTRIENTS

Trace Elements Cu, Cl, Fe, Mn, Mo, Zn, B, & Ni

Needed in VERY SMALL AMOUNTS ENZYMES reused repeatedly

STORED in: SOIL SOLUTION CATION EXCHANGE CHELATES

METAL ion surrounded by a LARGE COMPLEX ORGANIC MOLECULE

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PLANT NUTRITION MICRONUTRIENTS

Iron (Fe)– Deficiency evident in acid loving plants (Ericaceae)

Boron (B) – Deficiency see in crops like strawberries, cauliflower, walnuts, etc.

SOIL pH ACIDIFYING the SOIL

MINERAL SULFUR acidifies soils

2S + 3O2 + 2H2O →→→ 2H2SO4 →→→ 4H+ + 2SO4-2

(Sulfuric Acid)

SULFATE FERTILIZERS can acidify soils

Iron sulfate – Fe2(SO4)3

Aluminum sulfate – Al2(SO4)3

Watch Fe or Al for TOXIC LEVELS

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SOIL SALINITY A problem in ARID REGIONS where

EVAPORATION exceeds PRECIPITATION

SALINE SOILS

HIGH LEVEL of SOLUBLE SALTS ( > 0.2 % salts)

HCl + NaOH →→→ H2O + NaCl (acid) (base) (table salt)

HARD for PLANTS to ABSORB WATER

MEASURED by it’s CONDUCTIVITY

SOIL SALINITY

SODIC SOILS

HIGH in Na SALTS ( > 15% Sodium Carbonate )

Na2CO3 + 2H2O →→→→ 2Na+ + H2CO3 + 2OH- hydrolysis 2Na+ + 2OH- →→→→→→ NaOH

(Lye) LYE raises pH from 8.5 to > 10.0

LIMITS GROWTH of PLANTS by INJURING plant TISSUES

Na results in DESTRUCTION of STRUCTURE

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SOIL SALINITY SALINE - SODIC SOILS

HIGH SALTS and HIGH Na Typically < 8.5 pH

STRUCTURE NORMAL LEACHING of SALTS may cause it to turn into SODIC soil

RECLAIMING SOILS SALINE SOILS

LEACHING with LOW SALT WATER

SODIC or SALINE - SODIC SOILS Add GYPSUM – CaSO4

Ca+2 REPLACES Na+ on SITES →→→ Na2SO4 leaches out