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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
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