Crop Nutrition

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Crop Nutrition

• CSS 311

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Reading for class

• Gardner Ch 5 Mineral Nutrition
• Tesar Ch 7 Nitrogen and minerals
• Stoskopf (85) Ch 11 Crop residues

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Essential Plant Minerals

• 16 essential elements
• C, H, O air and water, photosynthesis
• P, K, S, -- major elements
• Ca, Mg lime elements
• Fe, Mn, B, Mo, Zn, Cu, Cl, Na micro or minor
  elements
• I and Co important for animals

4
Nitrogen

• Sources
• Soil Organic Matter (5 N) soil supplying
  capacity SOM
• Fertilizers
• urea 46-0-0
• Ammonium sulphate 20-0-0 sulphur
• Manures (compost) external inputs

NH4
NO2-
SOM
NO3-
N2O
N2
Roots
Roots
Nitrification
Denitrification
Mineralization
5
Nitrogen transformations
Hydrolysis 1 Volatalization 2 Immobilization
and Mineralization 3 Runoff 4 Fixation 5
Denitrification 6 Leaching 7
N20
N20
N2
Fertilizer
2
NH3
1
6
4
NO3-
Runoff
NH4
3
6
Organic N
Plant Roots
5
3
6
Soil minerals
Organic N
6
NO3-
N20
N2
3
7
7
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Nitrogen

• 78 in the air
• Rhizobial bacteria associations with roots
  legumes and greenmanures
• Mobile element easily leached
• Important for amino acids, proteins and many
  enzymes, hormones and other biochemicals

Nitrogen deficiency -- yellowing older leaves
-- stunted, poor tillering -- earlier maturity
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Phosphorus

• Source
• Soil minerals to soluble phosphatic acids
• External inputs
• Triple super phosphate 0-46-0
• Diammonium phosphate 16-46-0
• Nitrophos 20-20-0
• Rock phosphate slow release
• Organic phosphates released from SOM

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Phosphorus

• P - Fixation in soils an immobile element
• P - placement and banding
• Important in nucleic acids (RNA and DNA),
  proteins, phospholipids, ATP (energy)

Phosphorus deficiency -- dark green to red --
late, irregular maturity
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Potassium

• Source
• Clay minerals NYS soils high illite, so rarely
  deficient
• External inputs
• Potassium Chloride 0-0-60
• Complex or complete 10-10-10 etc.
• Manures and composts

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Potassium

• Partly mobile and can be leached
• Accumulates in growing tissue
• Activates enzyme systems
• Important in translocation sugars but role not
  precisely known
• Mobile in the plant
• Luxury accumulation

Potassium deficiency -- leaf tip burning,
necrosis -- shrivelled seeds -- poor growth
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Sulphur

• Source
• Contaminant in air and fertilizers
• Sulphates ammonium sulphate
• Organic matter
• Soil minerals
• Not very mobile in the plant
• Important some AAs, proteins, enzymes

Sulphur deficiency -- older leaves yellow --
poor growth and tillering
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Other elements

• Calcium cell wall, membranes, cell division,
  enzymes, pH adjustment
• Magnesium chorophyll, catalyst for enzymes
• Iron enzymes, Photosynthesis, heme proteins
• Boron carbohydrate translocation, sterility
• Manganese -- enzymes
• Copper -- enzymes
• Zinc -- enzymes
• Molybdenum nitrogen fixation, enzymes

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Critical levels

• Important concept to understand micro-nutrient
  deficiencies
• Critical levels for micro-nutrients relatively at
  low concentrations

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Nutrient deficiencies
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Liebigs Law of the minimum
Justus Von Liebig 1803-1873
Two books, Organic Chemistry an its Application
to Agriculture and Physiology, and Organic
Chemistry in its Application to Physiology and
Pathology, published in 1840 and 1842
respectively, revolutionized food production.
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Fertilizer

• Means to supply plants with essential nutrients
  in addition to that supplied by the soil
• Organic manure, composts, greenmanures
• Inorganic many different types available
• Plant really doesnt distinguish between organic
  or inorganic.
• Inorganic are usually more concentrated so can
  provide is less bulk

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Fertilizer Definitions

• Complete fertilizer usually contains N-P and K
• Compound fertilizer one formulated to give a
  ratio N-P-K eg. 10-10-10
• Fertilizer ratio ratio N, P205, and K20 so
  10-10-10 would have 10 of these elements
• Premium fertilizer a fertilizer usually
  containing micro-nutrients

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Fertilizer Calculations

• How much 6-24-24 and ammonium nitrate (33.5N) is
  needed to fertilize a corn crop at 120-60-60 kg /
  ha. 50 kg bags
• Answer
• 100 kg bag of fertilizer provides 6-24-24 kg of
  the three elements. Or 33.5 kg N if ammonium
  nitrate
• To get 60 kg P205 and K20 you need 60/24 bags
  2.5 of 6-24-24 or 250 kg of fertilizer
• That provides 2.56 15 units of N
• So need (120-15)/33.5 3.13 bags or 313 kg of
  ammonium nitrate
• Apply all this evenly over 1 hectare of land

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Fertilizer issues

• Cost and availability
• Cost of application
• Need to include energy costs to produce
• Problems of groundwater pollution
• Need to improve efficiency of use
• In developing nations a lot of organic fertilizer
  is burnt to cook food.

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Kg N for above ground biomass
0.3
0.4
0.5
1 t / ha is about 15-16 bushels per acre
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Extra Nitrogen needed for high yields
Assumes the soil provides enough nitrogen for a
2,000 kg/ha yield or 42 kgN/ha Plus a harvest
index of 0.4
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Nitrogen contents in above ground parts of wheat
by yield
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N-use efficiency

• Need to improve the efficiency of external
  nitrogen applied
• Splitting
• Placement
• Slow release
• Nitrification inhibitors
• Increase the soil supplying capacity
• Microbial activity
• Increase SOM -- compost, greenmanures, residues

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Nutrients and pH

• Each element has an optimum pH for availability
  and non-availability
• Most elements available between pH 6 to 7
• Liming can be used to adjust pH if soil is acidic

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Plant sensitivity to soil pH
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Lime requirement(pages 30-42 in CFCSH)

• A means to adjust soil pH when soil is acid
  below pH 6.3. Plants prefer pH 6.4-7.5 most
  nutrients available at that pH
• Lime requirement based on soil tests
• Plants differ in their sensitivity to pH some
  prefer acidic, others alkaline and most prefer
  neutral
• Lime materials vary from limestones to hydrated
  lime. Compared using the term total neutralizing
  value or the ability of the lime to neutralize
  acids.
• Limestone not only supplies calcium but also some
  magnesium and neutralizes acids

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Lime requirement

• TNV of 78 means 100 pounds of limestone can
  neutralize the same amount of acid as 78 pounds
  of pure calcium carbonate.
• Lime must first dissolve in soil solution before
  it can react affected by particle size the
  finer the faster to dissolve
• The term effective neutralizing value (ENV) is
  related to TNV and particle size.
• It is the fraction of the limestone, expressed as
  pure calcium carbonate, that is expected to react
  in the first year of application

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Lime

• Takes time to react
• Must be incorporated into the root zone assumes
  an 8 inch plow layer
• Soil test will determine how much to apply
• Depends on soil texture

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Nitrogen fixing bacteria

• Symbiotic association with rhizobium bacteria
• Species specific need to innoculate
• Soil pH, drainage, temperature important

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Nitrogen fixation

• Mainly found in the legume family
• Can result in a positive addition to soil
  nitrogen but
• Not if you remove all the seed and above ground
  parts then it will be negative
• Greenmanures an effective way to supply nitrogen
  but..
• Break down very fast and results in a flush of
  nitrate that can be leached