作物的营养

Reading for class

• Mineral Nutrition

• Nitrogen and minerals

• Crop residues

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

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

Mineralization Nitrification Denitrification

Nitrogen transformations

NH4+ NO3

-

N20

PlantRoots

NO3- N20 N2

Organic N

N20 N2

Organic N

Runoff

NH3

Fertilizer

Soil minerals

6

6

6

7

3

3

6

2

Hydrolysis = 1 Volatalization = 2; Immobilization and Mineralization = 3; Runoff = 4; Fixation = 5; Denitrification = 6; Leaching = 7

7

5

4 1

3

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

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

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

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

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

Sulphur

• Source:– Contaminant in air and

fertilizers– Sulphates –

ammonium sulphate– Organic matter– Soil minerals

• Not very mobile in the plant

• Important some AA’s, proteins, enzymes Sulphur deficiency

-- older leaves yellow -- poor growth and tillering

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

Critical levels

• Important concept to understand micro-nutrient deficiencies

• Critical levels for micro-nutrients relatively at low concentrations

Nutrient deficiencies

Liebig’s 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.

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 doesn’t distinguish between organic or inorganic.

• Inorganic are usually more concentrated so can provide is less bulk

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

Fertilizer Calculations

• How much 6-24-24 and ammonium nitrate (33.5%N) 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 2.5*6 = 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

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.

Kg N for above ground biomass

Yield kg/ha

Harvest Index Grain

-- N %

Straw

– N %

2t / ha 41 37 35 1.53 0.22

5t / ha 147 113 123 2.10 0.36

8t / ha 283 224 224 2.25 0.55

0.3 0.4 0.5

1 t / ha is about 15-16 bushels per acre

Extra Nitrogen needed for high yields

Nitrogen recovery percentage

Yield kg/ha 50 65 80

5,000 180 138 112

6,000 264 203 165

7,000 330 254 206

8,000 408 314 255

Assumes the soil provides enough nitrogen for a 2,000 kg/ha yield or 42 kgN/haPlus a harvest index of 0.4

Nitrogen contents in above ground parts of wheat by yield

Yield

Kg/ha

KgN/ha

in straw

KgN/ha

in grain

KgN /ha in above ground

1500 22 7 29

2000 31 11 42

2500 40 15 55

3000 50 19 69

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

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

Plant sensitivity to soil pH

Soil pH

4.5-5.5 5.5-6.5 6.5-7.5

Azalea Barley Alfalfa

Bent grass Bean Apple

Blueberry Carrot Sugar beet

Cranberry Maize Asparagus

Dandelion Fescue Broccoli

Fescue Oat Cabbage

Potato Pea Cauliflower

Rhubarb Rye Celery

Sweet potato Tobacco Soybean

Tea Wheat Sweet clover

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

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

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

Sands Sandy loams

Loams Silt loams

Silty clay loams

Initial pH

Tons lime per acre

5.0-5.1 2.5 5.5 8.5 12.0

5.2-5.3 2.0 4.5 6.5 8.0

5.4-5.5 1.5 3.0 4.0 6.0

5.6-5.7 1.0 2.0 3.0 5.5

5.8-5.9 0.8 1.8 2.5 3.5

6.0-6.1 0.6 1.5 2.0 3.0

6.2-6.3 0.5 1.0 1.5 2.5

6.4-6.5 0.3 0.8 1.3 2.0

6.6-6.7 0.2 0.7 1.0 1.5

Nitrogen fixing bacteria

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

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

• Thank you!