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2015/6/9
1
Management practices of fertilization
for improving crop production and
creating safe environment
Jen-Hshuan Chen
Professor and Chair of the
Department of Soil and
Environmental Sciences, NCHU
Thanks
Food & Fertilizers Technology Center (FFTC)
Taichung District Agricultural Research and Extension Station, Council of Agriculture
2015/6/9
2
Jen-Hshuan Chen
Education: PhD, Department of Agronomy, Purdue University, USA (1989)
Position: Professor and Chair,
Department of Soil and Environmental Sciences,
National Chung-Hsing University. Taiwan, ROC
Major field: Fertilizer and Soil Fertility, Soil Management, Agricultural Waste Treatment
Introduction
Fertilizers have sustained world
agriculture and global population .
However, lacking, imbalanced,
inappropriate or excessive use of
nutrients in agricultural systems remains
a concern.
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Traditional fertilization usually focused on
improving the growth and/or the quality
of crops and ignored the possible risk of
negative impact on soil and environment.
Introduction
Essential Nutrients
The plant cannot complete its life cycle
without these nutrients.
The nutrient’s function cannot be replaced
by another nutrient.
The nutrient is directly involved in the plant’s
growth and reproduction.
Most plants need these nutrients to survive.
Nutrients must be available not only in sufficient
amounts but also in appropriate ratios.
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Element Chemical symbol Form(s) taken up by plant
Carbon C CO2
Hydrogen H H2O
Oxygen O H2O , O2
Nitrogen N NH4+ , NO3
-
Phosphorus P H2PO4- , HPO4
2-
Potassium K K+
Calcium Ca Ca2+
Magnesium Mg Mg2+
Sulfur S SO42-
Nutrients essential to plant growth- Macronutrients
Element Chemical symbol Form(s) taken up by plant
Iron Fe Fe2+ , Fe3+
Zinc Zn Zn2+ , Zn(OH)2
Manganese Mn Mn2+
Copper Cu Cu2+
Boron B B(OH)3
Molybdenum Mo MoO42-
Chlorine Cl Cl-
Nutrients essential to plant growth- Micronutrients
0
0
0
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Essential nutrients for plants and animals
Major Elements Micronutrients
Plants and Animals
Calcium (Ca), Carbon (C)
Hydrogen (H), Magnesium (Mg)
Nitrogen (N), Oxygen (O)
Phosphorus (P), Sulfur (S)
Chlorine (Cl), Copper (Cu), Iron (Fe), Manganese (Mn), Molybdenum (Mo)
Plants only
Boron (B)
Animals only
Healthy plant
Healthy life
Arsenic (As), Chromium (Cr), Fluorine (F), Iodine (I), Nickel (Ni), Selenium (Se), Vanadium (V)
Effect of increasing the supply of a nutrient on
crop yield
Amount of nutrient
Yie
ld
1. Ideal conditions
2. Best field conditions
3. Poor field conditions
A A C A
B D
x
y
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Liebig's
law of minimum (Barrel theory)
Increasing the amount of
plentiful nutrients did not increase plant
growth. Only by increasing the amount of the
limiting nutrient (the one most scarce in
relation to "need") was the growth of a plant
or crop improved.
The use of fertilizer improves crop
performance, but at some point, adding
increasingly more fertilizer improves
the yield by less per unit of fertilizer,
and excessive quantities can even
reduce the yield.
Law of diminishing returns
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Fertilizer efficiency
N fertilizer:Flood field:30 ~ 40 %
Dry field:50 ~ 70%
P fertilizer:5 ~ 20 %
K fertilizer:40 ~ 60 %
Pathways of loss:
N: denitrification, ammonium volatilization, leaching, soil erosion, fixation
P: fixation, soil erosion leaching,
K:leaching, soil erosion, fixation
Problems caused by fertilizer abuse
1. Harmful effects on human health
2. Harmful effects on environment
3. Reduced soil quality
(1) Acidification
(2) Accumulation of toxic elements
(3) Accumulation of salt
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Problems caused by fertilizer abuse
4. Contribution to climate change and air
pollution
5. Harmful on plant growth
(1) Diminished plant health
(2) Attract pests and diseases
Harmful effects on human health
Nitrates (NO3-)can contaminate drinking water, which
causes a baby's face to turn blue from a lack of oxygen
in the blood. This is known as methemoglobinemia
(Methemoglobin is a form of hemoglobin that contains
ferric [Fe3+] iron and has a decreased ability to bind
oxygen.)
Farmers and workers exposed to fertilizers over long
periods of time exhibit symptoms of neurological
damage, including dizziness, and headaches.
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Harmful effects on the
environment
When excessive amounts of phosphorus enter
lakes and streams, it stimulates the growth of
algae and other aquatic microorganisms.
eutrophication
Eutrophication
Results “Off flavor” drinking water Reduces water quality Lowers oxygen levels Causes reduction and shifts in aquatic populations
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Reduction of soil quality by fertilizer abuse
Decrease of soil organic matter
Detriment to soil structure
Salinization(salt accumulation)
Acidification
Heavy metal accumulation
Abuse of fertilizer
Poor management
Contribution to climate change
and air pollution
Over fertilization of nitrogen to paddy soils
or soils with poor drainage can contribute to
the release of greenhouse gases such as
carbon dioxide(CO2), methane(CH4) and
nitrous oxide(N2O).
Excess greenhouse gases trapped in the
atmosphere may be contributing to the
increase of land and ocean surface
temperatures.
Causes storms, floods, heat, air pollutants,
shortage of food supply
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Harmful on plant growth
(1) Diminished plant health
Over-application of fertilizer to plants may damage the
plant and reduce crop yield.
Over fertilization often causes root burn due to the
roots of plants which suffer damage from excess salt.
(2) Attract pests and diseases Plants that produce greener, more lush leaves because
of over fertilization may attract more pests. Overuse
of fertilizers stress plants, increasing their susceptibility
to various diseases and insect pests.
Best management Practices of
fertilization (Colorado Legislature,
1990)
1. Improve fertilizer efficiency。
2. Improve or maintain crop yield
and quality。
3. Less impact on soil and
environment。
The act calls for education and training of
all producers and farmers in the proper
use of pesticides and fertilizers.
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4R , BMP of fertilizer (IFA)
Apply the “Right Rate” of fertilizer to match
nutrient supply with crop requirements;
Apply fertilizer at the “Right Time” so nutrients will
be available when crop demand is high;
Apply fertilizer in the “Right Place” or location
where the crop can access the nutrients most
effectively;
Use the “Right Form” of fertilizers that are in or are
easily converted over to compounds best used by the
target crop.
Right Product(s)/ Source(s)
Right Rate
Right Time
Right Place
Balanced fertilization (N, P, K, secondary and micronutrients)
Nutrient form (urea, nitrate, ammonium)
Soil testing
Yield goal
analysis
Crop removal balance
Plant tissue analysis
Crop inspection
Record keeping
Application
timing
Slow- and controlled-release
Fertilizers
Urease and nitrification inhibitors
Application
method
Incorporation of fertilizer
Applicator maintenance and calibration
Examples of elements of FBMPs (IFA, 2009)
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The use of chemical fertilizers, organic
fertilizers or biofertilizers, has its advantages
and disadvantages on nutrient supply, crop
growth and environmental quality.
These advantages need to be integrated in
order to get the most out of each type of
fertilizer, and achieve the balanced nutrient
management for crop growth.
Chemical fertilization
Advantages
Impressive yield increase
Supply nutrients in water-soluble form to ensure rapid availability to crop.
Relative high in nutrient content, only relative small amounts are required for crop growth.
The price is lower than organic fertilizer, and more accepted by farmers.
Disadvantages
Availability of nutrients
decline fast.
Nutrients are easily lost from soil.
Over application will easily happen, thus causing some negative effects, such as reducing soil fertility, polluting water resource, destroying microbes and friendly insects…etc.
Reduces or inhibits soil biological activity
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Organic fertilization
Advantages
Nutrient supply is more
balanced.
Enhance soil biological activity and encourage the growth of beneficial microorganisms.
Increase OM content of soil, and improve soil physical, chemical and biological properties.
Enhance root growth due to better soil condition.
Disadvantages
Comparative low in
nutrient content.
Too low nutrients release rate to meet crop requirement in a short time.
Highly variable nutrient composition and cost is higher.
Long-term and/or heavy application may result in salts, nutrients and heavy metals accumulation.
Biofertilizers
Rhizobia
Azotobacter, Azospirillum
Phosphate-Solubilizing bacteria
Vescular arbuscular mycorrhizae, VAM
Potassium-Solubilizing bacteria
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Biofertilizer usuage
Advantages
Stimulate plant growth
Help plant to against adverse environmental stress
Improves water and nutrients absorption by plant from the soil.
Reduce the use of chemical fertilizer.
Reduce plant disease.
Disadvantages
Does not directly supply
any nutrient to crop.
Some need specific host, eg. rhizobia
Strict usage environment and storage condition
Short shelf life, lack of suitable carrier materials, susceptible to high temperature, salt accumulation, excess fertilizer addition , and waterlogging.
Quality stability problem.
Right Placement
Correct placement of fertilizers in the
plant rooting zone often improves the
efficiency of nutrient uptake by plants and
consequently encourages maximum
yields of crops.
Maximizing crop uptake also reduces the
potential for losses of nutrients.
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Methods of application: Broadcast
Broadcast is generally preferred for
plants that are actively growing over
most (or all) of the soil surface, such as
pastures, alfalfa, clovers.
Broadcast applications generally are less
efficient and leave more P at the soil
surface than banding.
Methods of application: Band
For row crops, banding is generally the most
efficient method for applying micronutrient
fertilizers.
Banded applications below seeding depth,
placement with the seed and/or broadcast-
incorporated applications are superior to
surface broadcast treatments because they
minimize losses of phosphorus.
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Methods of application: Fertigation
Fertigation is the application of
water-soluble fertilizers by injecting
fertilizer into irrigation water.
Advantages
Saves fertilizers
Saves water
Improves crop growth and quality
Fertilizers are applied directly to leaves. The
method is almost invariably used to apply
water-soluble straight fertilizers and used
especially for high value crops such as fruits.
Foliar applications of macronutrients are
generally not cost effective because plants’
requirements for macronutrients are greater
than the amount that can be taken up
through the plant leaves.
Methods of application: Foliar
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Under which conditions should we
use foliar feeding?
Limiting conditions - A foliar feeding is
recommended when environmental conditions limit the
uptake of nutrients by roots. This include temperature ,
water stress, root disease etc.
Nutrient deficiency symptoms - One of the
advantages of foliar feeding is the quick response of the
plant to the nutrient application.
In specific growth stages – Plants require
different amounts of nutrients in different growth stages.
Foliar applications of essential nutrients during key
stages can improve yield and quality.
Right time — match the nutrient
requirement of crop (Splitting application)
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Erosion control BMPs for reducing surface losses
of phosphorus from crop fields
Conservation tillage
Cropping system that maintains at least 30% of
the soil surface covered with residues after
planting
Conservation cover
Perennial vegetative cover established and
maintained on highly erodible lands where
other BMPs are insufficient to reduce adverse
water quality impacts
Grass filter strip
Permanent sod strip planted at the base of sloping fields or in between the field and surface water bodies
Contour farming
Crops planted on the natural contour of the land to reduce P loss
國立中興大學土壤環境科學系
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Phosphorus BMPs
Sample the tillage layer of soil in each field on a regular basis and have soil analyzed to determine available soil P levels prior to applying P fertilizer.
Credit all available P from manures and other organic residues to the P requirement for the crop.
(Waskom, 1994)
Fertilize soils with ‘low’ to ‘medium’ P soil test values using environmentally friendly and economically sound agronomic guidelines.
In general, soils testing ‘high’ will not respond to additional P and should not receive fertilizer unless a banded starter is needed to compensate for low soil temperatures.
Phosphorus fertilizer should not be applied to soils testing ‘very high’ for soil P.
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When erosion potential is severe, install
structures such as diversions, terraces,
grass waterways, filter fences, and
sediment basins.
Maintain a buffer strip (where fertilizer
and manure is not applied) a safe distance
from surface water and drainage
channels.
Divide large, non- uniform fields into smaller
fertility management units based upon yield
potential or soil type and fertilize according to P
levels determined through soil analysis.
Apply P fertilizers where they can be most
efficiently taken up by the crop. Band application
of P in the root zone reduces surface loss potential
and enhances nutrient availability, especially in
cold or P deficient soils.
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Incorporate surface applied P into the soil
where any potential for surface runoff or erosion exists.
Minimize soil erosion and corresponding P losses by establishing permanent vegetative cover, conservation tillage and residue management, contour farming, strip cropping, and other management practices as feasible.
Maintain grass filter strips on the downhill perimeter of erosive crop fields to catch and filter P in surface runoff.
Manage irrigation water to minimize runoff and erosion.