Download - INM Rice (Organic Fert.)
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Organic fertilizers and rice
Roland Buresh
Principal Scientist
Achim Dobermann
Deputy Director General for Research
International Rice Research Institute
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Organic farming and organic fertilizers
are not the same
Organic farming is a form of agriculture that
deliberately follows a set of management
practices
Organic ferti lizer is ferti lizer derived fromanimal or plant materials
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What are organic materials?
Crop residues Stubble and straw
Locally available materials Farmyard manure
Plant biomass Green manures
Compost
Commercially available fertilizers Produced from plant and/or animal
byproducts
Microbial amendments
Materials derived from plants or animals
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Why apply organic materials?
1. Improve soil physical and chemical properties
Water-holding capacity
Soil structure
Nutrient-holding capacity
2. Provide a source of plant-available nutrients
Alternative to mineral fertilizers
3. Enhance biological processes
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What organic material to apply?
1. Improve soil physical and chemical propertiesAdded OM should be retained for long period
Large amount of slow decomposing organic material
High C/N ratio desirable
Surface mulching/no tillage can be desirable
2. Provide a source of plant-available nutrients
Added OM should rapidly release nutrientsLarge amount of fast decomposing organic material
Best materials are high in nutrients & disappear rapidly
Low C/N ratio desirable
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Where to apply organic material?
Lowland riceUpland crop
Til lage of aerated soil Tillage of flooded soil
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Land preparation and flooding for
lowland rice affects soil
Soil structure and
aeration
Important for crop
production
Destroyed by land
preparationSoil microorganisms Aerobes Anaerobes
Mineral matterOrganic matter
Water
Air
Soil with upland
cropLowland rice
soilSoil is about 50% pore
space (air and water) and
50% particles (mineral and
organic matter
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Benefit of organic Upland crop Lowland rice
1. Improve soil physical
and chemical
properties
*** Important
Requires slow
decomposing material
2. Provide a source ofplant-available
nutrients
** Potentially importantRequires fast
decomposing, nutrient-
rich material
3. Enhance biological
processes
** Potentially important
Must overcome a limit to
crop growth
Role and importance of added
organic materials depend upon crop
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Benefit of organic Upland crop Lowland rice
1. Improve soil physical
and chemical
properties
*** Important
Requires slow
decomposing material
Limited importance
Normally not serious
constraint for rice
2. Provide a source ofplant-available
nutrients
**Potentially importantRequires fast
decomposing, nutrient-
rich material
**Potentially importantRequires fast
decomposing, nutrient-rich
material
3. Enhance biological
processes
**Potentially important
Must overcome a limit to
crop growth
* Lesser importance
Normally less serious
constraint for rice
Requires anaerobes
Role and importance of added
organic materials depend upon crop
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Benefit of organic Upland crop Lowland rice1. Improve soil physical
and chemical
properties
2. Provide a source of
plant-available
nutrients
3. Enhance biological
processes
Importance of added organic materials
for upland crop and lowland rice
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Organic materials must decompose in
order to supply nutrients to crops
NH4+
NO3-
HPO4
2-
H2PO4-
K+
SO42-Ca2+
Mg2+
mineralization(microbial activity)
Organic
materials urea NPK
Mineral ferti lizers
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Plants take up nutrients in the same
form from organic and mineralfertilizers
Nutrient Forms absorbed by plant
Nitrogen (N) NH4+, NO3
- ammonium,
nitrate,
Phosphorus (P) HPO42-, H2PO4
- phosphate
Potassium (K) K+ potassium ion
Sulfur (S) SO42-
sulfateCalcium (Ca) Ca2+
Magnesium (Mg) Mg2+
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Example of lowland rice:
Specific conditions:Yield: 6 t/ha at 14%
moisture
Soil P: high-medium
Soil K: high-medium
Rice stubbles retained
Can organic materials match crop
needs for added nutrient?Need for nutrient estimated withNutrient Manager for Rice
Nutrient requirement (kg ha-1)
0
20
40
60
80
100
120
N P2O5 K2O
110
kg/ha
28
kg/ha
31
kg/ha
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Example of lowland rice:
Specific conditions:Yield: 6 t/ha at 14%
moisture
Soil P: high-medium
Soil K: high-medium
Rice stubbles retained
Can organic materials match crop
needs for added nutrient?Supply from addition of 4 t/ha organicwith 1.5% N, 1.5% P2O5, and 1.5% K2O
Nutrient requirement (kg ha-1)
0
20
40
60
80
100
120
N P2O5 K2O
110
kg/ha
28
kg/ha
31
kg/ha
60
kg/ha 30kg/ha
60
kg/ha
The N from organic
material is not sufficientto meet crop needs
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Why use microbial amendments?
1) Hasten decomposition of organic materials
Increase availability of added nutrient
Does not increase total amount of added nutrient2) Increase availability of nutrient in soil
Enable plant to better extract nutrient in soil
Does not increase total amount of nutrient3) Increase supply of N
Symbiotic N2fixation
Associative N2fixation aerobic organism4) Improve crop health
Little or no benefit of added aerobes in lowland rice
Careful agronomic and economic evaluation &quality control are required!
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All aboveground crop residue removed
Long-term continuous cropping experiment
(LTCCE) at IRRI in the Philippines
Started in 1963
3 rice crops peryear
Crop in 2011dry season: 141
The most
intensively
croppedexperimental site
in Asia
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4 N rates, from 0 to high
All plots receive sufficient P, K, and Zn No organic ferti lizer applied
Long-term continuous cropping experiment
(LTCCE) at IRRI in the Philippines
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20
22
24
26
28
1983 1998
Total soil C (g kg-1)
b
a
Organic materials are not essential to maintain
soil organic matter (C) and soil N supply in
lowland rice
Pampolino et al., Soil Sci. Soc. Am. J. (2008)
1983
20
21
22
23
24
1998
Anaerobic N mineralization (mg N kg-1 day-1)
a
a
LTCCE at IRRI, 0-20 cm, avg. of 3 N-fertil ized treatments,
continuous rice
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Addition of organic material does not
guarantee no loss of soil organic matter for
upland crop
Incorporated
crop residue
did not preventloss of soil C in
rice-maize
a
a
b
a
15
17
19
21
23
25Rice-rice
Total soil C (t/ha)
1993
a
a
b
a
Rice-maize
2006 20061993
R. Buresh, IRRI
Long-term experiment at IRRI
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25 LTE in Asia (7 rice-rice, 18 rice-wheat)
Application of either manure or straw did not improve
grain yield trends
Manure or straw may be profitable when (i) available
& affordable and (ii) used as a complement to a
recommended dose of inorganic NPK
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Summary
There are not enough organic nutrient sources to meetneeds to feed this world
Benefits of organic materials for soil physical and
chemical properties are greater for upland crops thanfor lowland rice
Incorporation of crop residue or manure is not
essential for many productive lowland rice soils
Organic materials and crop residues seldom increaselowland rice yield compared to ferti lizer bestmanagement practice
Use organic fertilizer when it is economical, as a
complement to mineral ferti lizers
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Practical considerations for organic
fertilizers
Land, water, energy and time are required to produce
organic materials
Nutrient content can vary widely among materials andbatches of a material
They often do not supply enough N
They might not give short-term benefit on yield
They must have the same product stewardship
regulations as mineral ferti lizers: accurate display ofnutrient content, quality control, proper usage
Subsidies might distort markets