inm rice (organic fert.)

7/30/2019 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


2/22

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


9/22

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


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


10/22

Benefit of organic Upland crop Lowland rice1. Improve soil physical

and chemical

properties

2. Provide a source of

plant-available

nutrients


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

inm rice (organic fert.)

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