Rice

Nutrient Management

Principles of Nutrient Management Fertiliser Application Major Nutrients (Nitrogen) Sources of Nitrogen Phosphorus Sources of Phosphorus Potassium Sources of Potassium Biofertilizers for Rice Method Of Application Of Biofertilizers SSNM Irrigated Rice Green Manures

Principles of Nutrient Management

  • To provide nutrients to crop plants in required quantities
  • Climate (tropical/temperate)
  • Type of crop (legume/non-legume)
  • Season (kuruvai/thaladi/samba)
  • Type of soil (Texturally, fertility status)
  • In available form: Readily available, Slowly available,Fixed in the soil
  • At right time:Critical phase for nutrient
  • Type of fertilizer/manure
  • By right method
  • Mobility of nutrient
  • Type of nutrient (Macro/micro, soil/plant)
  • Loss of nutrient (Volatilization/leaching)

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Fertiliser Application

First apply 12.5 t of FYM or compost or green leaf manure @ 6.25 t/ha. Instead of green manure, press-mud / composted coir-pith can also be used.

Apply fertilizers as per soil test recommendations.
If soil test recommendation is not adopted, follow blanket recommendation

Particulars
Fertilizers (kg/ha)
N
P
K
Short duration varieties
a. Cauvery delta and Coimbatore tract
150
50
50
b. Other tracts

120

40

40

Medium and long duration varieties

150

50

50

Hybrids

175

60

60


In this above recommendation N and K are applied in four equal splits viz., basal, tillering, panicle initiation and heading stages.
Tillering and Panicle initiation periods are crucial and care should be taken to provide the full recommended dosage.

The entire P may be applied as basal dose. When the green manure is applied, rock phosphate can be used as a cheap source of P fertilizer. If rock phosphate is applied, the succeeding rice crop need not be supplied with P. Application of rock phosphate + single super phosphate or DAP mixed in different proportions (75:25 or 50:50) is equally effective as SSP or DAP alone.

Basal dose

Particulars
Fertilizers (kg/ha)
N
P
K
Short duration varieties
a. Cauvery delta and Coimbatore tract
37.5
50
12.5
b. Other tracts

30

40

10

Medium and long duration varieties

37.5

50

12.5

Hybrids

43.75

60

15


Top dressing

Stages
Short (105)
Medium (135) and Long (150)
Hybrids
Cauvery delta and Coimbatore tract
Other tracts
N
K
N
K
N
K
N
K
Tillering
37.5
12.5
30
10
37.5
12.5
43.75
15
Panicle Initiation
37.5
12.5
30
10
37.5
12.5
43.75
15
Heading
37.5
12.5
30
10
37.5
12.5
43.75
15

DAS -Days after Sowing

Dosage in Kgs/ Ha

To apply the recommended dose of fertilizers follow the conversion table given below :

N x 2.17 = Urea

P x 6.25 = Super phosphate

K x 1.65 = Murate of potash

Foliar nutrition in Rainfed rice

Foliar spray of DAP 2% + urea 1% + KCL 1% at active tillering and panicle initiation stages along with the full recommend dose of NPK for pre monsoon dry seeded rainfed rice for higher yields and net returns.

Application of zinc sulphate

Apply 25 kg of zinc sulphate mixed with 50 kg dry sand just before transplanting. It is enough to apply 12.5 kg zinc sulphate /ha, if green manure (6.25 t/ha) or enriched FYM, is applied.

If deficiency symptom appears, foliar application of 0.5% Zinc sulphate + 1.0% urea can be given at 15 days interval until the Zn deficiency symptoms disappear.

Application of gypsum

Apply Gypsum @500kg/ha (as source of Ca and S nutrients) during last ploughing.

Site-Specific Nutrient Management

Now increasingly Site-Specific Nutrient Management is recommended for all parts of Tamilnadu.

The SSNM is a generic approach tailored to the site-specific conditions of a recommendation region. Fertilizer requirements are then calculated based on the plant nutrient requirement considering the soil indigenous nutrient supply. Simple tools such as leaf color chart (LCC) help for detecting plant nitrogen deficiencies within a season allowing real-time adjustment of nitrogen management.

When the nutrients application through SSNM is optimized and well timed it minimizes the ill effects of interaction of major nutrients thereby achieving the targeted yields with reduced pest incidence.

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Major Nutrients

Nitrogen

  • Most limiting nutrient
  • Highly soluble and highly mobile
  • Rapid transformation into leachable forms
  • Losses may be as a gas (volatalisation) when nitrate is exposed to anaerobic condition and leaching
  • N loss is very high in flooded soils

Role of N in plant system

  • Green colour of plant (photosynthesis)
  • Rapid vegetative growth (height, tillering, branching)


  • Increased leaf size (more leaf area and high radiation use efficiency)
  • Increased protein content of grain (% N x 6.25 = % Protein)

Deficiency symptoms

  • Plant become stunted and yellow in appearance first on lower surface
  • Leaves will turn brown and die in case of severe deficiency
  • Deficiency starts first at the leaf tip and progress along the midrib
  • Reduction in yield

Injury due to excess N – Fertilizer

  • Leads to other nutritional problems
  • Increased pest and disease incidence
  • Dark green leaves
  • Lodging of crop due to excess growth
  • Increased chaffy grains.

Leaf Colour Chart (LCC) based nitrogen management

Leaf Colour Chart (LCC) based nitrogen management in transplanted and direct (Drum) seeded wet land rice is a need based N application Method.

This method will be useful to avoid excess or deficit N application and there by wastage can be prevented.

Details

Leaf Colour Chart (LCC) measures the green colour intensity of rice leaves. The chart consists of six colour strips - from light yellowish green (No.1) to dark green (No.6). The topmost fully expanded leaf is chosen for leaf colour measurement as it is highly related to the N status of rice plants. The colour of a single leaf is measured by holding the LCC vertically and placing the middle part of the leaf 1cm in front of a color strip for the LCC vertically and placing the middle part of the leaf 1cm in front of a color strip for comparison. During measurement, always shade the leaf being measured with your body. Every time same person should take leaf colour measurements at the same time of the day. Take readings of ten leaves at random for each field to determine the need for N topdressing. LCC readings are normally taken once in a week, starting from 14 days after transplanting (DAT) for transplanted rice; and 21 days after seedling (DAS) for wetseeded rice. If six or more leaves read below the specified threshold value, one top dressing of N has to be done. If the value is above the threshold value, there is no need for top dressing during that week.

Benefits

  • Simple and easy to use by farmers.
  • Cheaper cost
  • Promote need based N application based on soil N supply and crop demand
  • To determine the time of N top dressing to rice
  • Saving of about 20-40kg N ha -1
  • N use efficiency is high

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Sources of Nitrogen

Organic sources

Material
Nitrogen (N) (per cent)
Farm yard manure
0.5 - 1.5
Compost (Urban)
1.0 - 2.0
Compost (Rural)
0.4 - 0.8
Green manure’s
0.5 - 0.7
Non-edible cakes
Castor cake
5.5 - 5.8
Cotton seedcake (undecorticated)
3.9 - 4.0
Mahua cake
2.5 - 2.6
Karanj cake
3.9 - 4.0
Neem cake
5.2 - 5.3
Safflower cake (undecorticated)
4.8 - 4.9

Inorganic fertilizers

Name of the fertilizer
N%
Urea
44.0-46.0
Ammonium sulphate
19.9-20.0
Ammonium sulphate, Calcium nitrate
26.0
Ammonium nitrate
25.0
Ammonium chloride
25.0
Calcium nitrate
13.0-15.0
Sodium nitrate
16.0
Calcium cyanamid
21.0
Anhydrous ammonium
82.0
Ammonium nitrate
32.0-35.0

Compound fertilizers

Particulars
Compound fertilizers
N
P
K
Diammonium phosphate
18
46
0
Urea
28
28
0
Ammonium phosphate (Gromor)
20
20
0
Co (NH2)2 (NH4) HPO4
24
24
0

Increasing nitrogen use efficiency by treating urea

  • To increase the nitrogen use efficiency urea can be treated with neem and coal tar.

Neem treated urea:

  • Blend the urea with crushed neem seed or neem cake 20% by weight. Powder neem cake to pass through 2mm sieve before mixing with urea. Keep it overnight before use.
  • Mixing of urea with gypsum and neem cake at 5:4:1 ratio will also increase the nitrogen use efficiency.

Coal - Tar treated urea

  • For treating 100 kg urea, take one kg coal-tar and 1.5 litres of kerosene.
  • Melt coal-tar over a low flame and dissolve it in kerosene. Mix urea with the solution thoroughly in a plastic container, using a stick. Allow it to dry in shade on a polythene sheet.
  • This can be stored for a month and used for basal application.

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Phosphorus

  • Immobile
  • Limiting nutrient – Limited availability
  • Negligible / No loss
  • Most of P fixed in soil

Role of P in plant system

  • Stimulates growth and development of roots
  • Promotes early flowering and ripening (late planted crop comes to harvest in time)

  • Encourages tillering
  • Helps overcome adverse conditions in early stages of crop growth

Deficiency symptoms

  • Stunted growth
  • Poor tillering/branching
  • Poor root growth

Injury due to excess P application

  • Fixed in soil – not available to plants
  • Leads to Zinc deficiency

Application of phosphorus to the nursery has the following advantages

  • Seedlings absorb and store P and utilize it at a later stage
  • Higher yield
  • Nursery application highly economical

Phosphorous for Rainfed Rice

Skipping basal application of P and application of P through DAP on 20-25 days after germination at the time of weeding in rainfed direct sown rice as an alternative P management practices.

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Sources of Phosphorus

Organic manures

Material
Phosphate (P2O5) %
Farm yard manure 0.4-0.8
Compost (Urban) 1.0
Compost (Rural) 0.3-0.6
Green manure’s 0.1-0.2
Non-edible cakes
Castor cake 1.8-1.9
Cotton seedcake (undecorticated) 1.8-1.9
Mahua cake 0.8-0.9
Karanj cake 0.9-1.0
Neem cake 1.0-1.0
Safflower cake (undecorticated) 1.4-1.5

Inorganic fertilizers

Name of the fertilizer
Phosphatic fertilizers
-
P2O5 %
-
Super phosphate (single)
-
16.0-20.0
-
Super phosphate (Double)
-
30.0-35.0
-
Super phosphate (Triple)
-
45.0-50.0
-
Basic slag
-
3.0-8.0
-
Mussori
-
23.0-24.0
-
Purulia
-
23.0
-

Compounds fertilizers

Particulars
Compound fertilizers
N
P
K
Diammonium phosphate (SPIC)
18
46
0
Urea
28
28
0
Ammonium phosphate (Gromor)
20
20
0
Co (NH2)2 (NH4) HPO4
24
24
0
NPK(IFFCO)
10
26
26
(MFL)
17
17
17
(RCF)
15
15
15
(ZACL)
19
19
19
(CFL)
14
35
14

 

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Potassium

  • Majority of soils are rich in potassium
  • Mobility is less than N and more than P
  • K requirement is slightly lesser in rainy season compared to dry season
  • Excess quantities of hydrogen sulphide, organic acids, carbondioxide and iron retards potassium uptake
  • Excess Na and Ca in soil retards K absorption

Role in plant system

  • Involves in working of enzymes
  • Helps in production and movement of photosynthates to sink
  • Helps in proper uptake of other nutrients
  • Influences tillering or branching of plant
  • Influences size and weight of grain
  • Induces tolerance in plant against stress (biotic and abiotic)
  • Makes the plant tolerant to pests and diseases
  • Reduces adverse effects of unfavourable climatic conditions

Deficiency symptoms

  • Bluish green leaves – when young
  • Older leaves- irregular Chlorotic and necrotic areas
  • Poor grain formation
  • Weak stem leads to lodging

Injury due to excess K application

  • Leads to calcium magnesium and iron deficiencies.

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Sources of Potassium

Organic manures

Material
Potash (K2O) (Per cent)
Farm yard manure
0.5-1.9
Compost (Urban)
1.5
Compost (Rural)
0.7-1.0
Green manure’s
0.6-0.8
Non-edible cakes
Castor cake
1.0-1.1
Cotton seedcake (undecorticated)
1.6-1.7
Mahua cake
1.8-1.9
Karanj cake
1.3-1.4
Neem cake
1.4-1.5
Safflower cake (undecorticated)
1.2-1.3

Inorganic fertilizers

Material
Potassic fertilizers
N
P
K
Muriate of potash (KCL)
-
-
50.0-60.0
Potassium sulphate
-
-
48.0-52.0
Potassium phosphate
-
-
30.0-50.0

Complex fertilizers

Particulars
Complex fertilizers
N
P
K
NPK(IFFCO)
10
26
26
(MFL)
17
17
17
(RCF)
15
15
15
(ZACL)
19
19
19
(CFL)
14
35
14

Use of rice straw as a source of K for wetland transplanted rice

The fertilizer K could effectively substituted by the kuruvai rice straw incorporation for thaladi rice.

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Biofertilizers for Rice

  • Biofertilizers, a term which refers to microorganisms which either fix atmospheric N or enhance the solubility of soil nutrients. It forms an important component of integrated nutrient management (INM).
  • Nitrogen fixing microorganisms convert about 139-170 million tonnes of nitrogen every year. The total world biological nitrogen fixation is three times that of industrially produced nitrogen.
  • Symbiotic systems such as that of Azolla and Anabaena complex and that of leguminous green manures with Rhizobium and Azorhizobium association can be of particular value to wet land rice crop and renewable biological source supplementing inorganic N for cereals.
  • In wetland rice soil ecosystem, the nitrogen fixation by free-living blue green algae or cyanobacteria also contribute significantly to the replenishment of soil N.

Azolla

  • Azolla is a fresh water fern.
  • It could be used for rice in two ways either as green manure (6 t/ha) before transplanting, or as dual crop (0.5 t/ha) in 7 DAT.
  • It releases the nitrogen to the rice crop only after complete decomposition (8-10 days).
  • Azolla when it is grown as green manure, decomposes readily and releases nitrogen to rice crop.
  • It also enhances the availability of phosphorus than chemical fertilizer on 40th day besides improving the C:N ratio of soils.

Blue green algae

  • These are photosynthetic prokaryotic microorganisms capable of fixing atmospheric nitrogen.
  • It can be applied to rice crop at 10 kg/ha on 10 DAT. ‘Algalisation’ increases the nitrogen content of both grain and straw besides increasing soil fertility.
  • It can fix 20-30 kg N/ha.

Azotobacter

Azotobacter is a free living nitrogen fixing bacteria. It can be applied to rice through seed or seedling or soil.

Azospirillium

Inoculation with Azospirillum promotes early tillering and also the growth of rice and significantly increases filling rate of grain and the grain weight per plant at harvest.

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Method Of Application Of Biofertilizers

  • Bacterial biofertilizers are supplied as carrier based inoculants.
  • Peat or lignite is used as carrier material.
  • Carrier based bacterial inoculants are applied by the following methods:
    • Seed treatment
    • Seedling root dip and
    • Main field application

Seed treatment

  • One package of the inoculant is mixed with 200ml of rice kanji to make slurry.
  • The seeds required for an acre are mixed in the slurry so as to have a uniform coating of the inoculant over the seeds and then shade dried for 30 minutes.
  • The shade dried seeds should be sown within 24 hours.
  • One packet of the inoculant (200g) is sufficient to treat 10 kg of seeds.

Seedling root dip

  • This method is used for transplanted crops.
  • Two packets of the inoculant is mixed in 40 litres of water.
  • The root portion of the seedlings required for an acre is dipped in the mixture for 5 to 10 minutes and then transplanted.

Main field application

Four packets of the inoculant is mixed with 20 kgs of dried powdered farm yard manure and broadcast in one acre of main field just before transplanting.

Azospirillum / Azotobacter

In the transplanted crops, Azospirillum is inoculated through seeds, seedling root dip and soil application methods. For direct sown crops, Azosprillum is applied through seed treatment and soil application.

Azospirillum Number of packets/hectare is

Seed-5 Nursery-10 Seedling dip-5 Main field-10 Total requirement is 30 packets/ha.

Phosphobacteria

Inoculated through seeds, seedling dip and soil application methods as in the case of Azospirillum.

Combined application of bacterial biofertilizers

Phosphobacteria can be mixed with Azospirillum. The inoculants should be mixed in equal quantities and applied as mentioned above.

Points to remember

  • Bacterial inoculants should not be mixed with insecticide, fungicide herbicide and fertilizers.
  • Seed treatment with bacterial inoculant is to be done last when seeds are treated with fungicides.

Storage of packets

  • The inoculant packets should be stored in a cool place
  • The packets may be stored at room temperature
  • The shelf life of the organism under normal condition (Room temperature) is 3 months.

Blue Green Algae

Ten kg. Of composite cutlure of BGA can be applied (by mixing the powdered inoculum with 50 kg of FYM or sand and broacaster) to rice crop on 7-10 days after transplanting.

Azolla

  • Azolla is inoculated on 7th day after transplanting at 500 kg/ha and grown as dual culture.
  • The inoculated Azolla multiply and cover the entire field in 20-25 days after inoculation.

Total estimated demand of biofertilizers for different crops in India

Biofertilizers
Thousand tonnes
Azospirillum
482
Azolla
20
Azotobacter
163
Blue green algae
268
Phosphate solubilizers
276

Estimated demand for various biofertilizers for rice in Tamilnadu

Biofertilizers Area (‘000 ha) Quantity (‘000 tonnes)
Rice
2261
 
Azolla  
20,000
Azospirillum  
7913
BGA  
268
Phosphobacteria  
7914

Growth regulators for getting Better yield

  • Foliar Spray of Brasinosteriods 0.3ppm at PI and flowering increases the grain yield.
  • For increasing the rooting under broadcast method of planting, soaking roots in 25 ppm IBA gives best results.
  • Induction of better rooting for early establishment in rice, root dipping for 16 hours in thiamin solution.

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SSNM for Irrigated Rice

N management

Adopt Real Time N Management by the use of LEAF COLOUR CHART (LCC)

Principle

  • Leaf colour intensity is directly related to leaf chlorophyll content and leaf N status
  • LCC can be used to monitor plant N status in situ in the field and to determine the right time of N top dressing to rice
  • LCC consists of six shades – light yellowish green (No.1) to dark green (No.6)

How to use LCC?

  • Measure the colour of the top most fully expanded and healthy leaf from 10 randomly selected plants
    • Place leaf on top of the LCC. Do not detach the leaf.
    • Take LCC readings every 7 days, starting from 14 days after transplanting (DAT) for transplanted rice and 21 days after seeding (DAS) for direct wet-seeded rice
    • Measure the leaf colour under the shade of your body, because direct sunlight affects leaf colour readings.
    • If possible, the same person should take LCC readings every time.
  • Apply the N fertilizer when leaf colour is below the critical value
    • Use critical value 4 for transplanted rice. If the value < 4, apply N each time @ 35 kg/ha for Kuruvai and @ 30 kg/ha for Thaladi / Samba
    • Use critical value 3 for direct wet - seeded rice. If the value < 3, apply N each time @ 35 kg/ha for Kuruvai and @ 30 kg/ha for Samba

P and K management

  • Determine Indigenous Nutrient supply by Nutrient Omission plot technique
  • Grain yield in omission plot correlates well with the indigenous nutrient supply and so the omission plot yield is taken in the fertilizer calculation for computing indigenous nutrient supply.
  • To produce one ton of rice grains per hectare 2.6 kg P and 15 kg K are needed by the crop

How to establish omission plot?

Establish P (+ NK) and K (+NP) omission plots as duplicate sets in each field and separated from the surrounding field by bunds

  • IPS = P uptake in + NK plot
  • IKS = K uptake in + NP plot

Indigenous nutrient supply includes nutrient contribution from

  • Soil, Irrigation water and Crop residues

Model Fertilizer Calculation

Phosphorus

SSNM approach

[Yield goal: Yield achievable with best management practices under no water limitations

(or)

70-80% of climatic and genetic yield potential

(or)

Approximate recent average yield with good management]

  • Select a yield goal: 8.0 t / ha
  • Use the computed value of P requirement for 1 t / ha rice yield viz., 2.6 kg P/ha for calculation
  • Estimate the plant P requirement: 8 x 2.6 kg P / ha = 20.8 kg P / ha
  • Determine indigenous P supply from P omission plot (+ NK plot) yield: 6 t/ha; 6 x 2.6 kg P / ha = 5.6 kg P / ha from field .
  • Calculate P fertilizer rate: 5.2 (20.8-15.6) x 100/25* = 20.8 kg P/ha (as P 2 O 5 20.8 x 2.29 = 47.6 kg P2O5 / ha) (*Recovery efficiency = 25%)

Potassium

SSNM approach

  • Select a yield goal: 8.0 t/ha
  • Use the computed value of K requirement for 1 t / ha rice yield viz., 15 kg K/ha for calculation
  • Estimate the plant K requirement: 8 x 15 kg K / ha = 120 kg K / ha
  • Determine indigenous K supply from K omission plot (+ NP plot) yield: 6.5 t / ha
  • 6.5 x 15 kg K/ha = 97.5 kg K / ha
  • Calculate K fertilizer rate : 22.5 (120-97.5) x 100/50* = 45 kg K / ha (as K 2 O 45 x 1.2 = 54 kg K2 O / ha)

(*Recovery efficiency = 50%)

Incase if the adoption of P and K omission plot technique is not possible, follow the STCR approach for calculating P and K fertilizer recommendation.

Benefits

The SSNM strategy aims to achieve sustainable, large and economic yields through proper nutrient and crop management by;

  • Following plant need-based N management strategies using the Leaf Colour Chart (LCC) and avoiding N over dose coupled with pest and disease incidence.
  • Using nutrient omission plots to determine the soil indigenous nutrient supply (particularly for P and K)
  • Providing the crop with a balanced supply of nutrients (N,P,K)
  • Replacing nutrients (Particularly P and K) removed with grain and straw to avoid depleting soil nutrient reserves

Economics

The adoption of Site Specific Nutrient Management (SSNM) always recorded higher grain yield viz., averaging 500 to 650 kg / ha in Cauvery Delta than in Farmers Fertilizer Practice (FFP). Therefore, the farmers can get Rs. 2250 to 3000/- per hectare as profit, besides a reduction in N fertilizer dose and reduction in expenditure towards plant protection.

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Green Manures

  • Green manuring is an ancient practice. But due to bulkiness of the green manure, green manuring is not practiced by many of the farmers. Further in rice, besides the absence of green manuring, the profit is less. Considering all these aspects, a rice cum green manure seeder was developed by TNAU.
  • The seeder sows wet seeded rice and the green manure seed (Dhaincha) in alternate rows. Rice to rice distance is 25 cm with green manure row in between. At 40 cm height, the green manure and the weeds are all buried using Cono weeder. A minimum of seven tones of green manure / ha at 40 cm height can be produced and incorporated in situ.
  • In the absence of soil testing, the recommended dose of N is applied in four splits viz., 20DAS, at the time of green manure incorporation, 50 DAS and 70 DAS. The recommended potash in three equal splits is applied along with N during the first three times viz., 20DAS, at the time of green manure incorporation and 50 DAS. Phosphorous is applied basally.
  • Since the seed rate of rice (90 kg / ha) and dhaincha (45 kg/ ha) is high, care in leveling is required. This practice is not advocated during rainy season (Thaladi, late Pisanam) as falling raindrops may disperse the seeds.

Benefits

  • There is no establishment of rice nursery and no transplanting cost
  • Exclusive cultivation of green manure is avoided

Economics

  • Besides green manuring at low cost, due to direct seeding a minimum saving of Rs. 3000 /- per ha in rice cultivation can be saved as compared to transplanting.

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