Strategies to enhance nitrogen use efficiency of low land rice cultivation. Also discussed various loss mechanism.

1. ASSESSMENT OF DIFFERENT N MANAGEMENT
STRATEGIES IN LOWLAND RICE CULTIVATION
CHOWDHURY MONIRUL HAQUE
(neyonchowdhury16@gmail.com)
and
Prof. Pabitra Kumar Mani
(pabitramani@gmail.com)
Department of Agricultural Chemistry and Soil Science
Faculty of Agriculture
Bidhan Chandra Krishi Viswavidyalaya
Mohanpur, Nadia,741252,West Bengal, India

2. GLOBAL SCENARIO OF N CONSUMPTION
Figure 1: Regional and sub-regional share of world increase/decrease in
nitrogen fertilizer consumption, 2014-2018 (FAO, 2015)

3. INDIAN SCENARIO OF N Fertilizer CONSUMPTION
Fig. 2a: Percent share of
India in world fertilizer
consumption over time.
(Bijay-Singh, 2016)
Fig. 2b:Comparision of N,P
& K consumption in India
(FAI,2012)
Fig. 2c:Consumption
of N fertilizer by
different crops.
(FAI, 2012)

4. Nitrogen in Soil-Plant-Atmosphere Systems
NH4 NO3
Nitrification
N Inputs:
Fertilizer
Manure
Residue
Irrigation
Rainfall
Biol. Fix.
Plant
Leaching
DenitrificationVolatilization
NH3 N2O N2, N2O

5. MECHANISM FACTORS
DENITRIFICATION
TEMPERATURE,
SOIL pH,
SUBMERGENCE PERIOD,
NITRATE -N CONTENT,
NITRIFICATION RATE
VOLATILIZATION
SOIL pH,
DEPTH OF WATER,
MICROBIAL ACTIVITY
LEACHING
SOIL TEXTURE,
CEC
TABLE 1: MECHANISM OF N LOSS

6. Fig. 3: Schematic diagram of various pathways of N loss in low land rice
(Source: Bijay-Singh, 2017)

7. Factors Denitrification Volatilization Leaching
SOIL
pH LOW HIGH ---
Salinity --- HIGH ---
Texture HIGH MEDIUM HIGH
Temperature MEDIUM HIGH LOW
Organic C HIGH --- LOW
Topography --- --- ---
WEATHER
Temperature MEDIUM HIGH LOW
Wind Speed --- HIGH ---
Table 2: Factors with their degree of influence on different loss mechanism of Nitrogen

8. FERTILIZER Denitrification Volatilization Leaching
Type MEDIUM HIGH HIGH
Amount HIGH HIGH HIGH
Placement MEDIUM HIGH LOW
Timing MEDIUM MEDIUM MEDIUM
Manure HIGH LOW MEDIUM
CROP MANAGEMENT
Tillage MEDIUM LOW MEDIUM
Cultivar LOW MEDIUM HIGH
Irrigation HIGH MEDIUM HIGH
HIGH LOW HIGH

9. Table 3: Environmental problems associated with fertilizer use.
( Pathak et al., 2016).

10. VARIOUS NITROGEN USE EFFICIENCY PARAMETERS
Partial factor Productivity or PFPN (kg grain yield per kg N applied)
Recovery Efficiency or REN (kg N taken up per kg N applied)
Internal efficiency or IEN (kg grain per kg N taken up)
Agronomic Efficiency or AEN

11. Common NUE values for N for maize, wheat, and rice and for various world regions
(Ladha et al. 2005).

12. Why we are concerned about Use Efficiency of Nitrogen in cereals
Variability of N fertilizer recovery efficiency based on
grain N (RENG) among 452 data points of maize, rice,
and wheat collected from studies across the regions.
Variability of agronomic N use efficiency (AEN)
among 411 data points of maize, rice, and wheat
collected from studies across the regions
Box plot analysis of data reveals very poor use efficiency parameter, Ladha, 2005

13. • Right method of Nitrogen application:
a. Deep placement of Urea Super Granules.
b. Foliar application of Nitrogenous fertilizers.
• Balanced application of fertilizers
• Site Specific Nutrient Management (SSNM):
a. Leaf Colour Chart (LCC)
b. Chlorophyll Meter (SPAD)
Strategies to enhance Nitrogen use efficiency
Contd.

14. • Slow and Controlled Release Fertilizers
a. Nitrification Inhibitors
b. Coated Fertilizers:-
1. Neem Coated Urea (NCU)
2. Sulphur Coated Urea (SCU)
3. Polymer Coated Urea (PCU)
• Resource conservation Technology
• Integrated Nutrient Management
STRATEGIES TO ENHANCE N‐USE EFFICIENCY

15. DEEP PLACEMENT OF UREA SUPER GRANULES:
• Deep point placement of USG (1-2 g) at 5-10 cm depth (reduced zone of lowland paddy).
• Putting urea in mud balls (1:6 v/v) for 1 to 2 d before its application in the field
facilitates the absorption of ammonia in soil colloids, thus reducing leaching losses.
(De Datta,1981)
ADVANTAGES:
I. Limits the conc. of N in flood water and in the surface oxidized layer.
II. Decreases N losses through runoff, ammonia volatilization and denitrification.
DISADVANTAGES:
I. Labour intensive( require skillful labour to place the USG in right place)
II. Lack of suitable applicators.
III. Lack of availability.
RIGHT METHOD OF NITROGEN APPLICATION

16. Table 4 : Productivity of rice (kg ha-1) with surface application and deep placement of N-
fertilizers in different ecosystems of rainfed lowland in India.
(Source: Pande and Mohanty, 1986)
CASE STUDY

17. CASE STUDY
Fig 4: N concentration in floodwater
with different methods of N fertilizer
application
(Source: Pat
Potential for NH3 volatilization loss:
Prilled urea>Neem coated urea>USG
Fig 4(a): Changes in NH4
+-N in soil
(0–15 cm layer) with different
methods of N fertilizer application

18. ADVANTAGES:
I. Less subjected to surface runoff, microbial immobilization, volatilization and
denitrification.(Balasubhramanium et al,2004)
II. Quick recovery from N deficiency in dry farming areas where soil
moisture is a constraint
DISADVANTAGES:
I. Washing out of applied fertilizer after heavy rainfall.
II. Need frequent application which is labour intensive and cost ineffective.(Novoa
and Loomis,1981)
FOLIAR APPLICATION

19. SSNM can be : (1) Prescriptive and (2) Corrective (Ladha,2005)
I. Prescriptive N management relies on information generated before the
planting of a crop.
II. Corrective N management method employ diagnostic tools to assess
crop N status during the growth of the crop which are used as the basis
for decision about further N application- Leaf Colour Chart (LCC) and
Chlorophyll Meter (SPAD).
SITE SPECIFIC NUTRIENT MANAGEMENT (SSNM)
SSNM has been proposed as an approach to tailor fertilizer application to match field-specific
needs of crops to improve productivity and profitability.(Buresh, 2010)

20. Feed the plant need!
Inorganic
fertilizer
N-P-K
Climate
Crop need for
nutrients
Manure
Indigenous nutrient
supply
Irrigation water Crop residues
Soil
How do I decide about fertilizer
Conceptual framework of SSNM

21. • It depicts gradients of green hues based on wavelength characteristics
of rice leaves from yellowish green to dark green.
• LCC Score ≤ 4 is used extensively in India for further application of N in
lowland rice.
ADVANTAGES:
I. Easy to handle
II. Less expensive
III. An accurate tool for determining N status in Rice fields.
LEAF COLOUR CHART (LCC)

22. CASE STUDY
Table 5: Effect of fertilizer N rate and use of leaf colour chart on nitrogen use efficiency
of hybrid rice cultivar PHB 71 during 2006–08
(Source: Gupta et al., 2011).

23. Table 6: Evaluation of leaf colour chart (LCC) based real-time N management in rice vis-a`-vis
fixed time blanket N recommendations/farmers’ practice in different Indian states in
the Indo-Gangetic plain.
(Source: Bijay Singh,2010)
a Standard deviation of mean ; b Range of total N applied; c Includes a basal application of 20 or 30 kg N ha-1
along with LCC based N applications; d Farmer’s practice

24. • It offers relative measurements of leaf chlorophyll content.
• SPAD value ≤ 35 or 37 is used as critical value for further topdressing of N in lowland rice
fields.(Bijay-Singh,2017)
• Or sufficiency index approach may be adapted.
ADVANTAGES:
I. Highly sophisticated and sensitive tool to measure in situ N status in the crop.
DISADVANTAGES:
I. High cost
II. Linear relationship of SPAD value and N Status varies with groth stages and cultivars.
III. Environmental and other stress factors (pest, disease etc.) confound the SPAD reading
( Ladha et al,2005)
IV. It has no use until the leaves are fully expanded.
CHLOROPHYLL METER (SPAD)

25. Table 7: Effect of SPAD meter based fertiliser N management on fertiliser N use efficiency in
rice in India.
(Source: Bijay Singh, 2016a)
AEN†, agronomic efficiency of applied N; REN, apparent recovery efficiency of applied N; PFPN, partial factor productivity of applied N.

26. Slow and controlled release fertilizers
Slow and Delayed N release pattern commensurate N requirement with the crop demand.
Table 8:Various Slow- and controlled release fertilizers.
(Pathak et al., 1998)

27. • Slow conversion of NH4
+ to NO3
- due to nitrification inhibition
ADVANTAGES:
I. Higher availability of ammonium ion conc. in soil which is less
subjected to leaching and denitrification losses
II. Inhibitory effect on CH4 oxidation and N2O emission.
DISADVANTAGES:
I. High cost.
II. Lack of availability in Indian market.
NITRIFICATION INHIBITOR

28. CASE STUDY
Fig. 7: Soil NO3− content in a rice field with and without fertilizer nitrogen and different
nitrification inhibitors NCU, NU, UD over 70 DAT (bars indicate mean N2O–N flux ±S.D. for
five treatments on each DAT)
( Majumdar et al., 2000)

29. NEEM COATED UREA (NCU)
• Oil derived from seeds of neem contains melicians of which
Epinimbin, Deacetyl, Salanin and Azadirachtin are the active
fractions which have dose dependent nitrification inhibition
action.(Mohapatra et al.,2015)
• Prilled urea are uniformly coated with Neem oil, Nimin (Neem Seed
Kernel Extract), Neem Cake etc.

30. NCU
product
Coating
thickness
Location % increase in
grain yield in NCU
over uncoated
% increase in
REN in NCU
over uncoated
References
NCU 20% neem cake Haryana 1.7 -
Nehra and Dhindwal
(2010)
NOCU 0.5 kg neem oil t-1
New Delhi No increase -
Kumar et al. (2010)
NOCU 1.0 kg neem oil t-1
New Delhi 29.0 -
Kumar et al. (2010)
NOCU 0.5 kg neem oil t-1
New Delhi 12.6 11.9
Kumar et al. (2011)
NCU 30 % neem cake Dharwad 9.1 -
Sannagoudra et al.
(2012)
NOCU 500ml q-1
Dharwad No increase -
Sannagoudra et al.
(2012)
NIMIN 1% nimin Kandhamal 6.8 13.9
Mohapatra et al. (2015)
Table 9 : Per cent increase in yield of rice and nitrogen use efficiency by applying different variants
of Neem Coated Urea (NCU) over untreated urea.

31. • Molten elemental Sulphur was sprayed over pre heated urea prills.
• Cracks and pores of the Sulphur coating are Sealed by micro
crystalline wax sealant.(Ahmed et al,2008)
ADVANTAGES:
I. Controlled dissolution rate of fertilizer N which synchronizes with
peak period of N demand of crop.
DISADVANTAGES:
I. SCU is prone to non uniform distribution of damaged and perfectly
coated granules.
II. Unavailable in India.
SULPHUR COATED UREA (SCU)

32. CASE STUDY
Fig 8: Dynamics of NH4
+- N in the floodwater and volatilization loss in alkali soil
following application of urea or slow/controlled release urea sources to rice, wet
season 1985.
(Rao et al., 1987)

33. Table 10: Effect of control release fertilizers on rice cultivation in different soils.
(Source: Khan et al, 2015)

34. • Urea granule is enveloped in a permeable or semipermeable
organopolymer membranes like Thermoplastics, Resins,
Polyolefin etc.
ADVANTAGES:
I. Controlled dissolution rate of fertilizer N which synchronizes with
peak period of N demand of crop.
DISADVANTAGES:
I. Lack of low cost technology to manufacture suitable polymers.
II. Unavailable in India.
POLYMER COATED UREA (PCU)

35. Why controlled release coated urea (CRCU)?
The 2nd and 4th reactions produce required nutrients for plants. Since plants need only a small quantity of
food during early growth, excess nutrients are lost due to leaching.
In the 5th and 6th reactions, the N is lost through hazardous gaseous emissions.
The production of a more suitable CRCU is therefore needed to solve these problems. (Azeem et al., 2014)
When Urea applied to the
soil, urea undergoes a
series of biological,
chemical and physical
transformations to produce
plant available nutrients as
follows. (Trenkel 2010)

36. Diffusion mechanism of controlled
release;
(a) Fertilizer core with polymer coating,
(b) Water penetrates into the coating
and core granule,
(c) Fertilizer dissolution and osmotic
pressure development,
(d) Controlled release of nutrient
through swollen coating membrane.
Probable release mechanism for coated fertilizers called the multi-stage diffusion model
(Shaviv , 2005 )

37. CASE STUDY
FIG 9: Comparison of ammonium N release in PCU over normal Urea in flooded water
in respect of time
-------- 8% PCU
-------- 12% PCU
-------- NORMAL UREA
(Source : Fageria et al,2014)

38. Polymer Sulphur Coated Urea – widely accepted controlled release fertilizer,
South Asia, Europe , USA
The nutrient release pattern should match
exactly the nutrient uptake curve of the crop
The coated fertilizer release mechanism is basically a nutrient transfer from the
fertilizer–polymer interface to the polymer–soil interface, driven by water
Lammel, 2005

39. CASE STUDY
year Treatment Rice
yielda
(kg ha−1)
15N
Recoveryb
(%)
Residual
15Nb
(%)
15N lossb
(%)
Harvest
Index
2008
Urea
7509b 24.5b 22.6a 52.9a 0.49a
A blend of 6 % (w/w)
polymer-coated urea and urea
7483b 27.5b 27.3a 45.2ab 0.50a
6 % polymer-coated urea 7864a 35.4a 28.3a 36.4b 0.50a
2009
Urea 7433b 25.7c 24.3a 50.0a 0.47a
8 % polymer-coated urea 7477b 48.0a 26.7a 25.3b 0.45b
12 % polymer-coated urea 8067a 37.9b 25.2a 36.9b 0.49a
Data are means of triplicates. Lowercase letters indicate significant difference at p<0.05 among treatment
means within a single crop season.( a. Observed from 30-m2 field plots b. Observed from 15 N microplots c.
Observed from 15 N microplots) (Wang et al., 2015)
Table 11: Comparsions of rice grain yield, N recovery, residual N and N loss, harvest index for the
conventional three split urea applications and a single basal application of the polymer-coated urea
fertilizers.

40. • After introduction of combined harvester a large portion of rice straw
remain unutilized which may be a good source of organic N by the
application of this technology. (Singh et al,2005)
ADVANTAGES:
I. Long term application can increase readily mineralized organic-N.
thus can reduce the amount of chemical fertilizer.
DISADVANTAGES:
I. Lack of good incorporator.
II. At initial stage N immobilization > N mineralization
RESOURCE CONSERVATION TECHNOLOGY

41. Resource Conserving Technologies (RCT)
1. No-tillage
2. Laser land leveling
3. Direct seeding of rice
4. Leaf colour chart for N
5. Crop diversification
Conventional RCT

42. CASE STUDY
Table 12: Effect of rice straw management, tillage system and N fertilizer on recovery
efficiency of applied N in rice on two soils.
(Source: Yadvinder Singh et al,2009)

43. • Biological , Chemical, Cultural practices of nutrient management are
integrated.
ADVANTAGES:
I. Mitigate the ill effect of over use of synthetic fertilizers.
II. N loss is minimized and soil health is well maintained.
DISADVANTAGES:
I. Lack of proper knowledge which cause partial or over adaption that
cause negative result.
INTEGRATED NUTRIENT MANAGEMENT (INM)

44. CASE STUDY
Table 13 : Effect of nitrogen, farmyard manure and fertimine application on yield of
rice during two years
(Source: Thind et al,2016)

45. • Being expensive adoption of Chlorophyll Meter (SPAD) is less.
• Lack of equipment and labour restrain the wide adaptability of fertilizer
placement technique as well as foliar application.
• Low profitability and lack of stakeholders hinder the large scale adaption
of nitrification inhibitors and control release fertilizers.
• Technology needs to be evaluated for long term impacts in case of
resource conservation technologies and INM.
• Being least expensive and easy to handle LCC based management is the
best option matching N application with crop demand in real time along
with different neem oil coated urea products.
CONCLUSION

46. THANK YOU