Presentation made at the WCCA 2001 event in Brisbane, Australia.

1. Enhancing nitrogen use
efficiency in wheat sown into
rice residue and effect of straw
management on soil health in
rice-wheat system in North West
India
Yadvinder-Singh1 (yadvinder16@rediffmail.com)
Manpreet Singh1, H.S. Sidhu2 and John Blackwell3
1Punjab Agricultural University Ludhiana, India
2 CSISA Hub, PAU, Ludhiana
3Charles Sturt University, Wagga Wagga, Australia

2. Acknowledgements
• My colleagues involved in this study
• ACIAR for providing funds for the
study and PAU for providing facilities.
• ACIAR and Rural Solutions, SA for
funding my visit, and making it
possible to attend this congress and
to meet you all.

3. Rice-wheat system(RWS)
Rice - wheat constitutes the most productive system in
NW India, particularly in Punjab.
Total area under RWS in Punjab is 2.6 mha out of total
10 mha in India.
RWS produces about 12.5 t/ha of grains and 15 t/ha of
residues annually in Punjab.
Soils are generally coarse in texture with low organic
matter levels.
There is increasing scarcity of water and labor. Ground
water tables in many areas with > 10m depth increased
from 3% in 1973 to 90% in 2004.
There is development of hard pan at 15-20 cm depth
due to puddling adversely affecting yield of wheat.
Rice is transplanted during June 10-25 and harvested
during Oct 01-15.
Wheat is planted from November 01-15 and harvested
from April 10-30.

4. RICE STRAW MANAGEMENT
• More than 80% of area under rice and wheat is
harvested using combine.
• After combine-harvesting rice residue remains
scattered in the field and is difficult to collect, which
impedes seedbed preparation.
• While about 80% of wheat straw is collected and fed
to cattle, >80% of rice residue (about 22 mt) is
burned annually between 15 Oct-10 Nov because of
no alternate uses.
• The burning has several environmental, human and
soil health implications.
• Rice growers are seeking alternative disposal options,
such as direct seeding of wheat into rice residues.

5. Rice straw management
• After 8-9 yrs of concentrated efforts, PAU, Ludhiana,
CSU, Wagga Wagga and CSIRO Griffith (with funding
from ACIAR) have recently developed a new machine
called ‘Happy Seeder’ which is capable of direct drilling
wheat into heavy rice residue loads, without burning in a
single operation by managing only that part of residue
which is coming just in front of furrow openers thus
minimizing harmful effects of residue burning on soil
health and environment.
• ZT sowing of wheat is known to improve yields, lower
costs resulting in higher profits, leads to more efficient
use of water and other inputs, help reverse soil and land
degradation (such as decline of SOM, soil structural
breakdown, and soil erosion), and reduces negative
impacts on the environmental quality (Erenstein and
Laxmi 2008).

6. N Management in Rice-wheat system
• It is estimated that 50% of the food consumed
worldwide results directly from the benefits of N.
• Fertilizer N to wheat on fields where rice straw is
either burned or removed is generally applied in two
equal split doses; half at sowing and the remaining
half before 1st irrigation at 25-30 days after sowing.
• About 40% of the N fertilizer applied to irrigated
wheat is utilized by the plants due to inefficiency in
application (wrong method or timing of application)
and/or the inherent properties of current fertilizer
products.
• A portion of the “unused“ fertilizer becomes
environmental pollutants, either in the form of potent
greenhouse gases or pollutes rivers and lakes.

7. FERTILIZER N MANAGEMENT GUIDELINES
FOR ZT WHEAT
• The efficiency and N losses associated with the
application method have a major impact on the
success of nutrients in the NT farming systems.
• When possible, place N below the soil surface
(about 5 cm beside and/or below the seed row)
to minimize immobilization and volatilization.
• Apply urea before irrigation/rain.
• Apply more N the first few years after conversion
to NT due to tie-up and volatilization loss of N ,
especially when surface broadcasting N on fine-
to medium-textured soils.

8. N Management in ZT Wheat
INTRODUCTION
• Rice straw contains on average of 0.55% N and
its recycling can supply 40-45 kg N/ha annually.
• No-till and straw mulch affects soil N dynamics,
potentially altering optimum fertilizer N inputs
compared to conventionally tilled soils.
Determining optimum N fertilization rate and
timing is critical to improve yields and economic
sustainability for no-till RWS in the IGP.
• However, little data are available evaluating N
management strategies, optimum N rate
prediction methods under no-till wheat in soils
and climate similar to the IGP.

9. FERTILIZER MANAGEMENT IN ZT WHEAT
• In the long-term (5 to 12 yrs), less N was needed to
maximize yield in NT systems due to higher amount of
potentially mineralizable N in soil (Lafond et al., 2005).
• In another LT study in Montana, the N rates needed to
optimize spring wheat yields were nearly identical for NT
and CT, suggesting similar rates of N mineralization
between no-till and CT systems. (Chen and Jones, 2006).
• In Alberta, broadcast urea (68 kg N/ha) produced higher
barley yield under CT compared to plots under 1 to 6 yrs
NT; however, when urea was banded, yields were similar
between NT and CT (Malhi & Nyborg, 1992).
• Above and many other studies suggest that N responses
among tillage systems are not always consistent. This is
apparently due to differences in soil texture, climate, time
since conversion from CT, straw load, etc.

10. FERTILIZER MANAGEMENT
RECOMMENDATIONS FOR ZT WHEAT
• Information available in the literature
suggests that seed row N should not
exceed 30-35 kg/ha as urea. High rates of
seed row N not only reduce stand, but
increase the risk of delayed maturity.
• Factors that influence how much fertilizer
can be safely applied with the seed
include: row spacing, width of seed row,
soil texture, moisture, organic matter, soil
variability, fertilizer placement, seed
furrow opener, source, and crop.

11. Experimental details
1. Decomposition and N release from rice
residue during wheat growing season
using nylon bag technique
2. Response of wheat to fertilizer N
application
3. Effect of method and timing of N
application on N use efficiency in wheat
4. Effect of rice straw management on soil
fertility
5. Effect of straw management on soil
strength

12. Field after uniform distribution of rice straw using
SMS on combine harvester

13. Happy Seeder machine sowing
wheat into the rice residue

14. Rice residue decomposition during
wheat season as a function of time as
affected by method of placement
(A). Sandy loam (B). Silt loam
Surface placement Subsurface placement
Surface placement Subsurface placement
120 120
-0.2373x
y = 106.01e-0.0788x y = 135.69e
y = 100.49e-0.0777x y = 123.41e-0.2097x
100 R2 = 0.956 R2 = 0.989 100
R2 = 0.941 R2 = 0.940
% weight remaining
% weight remaining
80 80
60 60
40 40
20 20
0 0
0 20 40 60 80 100 120 140 0 20 40 60 80 100 120 140
Days after placement Days after placement

15. Release of N from rice residue at three
wheat growth stages on sandy loam
(mean for two yrs)-Residue load, 8t/ha
Growth Residue Residue Nitrogen
Stage placement decomposition released
Amount % of Amount % of
(t/ha) initial (kg/ha) initial
Maximum Surface 1.4 17.2 -8 -
tillering Buried 2.7 33.8 6 14.6
Boot stage Surface 2.1 26.5 -8 -
Buried 4.0 49.9 12 29.2
Maturity Surface 4.2 51.7 -7 -
Buried 6.5 81.2 28 64.6

16. 2. Nitrogen Management in HS-sown
wheat
• Response to applied fertilizer N
• Time and method of N application

17. Background
• Rice straw contains 40-45 kg N/ha, which
on decomposition becomes part of soil
organic N.
• In high residues on soil surface, efficient N
fertilizer management is a challenge
because of greater N immobilization, higher
losses of N via ammonia volatilization and
denitrification than when residues are
burned or removed from the field.
• The losses of N may be minimized by either
drilling the fertilizer into the soil and/or by
delaying the application of N fertilizer when
a significant portion of residues have
undergone decomposition.

18. Response of wheat sown into rice
residue (using HS) to fertilizer N in on-
farm trials
N rate 2007-08 2008-09 2009-10
(kg/h (n=15) (n=3) (n=3)
a) Grain yield (t ha-1)
Range Mean Range Mean Range Mean
90 - - - - 3.13- 3.3+
3.54 0.21
120 3.93- 4.34+ 4.15- 4.73+ 3.49- 3.6+
4.88 0.38 5.08 0.50 3.59 0.07
150 4.15- 4.44+ 4.33- 4.90+ 3.58- 3.7+
4.80 0.45 5.32 0.51 3.65 0.07
4.27- 4.48+ 4.51- 4.97+ - -
180 4.68 0.38 5.50 0.55

19. Experiment 3.
To study the effect of straw mulch and
fertilizer N management strategies
on yield and N use efficiency of
wheat

20. Treatments
T1. No-N control
T2. 25 kg N/ha drilled (D)+35 kg N surface broadcast
(B)at sowing + 60 kg N/ha top dressed (TD1)at 1st
irrigation (25-30 days)
T3. 25D+35B -30- 30kg N ha top dressed at 2nd
irrigation (55-60 days) (TD2)
T4. 25D+65B-0– 30 TD2
T5. 25D+95B - 0– 0
T6. 25D – 48 (TD1) – 48 (TD2)
T7. 25D+35kg N/ha applied with pre-sowing
irrigation (PSI)-60(TD1)-0
T8. 25D+35PSI–30 (TD1)-30 (TD2)
T9. 25D+65PSI-0-30 (TD2)
T10. 25D+95PSI-0-0

21. Effect of method & time of N application on
yield & NUE of wheat under straw mulch
Treatment Grain yield (t ha-1) RE of N (%)
07/08 08/09 09/10 07/08 08/09 09/10
No N control 2.03 2.38 3.06 - - -
25D+35B–60–0 3.96 4.37 4.92 58.3 35.5 41.3
25D+35B -30- 30 3.82 4.24 4.82 54.2 36.4 41.7
25D+65B-0– 30 4.10 3.82 4.60 59.2 29.2 37.3
25D+95B - 0– 0 4.07 3.48 4.50 60.0 22.6 34.6
25D - 48 – 48 4.76 4.75 4.87 78.3 48.3 43.4
25D+35PSI-60-0 4.17 4.07 4.87 62.5 41.2 39.8
25D+35PSI–30-30 4.26 4.23 4.59 67.5 41.8 38.8
25D+65PSI-0-30 3.97 4.39 4.66 59.2 40.8 36.0
25D+95PSI-0-0 3.77 4.61 4.81 50.0 47.5 38.7
LSD (0.05) 0.38 0.56 0.60 6.10 3.9 4.3.

22. Other observations
• Ammonia volatilization losses:
Total N losses through ammonia
volatilization were small (<2kg/ha)
• Chlorophyll meter readings recorded at
90 days after seeding were related to
grain yield of wheat
• The yield increase was mainly due to
increase in tiller density and spike
length

23. 4. Fertilizer N management in wheat
sown into rice residue using HS
• Under mulch, 2nd irrigation to wheat is
sometimes delayed due to lower evaporation
losses, particularly on fine-textured soils and/or
when rain is received during the early crop
season.
• Under such conditions delayed application of
fertilizer N leads to poor crop growth and low N
use efficiency.
• Field study was conducted during 2010/11 to
study the effect of drilling different amounts of
urea after modifying furrow openers of HS on
wheat yield

24. Effect of high doses of fertilizer N
applied at sowing using modified furrow
openers on wheat yield
Treatment Furrow opener Grain yield
(% of 120 kg (t/ha)
N/ha as urea)
50% unmodified 4.79a 0.26
modified 4.80a 0.18
80% unmodified 3.76b 0.19
modified 4.92a 0.18
20% unmodified 5.10a 0.24
Unmodified- seed and fertilizer in the same row;
Modified- fertilizer side placed

25. 5. Residual effect of straw mulch
applied to wheat on the grain yield
of following rice
• Residual effect of straw much on
grain yield of rice and soil fertility
was studied on fields where
previous crop of wheat was sown
using HS

26. Effect of straw management in wheat on
the grain yield (t ha-1) of following rice
Treatment 2008 2009
(After one (After two
year) years)
Experiment 1 (Sandy loam)
No Mulch 7.10 6.51
With mulch 7.37 (3.8%) 7.27* (11.7%)
Experiment 2 (Silt loam)
No Mulch 7.65 7.40
With mulch 7.92 (3.5% ) 8.01* (8.2%)

27. Effect of rice straw management in
wheat for 3 yrs on grain yield of
following rice at different N levels
N rate (kg/ha) Rice straw Rice straw
removed retained
0 4.37 4.77
60 5.86 6.40
90 6.33 6.74
120 7.13 7.32
150 6.94 7.12
Mean 6.13 6.47
LSD (0.05) Straw: 0.16, N=0.33, Straw x N= ns

28. Effect of recycling of rice straw on grain
yields of rice and wheat after 3 years
Treatment Wheat Rice yield
Wheat Rice yield (t/ha) (t/ha)
No straw 120 kg 4.6a 6.1a
+ 120 kg N/ha
N/ha
+straw 90 kg 4.6a 6.5a
+120 kg N/ha
N/ha

29. Effect of rice residue recycling in wheat
on soil fertility after two yrs ( 2008-09)
Soil Silt loam Sandy loam
property
- straw +straw - straw +straw
Organic 5.3 5.8* 3.9 4.5*
carbon
(g/kg)
Olsen-P 5.3 6.8* 17.1 18.6
(kg/ha)
NH4OAc-K 159 173* 95 105*
(kg/ha)

30. 6. Effect of tillage and straw
mulch on soil strength
• Methodology
• Effect of different tillage systems on soil
strength was studied on 51 fields with
different tillage history using automatic
recording cone penetrometer.
• Five readings were taken from every one
acre field after first irrigation
• Highest penetrometer value was recorded in
the upper 30-cm soil layer.
• The highest value was observed at a depth
of 20-25 cm

31. Sub soil strength (kPa) under
different tillage options
Location Time (yrs) of Roto CT HS N Total
Seeder in use no. of
3 2 1 fields
Gurusar 3220 2887 - 2241 1522 120 24
Kaunke
Sangrur 3579 3160 2548 2274 2090 135 27
Mean 3400 3024 2548 2258 1806 255 51
Roto-seeder is a rotavator with attachment of seed-cum
fertilizer box on the top.

32. Summary
• Rice straw decomposition is about 50% and N
released during wheat growing season is nil
compared with 80% and 70% for incorporated
residue, respectively.
• Response to N application in wheat sown with Happy
Seeder is up to 120 kg N/ha, similar to that for wheat
sown after straw burning/removal.
• Best fertilizer N management practice for wheat sown
into rice residues is to drill DAP at sowing and 48 kg
N/ha each before first and second irrigation.
• Rice straw retention improved soil health and
increased grain yield of following rice in RWS.

33. Summary
• High amounts of fertilizer N can be drilled in wheat
after making suitable modifications in the furrow
design.
• Straw mulching in wheat improved yields of following
rice and likely lead to a saving of fertilizer N (about
30 kg N/ha) in the following rice after 3-4 years.
• Straw mulch improved soil OM, availability of plant
nutrients, and soil physical properties.
• Long-term studies are needed to determine the effect
of tillage and straw mulch on nutrient availability and
soil health.