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, India2 CSISA Hub, PAU, Ludhiana3Charles Sturt University, Wagga Wagga, Australia

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.

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.

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.

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).

• 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.

N Management in Rice-wheat system

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.

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.

N 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.

FERTILIZER MANAGEMENT IN 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.

FERTILIZER MANAGEMENT RECOMMENDATIONS FOR ZT WHEAT

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

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

Happy Seeder machine sowing wheat into the rice

residue

Rice residue decomposition during wheat season as a function of time as affected by method of placement

(A). Sandy loam

y = 106.01e-0.0788x

R2 = 0.956

y = 135.69e-0.2373x

R2 = 0.989

0

20

40

60

80

100

120

0 20 40 60 80 100 120 140

Days after placement

% w

eight

rema

ining

Surface placement Subsurface placement

(B). Silt loam

y = 100.49e-0.0777x

R2 = 0.941y = 123.41e-0.2097x

R2 = 0.940

0

20

40

60

80

100

120

0 20 40 60 80 100 120 140

Days after placement

% w

eight

rem

ainin

g

Surface placement Subsurface placement

Release of N from rice residue at three wheat growth stages on sandy

loam (mean for two yrs)-Residue load, 8t/ha

Growth

Stage

Residue placement

Residue decomposition

Nitrogen released

Amount (t/ha)

% of initial

Amount (kg/ha)

% of initial

Maximum tillering

Surface 1.4 17.2 -8 -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

2. Nitrogen Management in HS-sown wheat

• Response to applied fertilizer N• Time and method of N

application

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.

Response of wheat sown into rice residue (using HS) to fertilizer N in

on-farm trials N rate (kg/ha)

2007-08 (n=15)

2008-09 (n=3)

2009-10 (n=3)

Grain yield (t ha-1)

Range

Mean Range

Mean Range

Mean

90 - - - - 3.13-3.54

3.3+0.21

120 3.93-4.88

4.34+0.38

4.15-5.08

4.73+0.50

3.49-3.59

3.6+0.07

150 4.15-4.80

4.44+0.45

4.33-5.32

4.90+0.51

3.58-3.65

3.7+0.07

1804.27-4.68

4.48+0.38

4.51-5.50

4.97+0.55

- -

Experiment 3.To study the effect of straw mulch

and fertilizer N management strategies on yield and N use efficiency of wheat

TreatmentsT1. No-N controlT2. 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 TD2T5. 25D+95B - 0– 0T6. 25D – 48 (TD1) – 48 (TD2)T7. 25D+35kg N/ha applied with pre-sowing

irrigation (PSI)-60(TD1)-0T8. 25D+35PSI–30 (TD1)-30 (TD2)T9. 25D+65PSI-0-30 (TD2)T10. 25D+95PSI-0-0

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 41.325D+35B -30- 30 3.82 4.24 4.82 54.2 36.4 41.725D+65B-0– 30 4.10 3.82 4.60 59.2 29.2 37.325D+95B - 0– 0 4.07 3.48 4.50 60.0 22.6 34.625D - 48 – 48 4.76 4.75 4.87 78.3 48.3 43.425D+35PSI-60-0 4.17 4.07 4.87 62.5 41.2 39.825D+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 36.025D+95PSI-0-0 3.77 4.61 4.81 50.0 47.5 38.7LSD (0.05) 0.38 0.56 0.60 6.10 3.9 4.3.

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

• 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

4. Fertilizer N management in wheat sown into rice residue using HS

 

Effect of high doses of fertilizer N applied at sowing using modified

furrow openers on wheat yield

 Treatment

(% of 120 kg N/ha as urea)

Furrow opener Grain yield (t/ha)

50% unmodified 4.79a ± 0.26

modified 4.80a ± 0.18

80% unmodified 3.76b ± 0.19modified 4.92a ± 0.18

20% unmodified 5.10a ± 0.24

Unmodified- seed and fertilizer in the same row; Modified- fertilizer side placed

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

Effect of straw management in wheat on the grain yield (t ha-1) of following rice

Treatment 2008 (After one year)

2009 (After two 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%)

Effect of rice straw management in wheat for 3 yrs on grain yield of following rice

at different N levelsN rate (kg/ha)

Rice straw removed

Rice straw retained

0 4.37 4.7760 5.86 6.4090 6.33 6.74120 7.13 7.32150 6.94 7.12Mean 6.13 6.47LSD (0.05) Straw: 0.16, N=0.33, Straw x

N= ns

Effect of recycling of rice straw on grain yields of rice and wheat after

3 years

Treatment Wheat yield (t/ha)

Rice yield (t/ha)Wheat Rice

No straw + 120 kg N/ha

120 kg N/ha

4.6a 6.1a

+straw +120 kg N/ha

90 kg N/ha

4.6a 6.5a

Effect of rice residue recycling in wheat on soil fertility after two yrs

( 2008-09)Soil property

Silt loam Sandy loam

- straw +straw - straw +straw

Organic carbon (g/kg)

5.3 5.8* 3.9 4.5*

Olsen-P (kg/ha)

5.3 6.8* 17.1 18.6

NH4OAc-K (kg/ha)

159 173* 95 105*

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

Sub soil strength (kPa) under different tillage options

Location

Time (yrs) of Roto

Seeder in use

CT HS N Totalno.

offields3 2 1

Gurusar

Kaunke

3220

2887 - 2241 1522

120 24

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.

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.

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.