Modified SRI and super-high yield of hybrid rice in Sichuan Basin

Jia-guo Zheng, Xin-lu Jiang, and Zhong-zhi Chi

Sichuan Academy of Agricultural Sciences

Introduction

• To assure food security in the rice-consuming countries of the world in 2030, farmers will have to produce 50% more rice than now with improved quality to meet consumers’ demand.

• The task of making further gains in production is more difficult when rice yields are already at a high level.

• SRI, developed in Madagascar and synthesized in the early 1980s, offers opportunities to researchers and farmers to expand their understanding and accomplishment of the potential yield of rice varieties.

• Why SRI can make advances in the rice yield?

• The methodology makes 3 main changes: – Transplant younger seedlings, preferably 8-15

days old; – Plant the seedlings singly, rather than in clumps

of 3-6 plants, and with wider spacing; and – Keep the paddy soil moist but not continuously

saturated during the plants' vegetative growth phase.

• To achieve super high yield, rice researchers in China began evaluating and introducing SRI from 2000.

SRI is ideas, not a technology ---- Prof. Norman

Materials and methods for evaluation

• Experiment 1: Compared the original SRI methods (15 d seedlings, 40×40cm, single seedlings) with local techniques (CK) (50 d seedlings, 30×15cm, 1 seedling with 6 tillers).

• Experiment 2: Transplant rice seedlings at different densities, i.e., 40×40cm, 40×45cm, 45×45cm, 45×50cm, 50×50cm, and 55×55cm.

• Experiment 3: Transplant with different planting patterns, i.e., – CK = 50 d seedlings, 30×15cm, 1 seedling with 6

tillers – SRI = 15 d seedling, 40×40cm, single seedling – S+3 (square with 3 seedlings) =15 d seedling,

40×40cm, 3 seedlings per hill – S+T (square with triangle) =15 d seedlings, 40×40cm,

transplanting 3 seedlings separated at 7 cm, making a triangle in each hill

– O+T (oblong with triangle) =15 d seedlings, 40×45cm, transplanting 3 seedlings per hill separated by 7 cm each, making a triangle in each hill

• Experiment 4: Evaluate the suitability of different super-hybrid rice varieties for use with SRI or conventional cultivation methods.

• Field demonstrations have been undertaken with modified SRI methods in a large scale at different experiment sites.

• Extension has been guided by the provincial agricultural extension center.

30cm

15cm

Farmer practice

40cm

40cm

Original SRI

40cm

35cm

7cm

Modified SRI: oblong with triangle

Results and discussion

SRI is a promising way to increase rice yield

• The average grain yield in Sichuan Province from hybrid rice with farmers’ practice has resulted in yields of about 8.5 t/ha.

• When SRI methods were first introduced, rice yield was increased by 20%

• Then with modified methods (oblong and triangle), the increase was still higher, at about 55%.

Table 1. Yield response to different planting patterns in rice

Transplanting pattern

Yield(t/ha)

Compared to CK

Increase in t/ha

Increase in %

CK 8.65 -- --

Original SRI 10.42 1.77 20.4

Oblong and triangle SRI

13.39 4.74 54.8

SRI promotes more vigorous growth of the rice plant

• With SRI methods, leaf blades become bigger, especially the functional leaves (Table 2).

• Plant height and culm length become longer. The stem diameter of the 4th internode (from the top) was 0.49 cm for SRI, 12% more than for CK. Hence it was documented that SRI management results in a very strong stem.

• Leaf area index (LAI) was also much higher for SRI methods than CK.

Table 2. Leaf blade size (cm) in response to SRI

Planting pattern

3rd leaf 2nd leaf Flag leaf Average

Length Width Length Width Length Width Length Width

SRI 64.25 1.57 71.32 1.87 57.67 2.17 64.41 1.87

CK 56.07 1.43 62.03 1.57 48.67 2.01 55.56 1.67

Stem Root system

Fig 1 Dynamic change of leaf area index

2

3

4

5

6

7

8

6- J ul 16- J ul 26- J ul 5-Aug 15-Aug 25-Aug

Date

LAI

SRICK

SRI gives high output with fewer inputs, but requires more manual work.

• SRI plants showed fewer insect and disease problems, and seed requirements were reduced by 50-90%. There was saving of water, by as much as 30%, with high WUE .

• However, SRI requires good and careful land leveling to facilitate good water control and minimal applications of water. Also, more time is needed for weed control because flooding is not used to suppress weeds.

Limiting factors for adoption

• When the number of foundation plants is less, this appears not suitable in an ecosystem with the low solar radiation of Sichuan.

• Single plants in a square pattern with wide spacing do not produce sufficient panicles per unit area. Consequently, yield potential is limited. Farmers want to maximize the number of panicles/m2, not panicles/hill.

• The oblong and triangular planting method appeared to be a valuable adaptation of SRI, increasing plant density by 50% while maintaining good exposure of individual plants to the sun and air.

It is hard to transplant young seedlings at 2-leaf age in multiple cropping system.

• Traditionally older-aged seedlings (about 7-leaf) are transplanted into the paddy fields after wheat harvest.

• If very young rice seedlings are used, the sowing date has to be postponed, which leads some unexpected results such as late maturity, less yield, and difficulties in field management.

Organic fertilizers are often in short supply.

• Because of the popularity of reduced or zero-tillage, local livestock populations are now decreasing in the rural areas. Hence, farmers now cannot get enough manure for organic fertilization.

• There is not a tradition of preparing compost from plant vegetative material.

• Management measures such as manual weeding and keeping the soil moist are more complex than present practices, requiring more labor with SRI.

Improved SRI methods in Sichuan

Using tray nursery to raise seedlings

• The seedling nursery is managed under upland conditions, using plastic trays.

• Seedlings are removed carefully from the nursery and are transported to the paddy field, gently transplanted into the field within 15-30 minutes.

• This careful handling avoids having a long recovery time after transplanting, and leaf age can be extended to 3.5-4.5.

• Transplanting density

7

8

9

10

11

12

13

14

Space ( cm)

Yiel

d (t

/ha)

Best trans-planting density is seen to be 40-45 x45-50 cm.

Oblong with triangle transplanting pattern.

7

8

9

10

11

12

13

14

CK SRI S+3 S+T O+T

Yield(T/ha)

Transplanti ng pat tern:S+3= Square wi th 3 seedl ings; S+T=Square wi th

t ri angle;O+T=Oblong wi th t riangl e

Transplanting of 3 separated seedlings per hill in a triangular pattern produces more panicles/m2 and greater panicle size, giving more 'edge effect' throughout the growth period.

752.6 737.2 724.5 696.1

576.5

500

550

600

650

700

750

800

850

公斤

/亩

3叶/5000 4叶/6000 5叶/7000 6叶/8000 7叶/13636

叶龄与密度的组合

移栽叶龄与密度组合的稻谷产量（2005，新都）

Younger seedlings are better

Application of herbicide when needed.

• Because of the wide space between plants and more fertile soil, there are more weeds with SRI than with conventional cultivation, especially in zero-tillage fields.

• But by combining herbicides and mulching measures, weeds can be reduced.

Adding chemical fertilizers to promote plant growth.

• The effect of organic fertilizer is slower than chemical fertilizer. Hence, chemical fertilizer is used to promote tillering and get more panicles during the productive tillering stage.

Inhibiting tillering after productive tillering stage.

• The tillering ability of rice plants is very strong, and the panicle-to-tiller ratio is often less than 50% in SRI.

• Mid-season drainage is thus recommended for SRI fields to inhibit excessive tillering.

Making shallow furrows before transplanting in zero-till fields.

• This is appropriate for the alternate wetting and drying (AWD) method, an effective and easy method for SRI water management.

• Shallow furrows help to implement AWD, maintaining aerated soil surfaces while some water is maintained or alternated in the furrows and moistens the root zone.

Making shallow furrows

Super-hybrid rice and the suitability to different cultivation systems

• Based on the experience with high yield breeding in China and new plant type breeding in IRRI, a research project on breeding of super rice has been established since 1996.

• The project defined ‘super rice’ as a varietal type -- combining the harmonious plant type with heterosis to achieve super high yield, good eating quality, and multiple resistance to diseases and pests.

• Super-rice varieties released in China since 2005 now total 138 varieties.

• 11 super-hybrid rice varieties were collected for use in 2007-2008 trials, using both SRI practice and farmer practice to analyze the suitability of these varieties.

VarietiesSRI Farmer practice

SRI-FP±kg/haYield

(kg/ha)to CK±kg/ha

±%Yield

(kg/ha)to CK±kg/ha

±%

Liangyou-Peijiu

10,701.15

1,948.65 22.26 8,791.65 -95.85 -1.08 1,909.50

II youhang 111,097.9

02,345.40 26.80 9,827.25 939.75 10.57 1,270.65

Nei2you 6 9,095.85 343.35 3.92 9,188.70 301.20 3.39 -92.85

Zhunliangyou 527 8,182.20 -570.30 -6.52 9,383.85 496.35 5.58 -1,201.65

D you 527 9,627.00 874.50 9.99 9,335.70 448.05 5.04 291.30

II you 7 8,527.65 -224.85 -2.57 9,122.55 235.05 2.64 -594.90

II you 602 8,733.15 -19.35 -0.22 9,075.60 187.95 2.12 -342.45

Shanyou 63(CK) 8,752.50 0.00 0.00 8,887.50 0.00 0.00 -135.00

Zhongzheyou 1 9,766.50 1,014.00 11.59 8,620.95 -266.55 -3.00 1,145.55

Chuanxiang9838

11,046.30

2,293.80 26.21 9,073.65 186.15 2.09 1,972.65

B you 827 9,956.10 1,203.60 13.75 9,358.65 471.15 5.30 597.45

II you 084 9,453.75 701.25 8.01 9,417.60 530.10 5.96 36.15

Average 9,653.40 900.91 10.29 9,199.65 312.15 3.51 453.75

11 SHR varieties can be classified• SRI-appropriate types: • 4 varieties (Chuanxiang 9838, Zhongzheyou 1, II youhang 1,

and Liangyou-Peijiu). These are suitably cultivated with young seedling age (less than 4.5 leaf age), wide spacing (7.5 hills/m2 or 22.5 seedlings/ m2), and high fertilizer application. They heave excellent tillering ability, with the last 3 leaves quite erect, and are strongly resistant to lodging.

• Farmer practice-appropriate types: • 4 varieties (Nei 2 you 6, Zhunliangyou 527, II you 7, and II you

602) can be transplanted better at an older seedling age (more than 6-leaf age, 1 seedling with 6 tillers), with high density (30×15cm), and medium fertilizer applications.

• Neutral types: • 3 varieties (D you 527, B you 827, and II you 084). These can

give good yield both with SRI and FP management.

SRI extension in Sichuan

• SRI was become the province’s preferred technique from 2005, and now it is considered as a principle technique for “rice high yield creation” in Sichuan Province. The application area is expanding rapidly, and the provincial yield record for rice production is being broken year after year (Table 4).

• SRI has been applied for 6 years in Guanhan City since 2003. Its rice grain yield reached 12.8 t/ha in 2008, certified by the Provincial Department of Agriculture and national experts. This is a new record of super-high yield in Sichuan ecosystem.

Year 2004 2005 2006 2007 2008

SRI area (ha) 1,120 7,290 57,500 116,667 204,000

SRI yield (t/ha)

9.10 9.44 8.82(drought

year)

8.99 9.41

Conv. yield (t/ha)

NA NA NA 7.5 7.71

SRI increment (t/ha)

NA NA NA 1,489 1,698

SRI % increase in yield

      19.85 22.03

SRI added net income (RMB/ha)

      1,574 1,956

Economic returns to different patterns, 2005

Model

Input Yield Output Benefit Increase

￥ /ha Kg/ha ￥ /ha ￥ /ha ￥ /ha

Super high-yield 7,320 10,500 15,120 7,800 2,229

High yield 6,750 9,750 14,040 7,065 1,494

CK (FP) 6,525 8,400 12,096 5,571 0

Yield components for record harvest in Guanghan city (2008)

Panicles/m2 228 Grains/panicle 191 Seed set rate 85.5% 1000 grain weight 29.5 Certified yield 12.8 t/ha Harvested area 743.4 m2

Conclusions

• SRI is a new technique for rice culture being introduced in many areas across the world, but the techniques used in Madagascar are not all suitable for Sichuan.

• A modified version of SRI suited to the Sichuan agro-ecosystem can increase rice yield significantly in this province and maybe elsewhere. The modifications include: changes in transplanting density, leaf age, planting pattern, and field management.

• SRI is not a fixed technology but rather a set of ideas for creating a more beneficial growing environment for rice plants.

• As such, there should be continuing variations and evaluations by researchers and also by farmers to further modify and improve this system.

THANKS 谢 谢