1185 - Agricultural Water Savings by SRI for Future Water Management
Agricultural Water Savings by SRI for Future Water Management in Sichuan, China ZHENG JIAGUO Sichuan Academy of Agricultural Sciences
1 General information on SRI application in China• Brief review of the spread of SRI• Preliminary evaluations of SRI• Improvements in SRI methods for Sichuan• SRI extension in Sichuan
The spread of SRI in China• SRI was developed in Madagascar, being synthesized in the 1980s.• Prof. Yuan Long-ping validated SRI methods with his super-hybrid varieties in 2001, and hosted an international SRI conference in Sanya, China in 2002.• The most active institutions for SRI research have been the China National Rice Research Institute (CNRRI) and Sichuan Academy of Agricultural Sciences (SAAS).• SRI has spread throughout China, with some tech- niques different among provinces and some partial use.• The concepts and methods of SRI can be used with hybrid rice, Japonica rice, and even with other crops
SRI is a promising methodology toincrease rice yield and water productivity• The average yield from hybrid rice in Sichuan is 8.5 t/ha. • When SRI methods were first introduced, they could increase rice yield by 20%, • With modification in the method of transplanting (oblong and triangle method), the increase achieved was still higher, almost 55% (Table 1).• The spacings used in ‘modified SRI’ are considerably greater than in the original SRI.
Table 1. Yield response to different planting patterns in rice Compared to CK Yield Transplanting pattern (t/ha) + t/ha +% CK 8.65 -- -- SRI – standard spacing 10.42 1.77 20.4 Triangle version of SRI 13.39 4.74 54.8Table 2. Leaf blade size (cm) in response to applicationof SRI methods 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
SRI promotes more vigorous growth• With SRI methods, rice plant phenotypes from any given genotype are improved• Leaf blades become bigger, especially the functional leaves (Table 2)• Plant height and culm length become longer• Leaf area index (LAI) is also much higher compared to CK.
Comparison of dry-matter accumulation Rice Green Wither- Pani- Bio-Method Stem Sheath ed leaf stage leaf cle mass Full 6,396 6,555 7,169 316 2,362 24,902 heading SRI Mature 4,109 3,266 3,390 2,667 13,592 25,407 Full 3,775 5,595 3,881 254 1,205 14,710 heading CK Mature 2,475 3,065 1,661 1,639 7,936 15,833 FullSRI over 69.4 17.12 84.7 24.07 96.0 59.1 heading CK +/-% Mature 66.0 6.6 104.1 62.67 71.3 60.5
Lower inputs, especially water-saving• SRI plants showed fewer insect problems and diseases, and seed requirements were reduced by 50-90%.• During the rice-growing season, irrigation water was reduced by 25.6%.• Both WUE and IWUE were higher, by 54.2% and 90.0%, respectively, thereby significantly reducing water consumption.
Limiting factors for adoption• The number of foundation plants is less with SRI.• It is hard to transplant the young seedling at 2-leaf age in multiple cropping systems.• Organic fertilizer materials are in short supply.• Certain management measures such as timely weeding and keeping the soil moist are considered too complex and laborious.
① Using tray nursery to raise seedlings• The seedling nursery is managed under upland (unflooded) conditions, with plastic trays.• Seedlings are removed carefully from the nursery and are transported quickly and placed gently into paddy field within 15-30 minutes.• This avoids a long recovery time (there is little transplant shock); leaf age can be extended this way to 5.5.
② Modified SRI: oblong with triangle 40cm 7cm 35cm
Transplanting pattern and yield results 14 13 12 Yield(T/ha) 11 10 9 8 7 CK SRI S+3 S+T O+T Tr anspl ant i ng pat t er nS+3 = Square with 3 seedlings; S+T= Square with triangle;O+T = Oblong with triangle
Relation between yield and transplanting density with triangular transplanting configuration 14 13 12 Yield (t/ha) 11 10 9 8 7 40× 40 40× 45 45× 45 45× 50 50× 50 55× 55 Space ( cm)
⑦ Shallow furrows in field for drainage• 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 remains in the furrows and moves laterally to moisten the root zone.
SRI extension in Sichuan• Extension has been guided by the Provincial Agricultural Extension Bureau.• By 2010, the SRI area in Sichuan had reached >300,000 ha, starting from 1,133 ha in 2004.• The average SRI yield has been 9.5 t/ha, representing an average increase of 1.8 t/ha over the province average paddy yield.
Table 4. Extension of SRI in Sichuan province Year 2004 2005 2006** 2007 2008 2009 2010 SRI area (ha) 1,133 7,267 57,400 117,267 204,467 252,467 301,067 SRI yield (kg/ha) 9,105 9,435 8,805 9,075 9,300 9,495 9,555 Conv. yield (kg/ha) 7,740 7,650 7,005 7,395 7,575 7,710 7,740 SRI increment (t/ha)* 1,365 1,785 1,800 1,680 1,725 1,785 1,815 SRI % increase in yield* 17.64 23.33 25.7 22.72 22.77 23.15 23.45 Grain increment (tons) 1,547 12,971 103,320 197,008 352,705 450,653 546,436 Input increment by SRI 834 969 736.5 771 900 1,020 1,200 (RMB/ha) Grain price (RMB/kg) 1.44 1.44 1.44 1.5 1.8 1.84 1.95 Additional net incomeattributable to SRI in Sichuan 1.28 11.64 106.51 205.10 450.85 571.69 704.27 (million RMB )*
2. Water savings for rice• General information about Sichuan province• Water-using characteristics in rice cultivation• Individual research on water-saving for SRI• Impact of water-saving techniques and demonstrations in Sichuan
Sichuan is located in southwest China• The rainfall is 1,000 mm annually.• Water resources are about 3,040 m3 per capita, which is higher than Chinas average.• The hilly regions have the most serious water shortage. The water resources per capita here are 940 m 3, just 30.9% of the province average, and less than 40% of the national average of 2,477 m3.• Agriculture consumes 80% of the total water resources in Sichuan.• Water use efficiency (WUE) of staple crops such as rice, maize, and wheat is about 0.9 kg/m3.
① Irrigation systems well developed on Chengdu Plain• Chengdu Plain covers 10,000 km2.• Dujiangyan irrigation system, built over 2,000 years ago, enables irrigation automatically.• The thermal conditions provide adequate temperature for the rice-wheat cropping system.• But WUE is lower because of flood irrigation or string irrigation.
② Seasonal droughts are the main restricting factor in hilly areas• Seasonal droughts are quite frequent, due to the uneven distribution of rainfall during rice growth.• Drought disasters, such as withered rice seedlings or waiting for rainfall to transplanting, occur every year. Withering Yellow leaf
Drought Spring Summer Hot summerSow Transp. Elongation Heading Mature Nursery Tiller Panicle initiation Filling and ripen Lack of Delay Yellowwhither Low seed set water The influence on rice from seasonal drought in Sichuan hilly region
③ Groundwater resources are seldom used directly• Agriculture relies mostly on surface water.• Rice depends on permanent paddy field water storage in the hilly region, because there are no reservoirs or irrigation projects.
Experiences on rice water-saving Landscape and the experiment plots
① Dry seedbed nursery• The seedbed is established under upland conditions and kept dry during the nursery period.• Because rainfall can be used directly in upland seedbeds, more than 50% of the irrigation water is saved during the nursery stage (about 45d, ≥7 leaf age). Also, seedling quality is much better than with the wet seedbed nursery.
Table 5. Water consumption for rice nursery Rain- Total Comparison to CK fall consumption (±) (m3/ha) (m3/ha) Irrigation water (m3/ha) (m3) (%)DS 315 95.1 410.1 484.1 54.14WS (CK) 315 579.2 894.2 -32.27 -Table 6. Seedling quality differences between nursery methods Dry Recov- Emer- Seed- Dry wt/ No. of Height matter ery gence ling fresh tillers/ (cm) (g/seed- time (%) (%) (%) seedling ling) (days)DS 92.6 89.2 29.98 0.63 24.42 4.36 0.5CK 82.7 79.2 39.49 0.57 17.17 2.94 7.5 DS: Dry seedbed; WS: Wet seedbed
② Mulching in rice cultivation• In seasonally drought-affected regions, can save 30% of water, and increase grain yield by 6%; increase WUE by 0.52 kg/m3; and increase IWUE by 1.24 kg/m3.• Mulching conserves soil moisture and suppresses weeds.• Small farmers have the labor to manage the mulching.• Mulching with plastic film saves more water and reduces losses to drought. But plastic pollution can become a serious problem.
Table 7. Comparison of irrigation water amounts (m3 per ha) in different growth stages during the rice-growing seasonTreatment LP T-SF SF-B B-FH AFH MBR 1,650.0 651.9 603.75 327.6 273.3 CK 1,650.0 844.8 1,085.1 1,629.3 912.6 MBR: mulching of wheat straw into broad rows; CK: farmers’ practice. Effective rainfall was 2,585.1 m3·hm-2. LP: Land preparation; T: transplanting; SF: sun field; B: booting; FH: full heading; AFH: after full heading. The same is as in the following tables.
Table 8. Comparison of water efficiency under different models Irriga- Yield TWC WUE To CK IWUE To CK tion (kg·hm-2) (m3·hm-2) (kg·m-3 ± (kg·m-3) ± (m3·hm-2) (kg·m-3) (kg·m-3)MBR 9,467.10 3,506.55 6,091.65 1.55 0.52 2.70 1.24CK 8,941.65 6,121.80 8,706.90 1.03 - 1.46 Note: TWC: total water consumption; WUE: water using efficiency; IWUE: irrigation water using efficiency. The same is as in the following tables.
③ Irrigation methods• AI: aerobic irrigation, as recommended for SRI• AWD: alternative wetting and drying• SWD: shallowwetdry sequential management
Impact of water-saving techniques• The technical approach includes: – Tillage, nursery usage, water and fertilizer management.• Significant quantities of water have been saved.• Traditional water consumption in paddy fields was 9,795.2 m3/ha, with 8,279.85 m3/ha of this being irrigation water.• Water productivity was 0.82 kg/m3, and the irrigation water use efficiency was 0.97 kg/m3.
Water balance in paddy field and water requirement (modified SRI)2.07mm/d 1,717.8 m3 Evaporation Rainfall Rainfall Spilled 202.5 m3 Water 稻田 Irrigation requirement for Drainage paddy rice6,364.4 m3 Water saving: 2,193m3/ha (22.04%) leakage WUE = 1.12 kg/m3 1.89 mm/d + 0.30 kg/m3 IWUE = 1.34 kg/m3 + 0.37 kg/m3
3. Prospects of water management • Rice and water management • Future trends in crop cultivation • Key research subjects for water saving in rice cultivation
Rice and water management• Rice is the world’s most important food crop and a major staple food. – China’s 31.7 million ha of rice fields, which account for 20% of the world’s rice area, produce about 35% of total rice grain.• Rice consumes large quantities of irrigation water, up to about 90% of the total water for all crops.• However, fresh water for irrigation is becoming scarce because of increasing competition from urban, industrial, and environmental factors.
• Water limitations threaten the sustainability of irrigated rice systems in many countries.• Rice offers great potential for saving irrigation water because its physiological water requirement (4500 m3 water/ha) is much less than what is currently (incorrectly) considered to be needed and than what is currently applied.• Water-saving rice-cultivation methods are urgently needed to keep up with future food demands, while at the same time they are important for ensuring the future viability of rice production systems.
Future trends in crop cultivation• To promote sustainable development in agriculture, China must simplify the cultivation process, reduce the water requirement, and lighten the workload.• Direct sowing of rice and ratooning will be popular, but some agronomic questions must be answered.• Agricultural machinery must be introduced into all crops cultivation.• SRI is not a fixed technology, but rather a set of ideas for creating a more beneficial growing environment for rice. – We expect further modifications and improvements
Key research subjects for water saving in rice cultivation• Water balance in paddy fields and water requirements in different ecosystems. – The growing of rice should be based on scientific knowledge and consider following factors: regional ecological conditions, cropping systems, natural rainfall, available irrigation resources, and so on.• Varieties for drought tolerance and screening methods. – There is considerable difference among varieties for their drought tolerance. Some can be suitable in arid areas or areas with more uncertain water availability.
• Sensitive growth stages for water stress and their influence. – Limited water resources to be allocated for use during rice’s most sensitive growth stages. Natural rainfall needs to be used as efficiently as possible, and the water demands for rice growing should be reduced as much as possible.• Engineering approach for saving water. – Increased water conservation projects in hilly regions should be pursued, along with reductions in water losses in irrigation channel systems; appropriate use of groundwater warrants systematic development.