Rice is the staple food for the majority of the population in developing countries and therefore crucial for food security. The System of Rice Intensification (SRI) is gaining popularity due to its high potential in increasing rice yield and protecting natural resources. SRI is a flexible set of practices aiming to provide the best environment for the rice plant to utilize its potential, thereby improving the productive efficiency of land, labor, water, nutrients and capital. Therefore it is emerging as a potential alternative to flooded rice cultivation, and the number of farmers practicing some or all SRI principles is steadily increasing.
Background
SRI was originally developed by the French priest Henri de Laulanié in the highlands of Madagascar during the 1970s and 1980s. During a 1983 drought, which prevented many farmers from flooding, he noticed that the rice plants and their roots showed unusually strong growth. The Cornell International Institute for Food, Agriculture and Development (CIIFAD) started to work with de Laulanié in 1994 and supported the spread of SRI from Madagascar around the world.
The Concept of SRI
The System of Rice Intensification is understood as a set of principles and a set of mostly biophysical mechanisms. It is not a standard package of practices, according to site-specific conditions ways of interpretation and application may vary as does the formulation of principles and practices in different sources. Farmers are encouraged to experiment in their own fields to find the best suitable practices. Variants of SRI have also been tested in which only some of the basic components were practiced (Ly et al. 2012, Dobermann 2004, Stoop et al. 2002).
Major SRI Principles include:
- Early, quick and healthy plant establishment
- Reduced plant density
- Improved soil conditions through enrichment with organic matter
- Reduced and controlled water application (SRI Rice, http://sri.ciifad.cornell.edu)
According to site-specific agroecological and socioeconomic conditions, farmers can adapt recommended SRI practices:
- Transplanting 8-15 days old seedlings,
- Transplanting the seedlings at wide plant spacing (at least 25 x 25 cm from plant to plant) to encourage greater root and canopy growth
- Planting of single seedlings rather than in clumps. Transplant them horizontally, carefully and gently. In contrast to plunging clumps vertically into the soil with the root tips pointing upwards, this method allows the root to grow downwards quickly.
- Move from permanent flooding to intermittent irrigation to improve oxygen supply to rice roots, thereby decreasing aerenchyma formation and causing a stronger, healthier root system with potential advantages for nutrient uptake.
- Increased use of organic fertilizer to enhance soil fertility (compost instead of chemical fertilizer)
- Manual or mechanical weed control instead of herbicide use. By using a mechanical rotary weeder, the soil will be w aerated, stimulate soil biota and strengthen the nutrient fixation in the soil.
The concept of SRI bases on creating the best conditions for the single plant. Stoop et al. (2002) provides more detailed information about the plant physiological and ecological factors of the SRI.
Yields and Economic Impacts
Multiple sources have reported that SRI is capable of producing considerably higher rice yields. 2011 an Indian farmer set a new world record in rice production of 22.4 tons per hectare using SRI(http://www.agriculturesnetwork.org/resources/extra/bihar-sri).
Uphoff (2007) reviewed the results from eleven evaluations in eight countries and reported an average yield increase of 52% in SRI compared to conventional practices, the cost of production was 24% lower and the net return was 128% higher. Within a farm survey in Mwea Irrigation Scheme, Kenya, the yield under SRI increased by 1.6 t/ha (33%), with seed requirements reduced by 87% and water savings of 28% compared to Farmers Practice (Ndiiri 2013).
The German Government funded Project “Poverty Alleviation in Rural Areas” (PARA) promoted and supported the implementation of SRI farming practices in Trà Vinh Province, Vietnam, during four crop seasons between late 2011 and early 2013. Farmers could increase profits through SRI by an average of 155%. The SRI Plot yields were up to 18% higher than those of the control plots, and due to the fine quality of SRI Rice, a 20% higher price could be received in the third and fourth crop season (GIZ 2013a).
The publication “Rice Cropping Systems and Resource Efficiency” reviews the available scientific literature and gives a more detailed summary of yields and economic impacts achieved by SRI compared to other rice cropping systems from various sites.
The economic impacts of SRI adoption are very context specific and depend on micro-level socioeconomic and agroecological conditions (GIZ 2013b). For example farmers have no incentive in saving water where irrigation water and electricity for pumping water are available free of charge.
Different other methods like “Alternate Wetting and Drying” (AWD), which shares water management characteristics with SRI, have emerged partly in response to SRI.
Furthermore, the SRI principles have in the meantime been applied to other crops, such as wheat, sugarcane, teff, finger millet, pulses, showing increased productivity over current conventional planting practices. The general term “System of Crop Intensification (SCI)” has emerged to apply to this next generation of agroecological innovation.
Environmental Impacts
Water
Facing the consequences of climate change on the availability of water and recognizing that agriculture plays a significant part in increasing water scarcity, possible water savings are promoted as a key benefit of SRI.
With the SRI – Method of intermittent irrigation, “only a minimum of water is applied during the vegetative growth period. During flowering a thin layer of water is maintained, followed by alternate wetting and drying in the grain filling period, before draining the paddy 2-3 weeks before harvest” (SRI Rice, http://sri.ciifad.cornell.edu). This description implies that substantial water-savings are possible with SRI.
In the Senegal River Valle, Krupnik et al. (2012) recorded water savings between 16 % and 48 % in a five season field experiment comparing SRI with the recommended management practices. A reduction of 57% in irrigation water use and a 91% increase in water use efficiency for SRI plots compared to conventional flooded rice is reported in Zhao et al.(2010) (cited in GIZ 2013b). This underlines that substantial water savings and thus increases in water productivity can be achieved with SRI.
The application of SRI not only decreases water consumption, it has benefits for water quality due to the lower chemical fertilizer and pesticide use.
Soil Quality
Soil pore volume increases due to repeated wetting and drying, and the application of organic matter increases C and N contents and microbial biomass. Mechanical weeding
will aerate the soil, stimulate soil biota and strengthen the nutrient fixation.
Climate Change Mitigation and Adaptation
As a result from non-flooded fields and by using less chemical fertilizer, SRI mitigates climate change by reducing CH4 emissions. Arguments against the systems include that SRI plots emit more nitrous oxide than conventional rice plots, which has adverse effects on climate change. Due to the Method of SRI, plants are strong and healthy and more resilient to pests, diseases and extreme weather conditions. An increased resistance to wind damage is reported in Ndiiri et al. 2013. Thus the risk of crop failure is reduced. This higher resilience is an important feature of climate change adaptation.
Agrobiodiversity
Due to lower use of agrochemicals and the addition of organic matter, SRI contributes to a higher diversity of soil biota and of general biodiversity in and around the rice field. As SRI works with all varieties of rice, it can contribute to maintain a genetic diversity.
Criticism
Besides the described potentials and opportunities of SRI and the successes obtained, some authors still declare doubts. Dobermann (2004) critically discusses the approach of the SRI and claims its little potential for improving the rice production in intensive irrigated systems and favorable soils. His critics are based on the assumption that the too optimistic publications about the SRI rely on an incomplete coverage of literature and a lack of detailed field research following high scientific standards. The flexibility of the SRI also does not allow comparisons to other methods. He doubts the plausibility of reported yields ranging from 15 to 23,4 t/ha, as they are near the climatic-genetic potential and are unrealistic given the maximum achievable radiation use efficiency of rice and the environmental conditions from where they have been reported. In ceilings near the climatic-genetic potential of rice high yields could be achieved rather through the implementation of more cost-efficient management practices, provided that management follows known best practices, than with the techniques proposed in SRI. For example deep root systems are not a necessity for high yields when good water and nitrogen management is guaranteed.
In his opinion it is a “risky management strategy” to give up the long-term benefits of continuous flooding during rice growth, especially where water is not scarce, unless possible long-term consequences for soil fertility and productivity through the SRI are fully understood. Thus, the SRI is mainly a system geared towards rice cropping practiced by resource-poor farmers in uncomfortable environmental conditions, so that its overall impact on the global rice supply may remain small (Dobermann 2004). However, such “resource-pour” conditions itself can be an obstacle for implementing the SRI as intermittend irrigation is difficult to apply in environments with poorly developed infrastructure (Ly et al. 2012). Moreover, the intensive labour inputs are mentioned as a disadvantage of SRI.
References and further information
- Dobermann, A. (2004): A critical assessment of the system of rice intensification (SRI). Agricultural Systems 79 (2004) 261–281
- GIZ 2013a: Promoting the System of Rice Intensification. Lessons Learned from Trà Vinh Province, Viet Nam
- GIZ 2013b: Rice cropping systems and resource efficiency
- Ly, P. et al. (2012): The System of Rice Intensification: Adapted practices, reported outcomes and their relevance in Cambodia. In: Agricultural Systems 113 16-27
- Ndiiria, J.A. et al. (2013): Adoption, constraints and economic returns of paddy rice under the system of rice intensification in Mwea, Kenya. Agricultural Water Management 129 44– 55
- Stoop, W.A., Uphoff, N., Kassam, A. (2002): A review of agricultural research issues raised by the system of rice intensification (SRI) from Madagascar: opportunities for improving farming systems for resource-poor farmers. Agricultural Systems 71 249–274
- Stoop, W.A.; Adam, A;, Kassam, A. (2009): Comparing rice production systems: A challenge for agronomic research and for the dissemination of knowledge-intensive farming practices. Agricultural Water Management 96 1491–1501
- Krupnik, J.T., Shennon, C., Rodenburg, J. (2012): Yield, water productivity and nutrient balances under the System of Rice Intensification and Recommended Management Practices in the Sahel. Field Crops Research 130 155–167
- Uphoff, N. (2007): Reducing the vulnerability of rural households through agroecological practice: considering the system of rice intensification (SRI). Mondes Dqvel. 140, 85–100
- Styger, E. et al.(2011): The system of rice intensification as a sustainable agricultural innovation: introducing, adapting and scaling up a system of rice intensification practices in the Timbuktu region of Mali. International Journal of Agricultural Sustainability 9(1) 2011
- (SRI Rice) : The SRI International Network and Resources Center
