In this feature article, Narottam Dey calls for renewed interest in indigenous rice lines to counter the erosion of the crop's genetic diversity. Given the high degree of genetic heterogeneity and a long evolutionary history, rice landraces have proven to be highly adaptive to diverse environmental conditions and are believed to harbour a number of valuable genetic resources for crop improvement. He argues that the Green Revolution led to the development of a number of high-yielding rice varieties (HYVs) that require both irrigation and fertilizer management and specific cultivation practices to achieve their full yield potential. The widespread use of these high-yielding rice lines has led to the premature abandonment of many indigenous lines. Dey believes the only way to popularise and utilize indigenous lines in future breeding programmes is through the development of a databank with detailed agro-morphology, physio-biochemical and molecular screening with trait-linked markers and specific genes. Many research laboratories are working on improving the knowledge base and a number of promising lines are being utilized in breeding through marker-assisted selection.With regard to sustainable rice production, Dey concludes that if efforts are not made now to conserve and characterize extant landraces, the result will be a further marked reduction in the diversity, a narrowed genetic base, and eventually the genetic vulnerability of these species. Depending on a few selected HYVs is not an option for the future of food and farming and for sustaining livelihoods. It is also a food sovereignty issue that urgently needs to be addressed in responding to the global challenge of improving food and nutrition security.
In this feature article, Sheng Zhou and Xiangfu summarize some realistic methods for reducing methane emissions in rice production. They present some case studies of efforts to mitigate methane emissions, such as irrigation management, the use of suitable rice cultivars (e.g. water-saving and drought-resistant rice, WDR) and combinations of different fertilizers. The production, oxidation and transport of methane in rice fields are influenced by many factors, including the rice cultivars, the cultivation system, water regimes practiced, and types of fertilizer. Simultaneously, soil carbon sequestration in rice fields is a key potential approach for turning rice fields from being a source of greenhouse gas emissions to being a carbon sink.The authors describe how and how much methane is produced from rice paddies, and give examples of mitigation measures. Promising techniques include water management, organic amendments during the growing season, fertilization regimes and the use of appropriate rice cultivars, with the first two having the greatest impact. Mid-season drainage, intermittent irrigation or pre-harvest field drying may also reduce methane fluxes. The first case study details mitigation by water management and choice of rice cultivar, while the second explains the potential of different combinations of fertilizers. The authors conclude that low-carbon rice production requires combining available mitigation options into comprehensive packages. Knowledge of the soil microbe communities associated with the leading rice cultivars is essential for recommending appropriate mitigation strategies.
In this new article, Fallou Sarr reflects on the post-harvest knowledge system for rice in Senegal. He note that rice occupies a prominent place in Senegal's economy and in food consumption for both urban and rural households. Since independence, rice consumption has increased by almost 1,000%, reaching 1 million t of milled rice. Paddy rice production is the responsibility of farmers in irrigated areas and rain-fed areas However, the collection of paddy rice, in irrigated areas, is an activity undertaken by traders, rice millers and farmers while, in rain-fed areas, it is mainly carried out by women and children (more than 90% in the Southern area) and with carts (70% to 80%, in the Central area). Factories find it difficult to secure large quantities of paddy rice in a single collection area in the Senegal River valley, Sarr acknowledges that there is a clear difference between both rice cultivation systems and this is also reflected in post-harvest losses. However paddy drying is critical for both systems with losses ranging from 5 to 10%. Irrigated systems face two additional critical issues: paddy rice harvest (ill-adapted harvesters) and drying (insufficient drying areas). On the other hand in rain-fed systems, threshing losses, which is mainly manual, represents the stage where most post-harvest losses are recorded (40 %). Sarr emphasizes three intervention areas for improving the post-harvest knowledge system; research, government & universities and regional organizations.For research, Sarr recommends that they systematically assess post-harvest losses at all stages of the rice value/supply chain, to indicate critical points and the best ways to address them; study, experiment and disseminate local knowledge on rice post-harvest handling (rice conservation/storage) and adapt technological innovations for greater efficiency, effectiveness and accessibility (harvester, thresher, sorter). With respect to the government and universities, he recommends that a national programme entirely focused on improving rice post-harvest systems (equipment, infrastructure, processing, training, organisation, marketing, access to credit) be developed. For regional organisations such as CORAF/WECARD, Sarr recommends that they include more projects specific on post-harvest treatment in their food crops programmes.
This lead article outlines the benefits of the SRI system, in particular alternate wetting and drying irrigation (AWD), which allows a 20-50% direct reduction of irrigation water applied to the rice paddy. Under the current practice of continuously-flooded rice paddies, rice crops receive two to three times more water than other irrigated cereal crops, even though rice has a similar transpiration rate. Developing methodologies that improve water-use efficiency or water productivity in rice production will allow for saving water and for its reallocation to other uses. The SRI system is co-responsible for saving water and increasing yields. SRI also focuses on improving plant establishment, significantly reducing plant population and improving soil conditions. To follow SRI practices, farmers are prompted to pay attention to land levelling, so as to avoid drowning the small transplants with irrigation water. Land levelling is thus an important water-saving practice, as it allows even distribution of water throughout the plot, and the depth of the irrigation water can be precisely controlled. Changes in production cost and labour allocations occur with SRI compared to the conventional system; however, there are challenges. An effective extension and advisory system is key.Photo/credit: Erika Styger
This lead article describes the experiences of SNV in strengthening the rice value chains in Vietnam, Lao PDR and Cambodia. It especially considers the role of the traditional knowledge system and the changes and adaptations associated with responding to market developments and private sector involvement. It also analyses how the actors in the value chain use both traditional and scientific and technological knowledge in a changing environment.Through natural selection and farmer knowledge, a wide collection of rice varieties has been preserved. However, since the introduction of intensive irrigation combined with intensive use of chemical fertilisers and high-yielding varieties, farmers have become increasingly dependent on external knowledge sources, but are not receiving adequate advisory services. Improving interaction between farmers and the private sector is considered crucial for meeting demands of international markets, given the need for delivering homogeneous quality on a consistent basis and in a cost effective manner.