Pre-germinated seeds or seedlings are directly planted in soil or broadcast in flooded field under this technology. Rice cultivation is responsible for 10% of GHG emissions from agriculture. In developing countries, the share of rice in GHG emissions from agriculture is even higher, e.g., it was 16% in 1994.
Direct seeding of pre-germinated rice has resulted in to the reduced methane emissions due to a shorter flooding period and decreased soil disturbance compared to transplanting rice seedlings. Ko and Kang (2000) demonstrated that in South Korea, where the common cultural practice is to transplant 30-day-old seedlings, that significant reductions in methane emissions could be achieved by direct seeding on wet soil (8%) and on dry soil (33%) with no significant effect on yields in either case. Similarly, Metra-Corton et al., (2000) showed that direct seeding resulted in a 16-54% reduction in methane emissions compared to that of transplanted rice seedlings. For six different cases, Wassman et al. (2000) reported a 16-92% reductions in methane emissions with direct seeding compared to transplants, for six rice cultivars, however, a yield reductions of 4-36% was also observed. Subsequently, Huang et al. (2012) found no significant effect on yield over six growing seasons, when a treatment of no-tillage + herbicide + broadcast of pre-germinated seeds on flooded field was compared to conventional tillage + later flooding + transplants, but at the end of the fifth year, increased in organic carbon in the top 5cm of soil was approximately matched by reductions in carbon at deeper depths.
Feasibility of technology and operational necessities
Transplanting is the most common method for paddy rice production in Asia, whereas direct seeding is common in Australia and the United States. In Asia, it is traditional to use transplants, so there is resistance to change to direct seeding. However, before habits can change, it must be consistently demonstrated that yields will not be significantly decreased by direct seeding.
Status of the technology and its future market potential
- Direct planting is faster and less labour-intensive than transplanting.
- It reduces land preparation time.
- Yields reduced in some instances (e.g., Hossain et al., 2002; Wassman et al., 2000)
- More lodging of rice plants (De Datta, 1986).
How the technology could contribute to socio-economic development and environmental protection
Weerakoon et al. (2011) surveyed Sri Lankan farmers and presented the cost of cultivation for direct wet-seeded rice in three scenarios: dry zone irrigated, intermediate zone irrigated and wet zone rain fed (figure 1). They found that under irrigated conditions direct seeding was profitable, whereas under rain fed conditions, gross returns were about half than under irrigation, and the direct seeded cropping system was not profitable.
Figure 1: Economics of wet-seeded rice in Sri Lanka (source: Weerakoon et al., 2011)
Financial requirements and costs
According to Wassmann and Pathak (2007), costs of emissions saving through direct seeding was found to be more than US$35 per tCO2e saved.
- De Datta, S.K. (1986): Technology development and the spread of direct-seeded flooded rice in southeast Asia. Experimental Agriculture, 22(4):417-426.
- Hossain, M.F., Salam, M.A., Uddin, M.R., Pervez, Z., and Sarkar, M.A.R. (2002). A comparison study of direct seeding versus transplanting method on the yield of aus rice. Pakistan Journal of Agronomy 1:86-88.
- Huang, M., Zou, Y., Jiang, P., Xia, B., Feng, Y., and Mo, Y. (2012). Effect of tillage on soil and crop properties of wet-seeded flooded rice. Field Crops Research 129:28-38.
- Ko, J.Y. and Kang, H.W. (2000): The effects of cultural practices on methane emission from rice fields. Nutrient Cycling in Agroecosystems 58: 311–314.
- Metra-Corton, T.M., Bajita, J.B., Grospe, F.S., Pamplona, R.R., Asis, C.A., Wassmann, R. and Lantin, R.S. (2000): Methane emission from irrigated and intensively managed rice fields in Central Luzon (Philippines), Nutrient Cycl. Agroecosys. 58, 37-53.
- Wassman R., Lantin R.S., Neue H. U., Buendia L.V., Corton T.M. and Lu Y.(2000): Characterization of methane emissions from rice fields in Asia. III. Mitigation options and future research needs. Nutrient Cycling in Agroecosystems 58: 23–36.
- Wassmann, R. and Pathak, H. (2007): Introducing greenhouse gas mitigation as a development objective in rice-based agriculture: II. Cost- benefit assessment for different technologies, regions and scales. Agricultural Systems 94:826-840.
- Weerakoon, W.M.W., Mutunayake, M.M.P., Bandara, C., Rao, A.N., Bhandari, D.C., Ladha, J.K (2011): Direct-seeded rice culture in Sri Lanka: Lessons from farmers. Field Crops Research, 121(1):53-63.