For upland crops, reduced tillage technology for paddy rice involves planting or transplanting directly into the soil with minimal prior tillage in the residues of the preceding crop. 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.
See 'Rice production technologies' for an overview of all climate change mitigation technologies related to rice cultivation.
Methane emissions at the tilling stage of rice field preparation account for more than 80% of total annual emissions. Wet-land tillage compared to dry-land zero-tillage results in an earlier onset of methanogenesis and, therefore, contributes to greater methane production during the growing season. Zero-tillage results in the lowest methane emissions and is a practice which utilises crop residues in place of compost or mulch. This is often done by hand transplanting, but mechanical rice transplanters that can transplant small seedlings into flooded soil are becoming popular in developed countries like Japan and South Korea. Following about a week after an herbicide application, broadcasting of pre-germinated seeds into the flood water is also done (Huang et al., 2012).
Zero-till for paddy rice production is not widely practiced. Zero-till with its more costly machinery has become prevalent only in richer countries whose farmers can afford equipment like mechanical transplanters. However, use of herbicides has enabled broadcasting of pre-germinated seed, but lack of familiarity with reduced tillage techniques is a major constraint for small, poor farmers.
- Less labour required.
- Farmers do not require as much time for the preparation of the field for the next crop.
- As less time is required for field preparation, water can be conserved or alternatively, the plant growth period can be lengthened, allowing the use of longer-season varieties with higher yield potential.
- Methane mitigation through reduced tillage provides protection of the soil and improves its condition.
- Rice cultivation under reduced tillage makes it vulnerable to harmful pests such as the stem borer which survive on the unincorporated residue or stubble.
- Deploying new machinery for reduced tillage and training to farmers is a long-term endeavor and involves considerable expenditure.
- Minimum tillage practices require increased use of herbicides and are, therefore, less acceptable.
- Lower germination with reduced tillage necessitates higher seeding rates and therefore higher seed costs.
Tilling causes 80% of methane emission, therefore, reduced tillage improves the mitigation potential of methane. However, the high cost of mechanical transplanters restricts deployment, although use of herbicides and broadcasting of pre-germinated seed greatly improves the economic gains for small farmers.
Zero-till with its more costly machinery has become prevalent only in richer countries whose farmers can afford equipment like mechanical transplanters.
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.