Carbon Sequestration of Green Manure
The main sources of GHG emissions of the Food and Agriculture Industry are from the “rice planting” and “crop residue burning” on the farmland, and the “agricultural soil,” “lime treatment,” and “urea application” for soil fertilization. Among them, the “agricultural soil” in soil fertilization accounts for the highest proportion of emissions.
In common agricultural practices, chemical fertilizers with fast effectiveness are widely used. However, it is just because of the variety of elements in chemical fertilizers that the remaining components may change the soil physicochemical properties after long-term accumulation. These remaining components can even go into the aquaculture fishery or domestic water from the irrigation and drainage systems, causing water pollution. The so-called green manure crops refer to any plant that can be directly or indirectly used as fertilizers or soil improvement for having the functions of increasing soil nutrients, organic matter, improving soil physicochemical properties, and reducing soil erosion. The specific effect of green manure is detailed in the following.
| Efficacy | Content |
| Improve Soil Physiochemical Nature | The green manure crops are cultivated to be incorporated into the soil while still green, and when their cellulose, lignin, and other substances that are difficult to compose are combined with the soil clay particles to form soil colloidal composites after humi-fication, the soil temperature and soil buffer capacity are improved. |
| Promote the Activity of Beneficial Microorganisms in the Soil | Green manure residues (organic substances) can provide microorganisms with nutrients and energy, balance soil microbial populations, reduce and avoid the reproduction of pathogenic bacteria, and increase crop disease resistance. |
| Covering Soil | The main roots of leguminous green manure crops go deep into the soil layer, and the organic matter in the roots and plant residues have the function of cementing soil that can consolidate the soil and accumulate water and nutrient in the soil. |
| Reduce the Occurrence of Pests and Diseases | Green manure crops can change the composition of organic matter in the rhizosphere soil to maintain a stable ecosystem and increase the activity of soil microorganism, reducing the pathogenic bacteria or pests population in soil, and the problem of soil sickness can be improved, the toxic substances can be decomposed, and the accumulation of toxic substances in the soil can be reduced. |
| Enhance the Water Contention Capacity of Soil and Improve the Drought Resistance of Crops | Humus is loose and porous hydrophilic colloid that can absorb a large amount of water and improve soil permeability so as to provide crops with more effective water. |
| Reduce Pollution From Pesticide and Heavy Metal | Brown humic acid enables the increased solubility of some pesticides remained in soil, such as DDT, triazine, etc., and it can accelerate their leaching. In addition, it can also produce water-soluble complexes with certain metal ions to allow toxic metal ions to be discharged from the soil with water, reducing the harm to the crops and pollution to the soil. |
TSC has a vast planting area of sugarcane, making it an indispensable carbon pool. The Sugar Business Division also plants leguminous crops such as Sesbania and Sun Hemp after the harvest of sugarcane and before the planting period. The nitrogen fixation characteristics of legumes can reduce the use of nitrogen fertilizers afterwards, beneficial to the reduction of GHG emissions. During 2022/2023, the total planting area of green manure crops totals 444.28 hectares (241.96 hectares in Shanhua Plant and 202.32 hectares in Huwei Plant).
- Green manure crops are mainly planted on fallow land where perennial roots no longer stay after the harvest of sugarcane (4-6 months). However, part of the land will be released for lease (provided to melon farmers to grow melons or other short-term crops), as the weeding area, for the sugar factories to put scraps (filter mud, bagasse, soot), and for the application of alkaline materials like oyster shell powder to improve the acidic soil. Therefore, green manure plants are not planted on every piece of fallow land. In addition, due to the influence of climate change, the rainfall in spring decreases. Therefore, the fallow land that lacks a fixed source of water for irrigation is not suitable for the planting of green manure crops. To respond to the demand for energy conservation and carbon reduction, the Sugar Business Division plans to properly increase the planting area of green manure crops so as to reduce the application of chemical fertilizers and increase the organic matter and soil carbon storage of the soil on sugarcane farms.
- In regard to the quantitative benefits of planting green manure crops for carbon storage, according to the data of the agricultural research and extension station, based on the condition of fresh weight at 25,000kg/hectare on the land where Sun Hemp is planted and the nitrogen mineralization rate at 80%, the Sun Hemp is planted followed by the nitrogen fertilization management, about 1/3 or 1/2 of the amount of fertilizers can be reduced compared with soil without green manure application. Furthermore, in accordance with foreign literature, rotation planting of green manure crops with corn for 12 years can averagely fix 1.3 tonnes/hectare of carbon into soil every year. It was originally estimated that the rotation of green manure crops and sugarcane on an area of 444.28 hectare, 577.54 tonnes of carbon can be stored in the soil of the sugarcane field. However, the actual data often require the inventory of data of overall land with green manure crops over the years to obtain objective and quantitative data. Therefore, Sugar Business Division and the Taiwan Sugar Research Institute (TSRI) proposed the research plan, and the academic community was commissioned to establish the methodology and benefits of soil carbon sinks.
Promotion of Organic Cultivation
Organic farming is an environmentally friendly and sustainable model for agricultural production. Starting from 2000, TSC has strictly selected high-quality farms as organic rice cultivation bases. In addition to actively develop our own organic crop cultivation zones, we also continue the trial planting and mass production of economic crops. In 2023, the self-operated organic rice certification area reached 88.79 hectares. The main market includes schools & group meals, convenience stores and chain channels. Furthermore, in line with the government's promotion of the new agricultural policy to advocate organic farming, as of the end of December 2023, the Company has provided the government 312 hectares (12 cases) of leased land for the establishment of a special zone for organic agriculture. Additionally, the Company continues to support the promotion and cultivation of organic agriculture through leasing arrangements, offering organic farmland, greenhouse facilities, packaging rooms, and refrigeration equipment for lease to professional farmers or agricultural enterprise groups. As of the end of December 2023, the leased area amounted to 1,302.29 hectares, encompassing a total of 196 cases.
