Researchers from National Agriculture and Food Research Organization (NARO) and Ryukoku University have discovered that persistent carbon, which is difficult to decompose, accumulates in soil during cultivation of high-yielding rice by suppressing the application amount of potassium fertilizer . This finding indicates the possibility of artificially promoting the accumulation of persistent carbon in soil by controlling application of potassium fertilizer to rice and is expected to lead to the development of new measures against global warming.
Overview
Various efforts such as applying compost to agricultural land to actively accumulate carbon in the soil as a measure against global warming are being promoted. However, when compost is decomposed by microorganisms, it eventually becomes carbon dioxide and released into the atmosphere. Hence carbon does not accumulate in the soil for a long period of time. On the other hand, it is known that persistent carbon is not easily decomposed by microorganisms and has accumulated in soil for thousands of years. However, the mechanism of persistent carbon accumulation is unknown. It is necessary to clarify the process of formation and accumulation of persistent carbon in soil in order to develop a technology for accumulating carbon in soil. Therefore, NARO and Ryukoku University conducted research on paddy fields and clarified that persistent carbon is formed and accumulated in the soil when high-yielding rice is cultivated by suppressing the application of potassium fertilizer amount.
In paddy fields where high-yielding rice was cultivated with the application of deficient potassium fertilizer, 76.3 kg of persistent carbon per 10 ares accumulated in the soil over 11 years. Meanwhile, persistent carbon did not accumulate in paddy fields where Koshihikari was cultivated with sufficient potassium fertilization. From the nutrient balance of paddy fields and the survey of rice roots and soil, it was revealed that
- High-yielding rice absorbed the required amount of potassium from other sources and grew normally, even if the supply of easily absorbable potassium derived from fertilizer, irrigation water, and soil was insufficient due to suppressing the application of potassium fertilizer.
- High-yielding rice roots break up the minerals in soil and release their constituent elements potassium, silicic acid, and aluminum.
- High-yielding rice absorbs potassium and silicic acid released from minerals, and aluminum remains in the rhizosphere.
- Aluminum combines with carbon in soil to form and accumulate persistent carbon
On the other hand, in the Koshihikari cultivated paddy field where potassium fertilizer was sufficiently supplied, minerals were not used, and persistent carbon was not formed. This result indicates that it is possible to artificially promote soil accumulation of persistent carbon by controlling application of potassium fertilizer to rice, which is expected to lead to the development of new global warming countermeasure technology.
In the future, we plan to investigate whether the ability to utilize potassium and silicic acid in minerals varies depending on the rice varieties, and regarding the application of compost to further increase the accumulation of persistent carbon.
Reference Information
K.Kusa, M.Moriizumi, S.Hobara, M.Kaneko, S.Matsumoto, J.Kasuga and N.Ae. Mineral weathering and silicon uptake by rice plants promote carbon storage in paddy fields. 2021, 67(2), 162-170: Soil Science and Plant Nutrition. doi10.1080/00380768.2021.1878471
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