Characteristics of dry matter production in rice plants, cultivar Takanari sown directly in submerged paddy field compared with conventionally transplanted plants [Japanese]

摘要

Dry matter production and the related characters in the rice plants sown directly in the submerged paddy field or in the drained field after puddling were compared with those in conventionally transplanted plants using Takanari as a lodging-resistant cultivar in 1999, 2000 and 2001. The planting density was 42.0, 51.3 and 51.3 hills m(-2), one plant in each hill in 1999, 2000 and 2001, respectively, for the direct-sown plants and was 66.6 (22.2 hills), 66.6 (22.2 hills) and 52.5 (17.5 hills) m(-2) in 1999, 2000 and 2001, respectively, for the transplanted plants. The grain yield was higher in the direct-sown plants. This resulted from the higher dry matter production due to higher crop growth rate from the tillering to ripening stages. During the tillering stage, the leaf area index (LAI) increased rapidly owing to the production of larger number of tillers in the direct-sown plants. This caused the larger interception of solar radiation of the canopy. After the panicle formation stage, the canopy of the direct-sown plants consisted of more erect leaves, yielding a lower value of extinction coefficient and keeping high net assimilation rate in spite of the larger LAI. The direct-sown plants produced a larger number of crown roots, and accumulated a larger amount of nitrogen. The leaf color degradation of lower leaves on a stem was smaller in the direct-sown plants after heading. These also might contribute to the higher dry matter production in the plants.