Abstract
Abstract: The soybean cultivar ‘Yukipirika’ was grown and compared under two different conditions: twin-row cultivation (TR), with 75 cm between rows and 20 cm between subrows for 2 years using a special sowing machine, and the conventional cultivation (CR) with 75 cm between rows.Seed yields in 2021 and 2022 were higher under TR than under CR, by 24% and 22%, respectively. The higher seed yield under TR was attributed to an increase in the number of pods associated with an increased number of branch nodes. The latter increase was due to two factors: 1) high total intercepted radiation from vegetative to beginning pod (R3) stages and 2) good community structure, with a low light extinction coefficient and easy penetration of solar radiation into the community in the late reproductive stage, after R3. The increase in intercepted radiation may have affected total dry matter weight by accelerating crop growth, whereas the light-intercepting characteristics of the community during the late reproductive stage may have increased total dry matter weight by improving the net assimilation rate. The same trends were observed both in 2021, a high-yielding year with high solar radiation and spindle-shaped leaf structure, and in 2022, a low-yielding year characterized by high temperatures, low solar radiation, and inverted triangle leaf structure.
