The Influence of Planting Density on the Flowering Pattern and Seed Yield in Peanut (Arachis hypogea L.) Grown in the Northern Region of Japan

In peanut cultivation in the Tokachi region of Hokkaido, Japan, it is essential to complete the harvest by early October to prevent frost damage. Therefore, cultivation methods that can accelerate the flowering period are necessary. It is understood that planting density can influence the timing of flowering, with crops often flowering earlier at higher densities. This study aimed to investigate whether growing peanuts at higher densities could advance the flowering period and, consequently, enhance yield. The Japanese peanut variety, Tachimasari, was cultivated in 2022 and 2023 at a conventional planting density of 5.8 plant m−2 (D5.8) and at density conditions of 8.7 plant m−2 (D8.7) and 11.6 plant m−2 (D11.6). The D8.7 and D11.6 plants reached the peak of flowering 2.8 and 5.1 days earlier, respectively, and the end of flowering 3.7 and 8.0 days earlier than the D5.8 plants. Although the total number of flowers was higher in D5.8, pod fertility was greater in D8.7 and D11.6, where plants were able to reduce the occurrence of ineffective flowers and immature pods. Consequently, higher seed yields were observed in D8.7 (2709 kg ha−1) and D11.6 (2754 kg ha−1), where lower individual productivity was offset by higher planting densities, compared to the conventional density condition of D5.8 (2169 kg ha−1).