Responses in the productivity and agronomic traits of new black oat cultivars between different sowing seasons in the warm regions of southwest Japan

Abstract Black oat ( Avena strigosa Schreb.) is an important grass species that is commonly used as fodder and green manure in Japan. Consequently, it is agriculturally important to understand the changes in productivity and agronomic traits caused by differences in the sowing time for oat cultivars used throughout several growing seasons. In this study, the productivities and agronomic traits were evaluated for two black oats cultivars, namely “Ricky” and “Terara,” which were recently developed as early cultivars in Japan. These characteristics were examined under both late‐summer and spring sowing conditions in a warm region of Japan to evaluate their response patterns to different sowing seasons. The 3‐year mean dry matter yield of “Ricky” was 75.3 kg/a under late‐summer sowing conditions and 86.7 kg/a under spring sowing conditions, representing an 18% higher yield under spring sowing conditions. For “Terara,” three‐year mean dry matter yield was 69.4 kg/a under late‐summer sowing conditions and 76.3 kg/a under spring sowing conditions, representing a 10% higher yield under spring sowing conditions. These results indicate that both cultivars were more productive when sown in spring. The number of days from germination to heading did not differ between the two conditions for “Ricky” but was significantly earlier (5.2 days) under late‐summer sowing conditions in “Terara.” In addition, the plant height was higher (17 cm) under spring sowing conditions for “Ricky,” whereas no difference was observed for “Terara.” These results demonstrated that the response patterns of agronomic traits caused by different sowing times differed between cultivars classified as the same early cultivar. “Ricky” and “Terara” showed stable productivity under both late‐summer and spring sowing conditions in the warm regions of Japan. “Ricky” consistently showed higher yields, while “Terara” performed comparably to commercial cultivars. Their nematode‐suppressing traits could further support their potential as dual‐purpose grasses for fodder and green manure.