Impact of Sowing Date on Productivity and Quality of Lobo Radish Cultivars (Raphanus sativus L. Convar. Lobo) During Summer Cultivation

Lobo radish yield and quality depend heavily on summer sowing dates. A three-year field trial (2022–2024) in the Central Forest-Steppe of Ukraine evaluated four sowing dates–D1 (first decade of July), D2 (second decade of July), D3 (third decade of July), and D4 (first decade of August)–for cultivars Troiandova and Lebidka. Sowing in late July (D3) was optimal, securing maximum marketable yield (42.2 t·ha−1 for Troiandova, 38.9 t·ha−1 for Lebidka), peak marketability (70.5–72.0%), and minimal bolting (2.1–2.8%). Early sowing dates (D1–D2) increased bolting (up to 20.0%) and pest damage by cabbage root fly (Delia radicum L., 25.1–27.3%), reducing marketability to 45.4–52.0%. August sowing (D4) reduced root weight (204.6–224.3 g) but increased dry matter (8.6–9.8%) and soluble sugars (4.8–5.5%). AMMI and GGE biplots revealed higher yield stability for cultivar Lebidka (notably at D4), whereas Troiandova was highly responsive to optimal conditions (Troy-D3). Overall, sowing in the third decade of July (D3) is recommended for commercial production.